Download MBBS Biochemistry PPT 48 Carbohydrate Metabolism Lecture Notes

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Carbohydrate

Metabolism

Synopsis

Introduction to Metabolism
Ingestion of Carbohydrates
Digestion and Absorption Of Carbohydrates.
Transportation and Uptake of Glucose by cells.
Utilization/Assimilation of Carbohydrates.
Fate of Glucose ,Galactose and Fructose
(Associated Anabolic and Catabolic Pathways)
Excretion Of Metabolic end products of Carbohydrates
Applied aspects/Associated Metabolic

Disorder/Inborn Errors of Carbohydrate Metabolism.
Various Fates of Glucose/Metabolic

Pathways Associated to Glucose.

Complete Oxidation Of Glucose

1.

Glycolysis and Rapaport Leubering

Cycle

2. PDH Complex Reaction
3.

TCA cycle

Glycogen Metabolism

1. Glycogenesis
2. Glycogenolysis

HMP shunt/Pentose Phosphate

Pathway

Gluconeogenesis
Cori's Cycle/Glucose Alanine Cycle.
Blood Glucose Regulation
Glucose Tolerance Test (GTT)
Glycosuria
Diabetes Mellitus.
Galactose metabolism
Galactosaemia
Fructose Metabolism
Essential Fructosuria

Irreversible Reactions-

Different set of Enzyme required.
Non equilibrium Reactions.
Regulatory steps.

E2

C

D

E3


Types Of

Biochemical Reactions

Oxidation/Dehydrogenation

/Hydroxylation

Reduction
Hydrolytic
Carboxylation
Decarboxylation
Phosphorylation
Dephosphorylation
Amination
Deamination
Isomerization
Hydration
Dehydration

Metabolic Pathway

Metabolic pathway is a series of

well defined and significant

biochemical reactions followed

one after another giving

intermediate products and finally

end product of the pathway.
A Precursor of the pathway (A)
E1

B
E2
C Intermediates of the pathway (B,C,D)
E3

D
E4

E End Product of the pathway (E)

Organization of Pathways

Pathways consist of sequential steps.
The enzymes may be separate.
May form a multienzyme complex.
May be a membrane-bound system.
New research indicates that

multienzyme complexes are more

common than once thought.


Mutienzyme complex

Separate

enzymes

Membrane

Bound System

Organization of Pathways

Closed Loop

(intermediates recycled)

Linear

Spiral

(product of rxns

(same set of

are substrates for

enzymes used

subsequent rxns)

repeatedly)


Compartmentalization Of

Metabolic Pathways

Compartmentalization

of pathways permits

integration and

regulation of

metabolism.


Phosphoryl-group Transfer

Types Of Metabolic Pathway

Catabolic/Degradative /Energy

Generating/ATP producing

Pathways/Exothermic.

Anabolic/Synthetic/Energy Utilizing/
ATP Using Pathways/Endothermic.
Catabolic pathways involve

oxidative reactions producing

reducing equivalents-

NADH+H+ and FADH2.

Catabolic pathways converge to

few end products.

Anabolic pathways

diverge to

synthesize many

biomolecules.

.



Some pathways serve

both in catabolism and

anabolism ,those are

Amphibolic pathways.

Amphibolic Pathways occur at

the crossroads of metabolism.

Amphibolic pathways links

between Anabolic and Catabolic

pathways.
Regulation of Metabolic

Pathways

Regulation means stimulation and

inhibition of pathways as per

cellular need.

Hormones regulate the metabolic

pathways.

Metabolic pathways are regulated to

allow the organism to respond to

changing conditions.
Every metabolic pathway has its

specific regulatory enzymes/key

enzymes.

Hormones regulate by either

stimulating /inhibiting the

regulatory/key enzymes of the

pathway.

Modes Of Metabolic

Regulation

? Allosteric regulation

? Covalent modification

? Control of enzyme levels

? Compartmentalization

? Metabolic specialization of organs


Feedback inhibition ?

product of pathway down

regulates activity of early

step in pathway

Feedforward activation ?

metabolite produced early in

pathway activates down stream

enzyme
Regulating Related Catabolic

and Anabolic Pathways

Anabolic & catabolic pathways involving

the same compounds are not the same.

Some steps may be common to both
Others must be different - to ensure that

each pathway is spontaneous.

This also allows regulation mechanisms to

turn one pathway onn and the other off.

Modes Of Enzymes Regulation

Alteration in membrane permeability.
Conversion of Inactive to Active form.
Stimulation of mRNA translation.
Induction of new mRNA formation.
Repression of mRNA formation.
Knowledge of normal

metabolism is essential for :

Understanding adaptations of

?Starvation
?Exercise
?Pregnancy and lactation.

Understanding of metabolic

disorders.

Abnormal Metabolism Is Due To

vNutritional Deficiencies
vEnzyme Defects
vHormonal Defects
vDrug and Toxin

Interactions
Normal Enzyme and

Hormonal activities gives

normal metabolism and

health to human body.

Defect in Enzymes and

Hormones derange the

normal metabolism.

Derangement in Metabolism

Any defect or derangement in

normal pattern of metabolism

leads to metabolic disorders.

Mutation in Genes of Enzymes,

forms defective Enzymes.

Congenital defect of Enzyme leads

to Inborn Error Of Metabolism.
Inborn Error Of Metabolism

Congenital deficiency of

any single Enzyme of a

metabolic pathway leads to

Inborn Errors of

Metabolism.

Enzyme Deficiency of a

Metabolic Pathway

Blocks the metabolic reaction.
Blocks the metabolic pathway.
Accumulates and excrete

intermediate product of the pathway.

No formation of end product of the

pathway.

Affects other interrelated metabolic

pathways.
Methods Used to Study

Metabolism

Metabolic Reactions/Metabolic

Pathways were studied :

Using whole organism/Cellular

fractions

Using Metabolic Probes.
Using Radioisotopes.

Ingestion Of Dietary

Carbohydrates
Why To Eat Dietary

Carbohydrates?

Carbohydrates predominantly

not biosynthesized by human

body.

Carbohydrates are required

for metabolic and structural

role to human body.
Precursors for biosynthesis of

nutritionally non essential

amino acids.

To get the role of dietary fiber .
(Cellulose , Hemicellulose ,Pectin

Lignin, Agar)

Carbohydrate is a primary

source of energy and a

preferred fuel of the body.

60-80% of energy intake comes

from Carbohydrates.

Carbohydrate foods are

cheap, readily available and

palatable.
" Fat Burns Under The

Flame Of Carbohydrates"


For the complete oxidation of Fats

there needs Carbohydrates.

How much Carbohydrates To Eat?

OR

Amount Of Carbohydrates To Be

Eaten
R.D.A for dietary Carbohydrates =
400- 600 gm/day

(Depends upon the human activities)

1 gram of Carbohydrate when

completely oxidized in the body

generates 4 kcal of energy.

Calorific value for dietary

Carbohydrates is 4 kcal.
Dietary forms

Of

Carbohydrates

and their

Rich Sources

What Forms Of Dietary

Carbohydrates Eaten?
Dietary Forms Of

Rich sources of Food

Carbohydrates
Monosaccharides



Glucose

Fruits

Honey and Fruits

Fructose
Disaccharides

Sucrose

Common table sugar, Sweets recipes,

Juices, Tea

Lactose

Milk and Milk Products

Maltose

Malt grain ,Germinating seeds

Polysaccharides

Starch

Grains, Pulses, Potatoes, Tubers

,Tapioca

(Predominant)

Glycogen

Meat, Chicken, Liver

(NonVeg Eater)

Cellulose

Whole grains ,Dates, Green leafy

Vegetables ,Raw vegetables,

Cellulose is rich in

unrefined whole grain

(Husk).

Cellulose is poor in

refined grains (Kernel).
Significance Of Cooking

and

Mastication of Food

During cooking there is hydrolysis of

many bonds of food constituents.

Cooking makes the food:

Tasty
Soft
Chewable
Eatable
Easily Digestible
Mastication of food takes place in mouth.

Mastication is biting and chewing of

food with teeth to break large morsals of

food into small particles mixed with

saliva to form bolus.

Proper mastication of food in mouth

facilitates for good digestion and

absorption of food constituents.

Digestion

of

Dietary Carbohydrates

by

Specific Glycosidases
Digestion of carbohydrate involves

cleavage of Glycosidic bonds

present in Polysaccharides and

Disaccharides to form free

Monosaccharides.

Glycosidases are Carbohydrate

Digesting Enzymes which cleaves

specific glycosidic bonds.

There are specific Glycosidases for

each Carbohydrate form.

Digestion of Monosaccharides

Dietary Monosaccharides /

Simple Sugars (Free Glucose

/Free Fructose)

Requires no digestion and

are ready for absorption.
Monosaccharides are readily

absorbable forms from GIT

lumen.

Simple sugars require very

less time to reach blood and

cells.

Drinking Glucon?D give

instant energy in very few

minutes.

Digestion Of Disaccharides

Digestion of Disaccharides takes

place in small intestine.

Disaccharides are digested by specific

Disaccharidases.

Lactase, Maltase, Sucrase (Invertase)

and Isomaltase are specific

Disaccharidases.
Lactase cleaves (1-4)

glycosidic bond of Lactose

Maltase cleaves (1-4)

glycosidic bond of Maltose

Sucrase cleaves 1 2

glycosidic bond of Sucrose

Lactose Lactase Glucose + Galactose

Maltose Maltase Glucose + Glucose

Sucrose Sucrase Glucose + Fructose
Digestion Of Polysaccharides

Starch and Glycogen are

digested by enzyme Amylase.

Amylase is a Starch and

Glycogen digesting enzyme.

Types of Amylases

Salivary Amylase
(Mouth-Salivary Juice)
Pancreatic Amylase
(Small Intestine-Pancreatic Juice)

Amylase cleaves -(1-4) glycosidic

bonds of Starch , Dextrin and Glycogen.
Chloride ion is an

inorganic cofactor for

-Amylase activity.

Digestion of Starch and Glycogen

begins in mouth by the action of

salivary Amylase (pH- 6.6)

Digestion of Starch is incomplete

in mouth.

Dextrin is an intermediate of

Starch digestion.
Significant and complete

digestion of Starch occurs in

intestine by Pancreatic

Amylase(pH 7.1).

Maltose and Isomaltose are

end products of Starch

digestion by Amylase activity.

Maltose and Isomaltose are then

hydrolyzed by Maltase and

Isomaltase to liberate free Glucose

units.

Thus end product of Starch

digestion is many Glucose units.
No Digestion of Dietary Cellulose

Dietary Cellulose is not digested

in human GIT due to absence of

Cellulase digesting enzyme

Cellulose.

Cellulase in ruminants cleaves (1-

4) glycosidic bonds of Cellulose to

form Cellobiose.

Dietary Oligosaccharides

are not digested by GIT

enzymes.

Bacterial enzymes act upon it

to produce gas.

Thus Oligosaccharides of

diet apt to cause flatulence.
No Digestion Of Carbohydrates in

Stomach

Gastric juice of stomach has:

vNo specific Glycosidase for

Carbohydrate digestion.

vNo optimal pH for enzyme action.

Salivary Amylase of mouth carried to

stomach along with food bolus is

inhibited by vey low pH of gastric juice.

Monosaccharides

is an End Product Of

Carbohydrate Digestion.
End products of

Carbohydrate digestion are :

Monosaccharides- Glucose ( 80%)
Galactose
Fructose

Absorption Of Monosaccharides

Monosaccharides an end product

of Carbohydrate digestion are

absorbable forms.

Site of Absorption :

Small Intestine
vDuodenum
vUpper part of Jejunum
Relative Rates of Absorption

Coefficient /Relative rates of absorption of

different Monosaccharides in intestine:

Glucose= 100
Galactose = 110
Fructose = 43
Mannose = 20
Xylose = 15
Arabinose = 09

Modes of Absorption

Glucose and Galactose ? (Complete)
Active Transport mechanism
Fructose ?
Facilitated Diffusion
Pentose-
Simple Passive Diffusion.
Absorption Of Glucose

Glucose absorption by active

transport mechanism.

Sodium dependent Symport

Co-Transport type.

(Secondary Active Transport)

Glucose Transportation Requires:

Protein carrier molecule

Na + ions

Sodium-Potassium ATPase.

ATP


Glucose and Galactose are

absorbed by same Glucose

transporter.

Absorption of Glucose and

Galactose is complete since it

is by active transport

mechanism.


Absorbed Glucose ,Galactose

and Fructose simply diffuse in

blood capillaries and carried

from intestine to Liver by

Hepato Portal Circulation.

Thus Liver is the first station to

receive dietary Carbohydrates.
From Liver Carbohydrates

are then distributed to

remaining all tissues and

cells of human body through

systemic circulation of

blood.

Disorders

Of

Carbohydrate

Digestion

and

Absorption.
Lactose Intolerance

Lactose Intolerance

Dietary Lactose not

tolerated.

No digestion and

absorption of dietary

(Milk) Lactose.
Causes

Congenital / Acquired
Deficiency of Lactose

digesting enzyme

`Lactase'

Biochemical Alterations

Dietary Lactose not digested due

to deficient Lactase.

Lactose remains in GIT and is

acted upon by bacterial enzymes

to Lactic acid and Gas (H2,CO2,

Methane).
Lactic acid and Lactose are

washed out through fecal

excretion.

Loss of body water and

electrolytes through feces.

Water and Electrolyte

imbalance/Dehydration

(Mixed Type Dehydration)

Clinical Manifestations

Lactic acid excretion causes

irritant osmotic diarrhea.

Gas excretion causes flatulence.
Abdominal cramps.
Increased motility of intestine.
Weakness.
Confusion.
Diagnosis

Benedicts Test on stool

specimen .

Positive result of

Benedicts test confirms

diagnosis.

Management

Lactose intolerance is managed

by avoiding dietary intake of

foods (Milk and Milk Products)

containing Lactose.

Intake of Curds which contains

Lactobacillus.
Incidence and Prevalence

More than half of world

population is suffering from

Lactose Intolerance.

90 % Asians

(More in South India)
10 % Africans.

Glycaemic Index (GI) Of

Carbohydrate Foods.
Glycemic index (GI)

measures an increase in

post prandial(PP) blood

Glucose after ingestion of

dietary Carbohydrates.

GI of a food is calculated in

comparison with an

equivalent amount of Glucose

liberated by food such as

bread/boiled rice.
Glycaemic Index Of Common

Foods

Foods

Glycaemic Index

Potatoes, Corn Flakes

80-90

Whole Wheat Bread,

70-79

White Rice

Brown Rice, Bananas

60-69

Buck Wheat, Frozen Peas.

50-59

Peas, Beans

40-49

Legumes, Milk, Ice

< 40

cream, Peanuts.
Factors Affecting GI

Degree and pattern of rise in post

prandial Glycaemia depends on:

Amount of dietary Carbohydrate

ingested.

Type of dietary Carbohydrate ingested.
Extent of dietary Carbohydrate

digested and absorbed in GIT.

Steep rise of post prandial

Glucose is noted on ingestion

of refined sugars.

Refined free sugars enter the

blood and body pleasantly,

imperceptibly and effortlessly

within very less time.
Less steep rise of post prandial

Glucose is noted on ingestion of

dietary complex carbohydrates like

Starch/Cellulose.

Starchy food takes more time as

it takes effort to chew and less

palatable than refined and simple

sugar.

Factors Reducing Post Prandial

Glycaemia
Eating complex

Carbohydrates (Starch/

Glycogen).

Inadequate cooking of

Starch.

Inadequate chewing and

mastication of eaten food.

Eating non digestible

Carbohydrate Cellulose.

Eating large particle size of food.
Presence of Enzyme inhibitors in

food.

Presence of Protein or fat in

association with Carbohydrates.
Calorific value of sugar and

starch is same 4 Kcal/gm.

One who consumes sweets

and refined sugars get more

calories and prone to grow

over weight.

Importance to know GI of

Foods
Foods with high Glycaemic

Index (GI) increases the post

prandial glycaemia.

Foods with low GI decreases

the post prandial glycaemia.

Knowing the GI value of

food helps:

vIn planning a rational diet

for patients of Diabetes

mellitus.

vIn planning diet for persons to

gain and loose weight.
Uptake Of Glucose Within

The Cells

Absorbed Glucose is carried

from intestine through Hepato

portal circulation and reaches

the Liver.
Glucose is transported into the

cells with the help of specific

membrane bound Proteins

termed Glucose Transporters.

Glucose Transporters

Glucose Transporters (GluT) are

Transmembrane proteins present

in cell membranes

They help in uptake of Glucose from

blood into cells.
Glucose Transporters may be

Insulin dependent/Insulin

independent.

Types Of Glucose Transporters
GLUT-1 to GLUT-14 (Glucose

Transporter Isoforms) exist in the

membranes of various body cells.

These Glucose transporters

involved in Glucose uptake from

blood into specific tissues.


Type of GluT

Present on

Property

Organs

Glu T1

RBC `s, Brain, Retina, Insulin Independent

Placenta

GluT2

Liver, Intestinal cells Insulin Independent

GluT3

Neuron, Brain

Insulin Independent

GluT4

Skeletal Muscles,

Insulin Dependent

Heart, Adiposecytes

GluT5

Testis, Kidney,

Poor ability for

Sperms

Glucose and has good

uptake property for

Fructose.

GluT7

Liver Endoplasmic

Glucose transported

reticulum.

from E.R to cytosol.
Sodium Dependent Glucose

Transporter -1 (SGluT-1)

Present in membranes of intestinal

mucosal cells.

Helps in uptake of Glucose from

intestinal lumen to intestinal mucosal

cells.

Defect in SGluT-1 leads to Glucose

malabsorption.

Sodium Dependent

Glucose Transporter -2

(SGluT-2)

Present in kidney tubules
Defect in SGluT-2 leads to

Renal Glycosuria.
Inhibitors Of Glucose

Transport

Glycosides :

Phlorizin

(Inhibitor of Glucose Transporter-SGluT-1 of Intestine)
Ovabain

( Inhibitor of Na-K ATPase )

They reduces blood Glucose.

Therapeutically used to control blood Glucose in

Diabetes mellitus.
Locking Of Glucose Within The Cells

Free Glucose is permeable to cell

membrane.

Glucose entered in cells is

phosphorylated to Glucose-6-

Phosphate (Impermeable) and

locked within the cells.
Glucokinase in Liver

Glucokinase in presence of ATP

and Mg++ ions Phosphorylates

the Glucose to Glucose-6-

Phosphate when first enters the

hepatocytes.

The Glucokinase is specific for

Glucose

It has high Km value i.e low

affinity for Glucose for

phosphorylation reaction.
As Glucokinase is slow in action

not all Glucose molecules entered

in hepatocytes are

phosphorylated and locked.

The remained free form of Glucose

come out of Liver and carried

through Systemic circulation.

Thus Glucose from

systemic circulation

diffuses into extra hepatic

tissues.
Hexokinase In

Extrahepatocytes

The Glucose entered in extra

hepatocytes is phosphorylated to

Glucose-6-PO4 by an action of

Hexokinase in presence of ATP and

Mg ++ ions.

Hexokinase has low Km value

i.e very high affinity for Glucose

for phosphorylation reaction.

Glucose is readily locked by

Hexokinase in extra hepatocytes

at a very low Glucose

concentration.
Glucokinase

Hexokinase

Phosphorylates Glucose to Glu- Phosphorylates Glucose to Glu-6-

6-Po4 in hepatocytes.

Po4 in extra hepatocytes.

Glucokinase has high Km value Glucokinase has low Km value

Glucokinase acts when Glucose Hexokinase acts when Glucose

concentration is high(> 100

concentration is low.(< 100 mg%)

mg%)
Glucokinase is very specific

Hexokinase is not so specific acts

acts only on Glucose.

on Glucose ,Fructose and Mannose.

Glucokinase is dependent on

Hexokinase is not under influence

Insulin.

of Insulin.

Glucokinase is not inhibited

Hexokinase is inhibited by Glucose

by Glucose-6-PO4.

-6-PO4.
Glucose import


Metabolic Fates Of Glucose

Overview of Glucose Metabolism


Metabolic Pathways of Glucose

In Well Fed Condition
In well fed condition Under the influence

of Insulin.

Glucose-6-PO4 is metabolized as follows:

vFor Oxidation to produce chemical

form of energy ATP.

vFor Storing Glucose.(Glycogen and

TAG)

vFor production of Glucose derivatives

for metabolic use.

Complete Oxidation Of Glucose via (In all Cells)

Glycolysis/EMP pathway
PDH complex reaction
TCA Cycle/Krebs Cycle

Formation and Storage of Glycogen by

Glycogenesis (Liver and Muscles).

Alternative Glucose Oxidation

HMP Shunt (NADPH+ H+ and Ribose)
Uronic Acid Pathway (Glucoronic acid)
Glucose is transformed to :
Lipids( Lipogenesis)

? Fatty acids
? TAG
? Cholesterol

Proteins building blocks.

qNon essential Amino acids.

Precursor for Lipogenesis is Acetyl ?CoA.
Precursor for Amino acids is Pyruvate, OAA

Metabolic Pathways of Glucose

In Emergency Condition
In emergency fasting condition when

blood Glucose lowers under influence

of Glucagon body tries to regulate the

blood Glucose by stimulating:

Glycogenolysis
(Breakdown of Stored Glycogen)
Gluconeogenesis
(Biosynthesis of Glucose).
Pattern to Study A

Metabolic Pathway

? Synonyms/Different Names of Pathway.
? What is the Pathway ? (In brief)
? Where the pathway occurs?
(Organ/Cellular site)
? When pathway occurs?
(well fed/emergency/aerobic/anaerobic)
? What type Of Pathway?
(Catabolic/Anabolic)
? How the pathway Occurs? (Type of Rxn,

Enzymes ,Coenzymes)

? Why the Pathway occurred? (Significance)
? Precursor, intermediates, byproducts

and end products of Pathway.

? Energetics of the pathway
(If Catabolic Pathway)
? Interrelation ships with Other Pathways.
? Regulation of Pathway :Modes of

regulation.

? Regulatory hormone/ Regulatory

Enzyme/Modulators.

? Inborn Error of the Metabolic Pathway

Complete Oxidation Of Glucose
The main aim of Glucose in cells is to oxidize
(Remove Hydrogen) and catabolize to liberate energy.

Glucose (C6) is completely oxidized to free CO2, H2O and

Energy (ATP). Glucose is completely oxidized via:

Glycolysis
(1 Glucose 2 Pyruvate and ATP)
PDH Complex reaction
( 2Pyruvate 2 Acetyl-CoA and ATP)
TCA cycle
(2 Acetyl ?CoA CO2, H2O and ATP)

GLYCOLYSIS
Synonyms Of Glycolysis

Embden Meyerhof Parnas (EMP)

Pathway

Aerobic and Anerobic Oxidation Of

Glucose.

Oxidation Of Glucose to Pyruvate.
Conversion of Glucose to Lactate.
What is Glycolysis?

Major Oxidative Pathway of Glucose.
Takes place in cytosol of every cell of

human body.

Glucose undergoes series of significant

catabolic reactions in aerobic and

anaerobic conditions to form Pyruvate

and Lactate respectively.
Glucose(6C) 2Pyruvate + ATP

(Aerobic Glycolysis) (3C)

Glucose 2 Lactate +ATP

(Anaerobic Glycolysis) (3C)

Byproduct of Glycolysis is ATP.


Nature /Type Of Glycolysis

Pathway
Glycolysis is a catabolic/ degradative

pathway.

Oxidation of Glucose occurs in Glycolysis.
Removal of Hydrogen from Glucose

structure.

Temporary acceptor of removed Hydrogen

is coenzyme NAD+ which get transformed

to form reducing equivalent NADH+ H+.

Glycolysis-Energy Generating

Pathway

The NADH+ H+

generated in the steps

of Glycolysis enters

ETC for its reoxidation

and generation of ATP.
When Glycolysis Occurs?

Glycolysis Occurs In

Cells when it needs energy .
Aerobic/Anaerobic condition
(Uniqueness).
Well fed condition (Actively).
Erythrocytes needs continuous

and uninterrupted Glycolysis

for their survival.

Where Glycolysis Occurs?
Glycolysis

Occurs in

Cytoplasm of all

body cells.

How Glycolysis Occurs?


Glycolysis occurs in 10 steps.

Glycolysis is studied in
3 phases/3 stages:

Phase I- Energy Utilizing Phase
Phase II- Splitting Phase
Phase III- Energy Generating Phase




Enzyme Kinases
Involves ATP
Require Mg ++

ions as cofactors.


1. Phosphorylation Reaction
2. Isomerization Reaction
3. Phosphorylation Reaction
4. Lyase- Splitting Reaction
4 a. Isomerization Reaction.
5. Oxidation and Phosphorylation Reaction
6. Substrate Level Phosphorylation Reaction
7. Mutase Reaction
8. Dehydration Reaction
9. Substrate Level Phosphorylation Reaction


High Energy Compounds of

Glycolysis:

1,3 Bis Phospho Glycerate.
Phospho Enol Pyruvate.
These high energy compounds

have "high energy" bonds (~P) in

their structures.

Cleavage of these high energy

bonds releases high energy .

Which is used for phosphorylation

of ADP + pi and generation of ATP

at reaction/substrate level.

Thus a high energy

compound in a

catabolic pathway is

followed by a substrate

level Phosphorylation

reaction.
Substrate Level

Phosphorylation Reaction

Is a mode of generation of

ATP at substrate level after

the cleavage of high energy

bond present in a high energy

substrate.

Glycolysis has 2 Substrate

level phosphorylation

reactions.

This mode of generation

of ATP at reaction level is a

quick/immediate mode.
? 2Substrate Level Phosphorylating

Enzymes of Glycolysis :

?Phospho Glycerate Kinase
?Pyruvate Kinase

Glycolysis has

3 irreversible reactions(1,3 and 9)
(1 oxidation reaction)-2NADH+H+
2 high energy compounds.
2 substrate level phosphorylation

reactions. ( 4ATPs)
3 Irreversible Enzymes of Glycolysis

vGlucokinase (GK)
vPhospho Fructo Kinase (PFK)
vPyruvate Kinase (PK )

Byproducts/ Energetics Of

Glycolysis

Reduced Coenzymes 2(NADH+H+) 5ATP
(1 NADH + H+ E.T.C 2.5 ATP)

2 ATP's each from two substrate level

phosphorylation rxns.(4 ATP's).

9 ATP's ? 2 ATP's = 7 ATP's Net gain.
Enzyme Rxn Of Glycolysis

Number of ATP

Utilized/Generated

Aerobic

Anaerobic

Condition

Condition

Glucokinase/Hexokinase

- 1 ATP

- 1 ATP

Phosphofructokinase(PFK)

- 1 ATP

- 1ATP

Glyceraldehyde-3-PO4

2(NADH+H+ 2(NADH+H+

Dehydrogenase.

enter ETC= do not enter ETC=
+5 ATP)

0ATP)

Phosphoglycerate Kinase

+ 2ATP

+ 2 ATP

Pyruvate Kinase

+ 2ATP

+ 2 ATP

Net + 7ATP's.

Net + 2 ATP's.

1 Glucose with Aerobic

Glycolysis 7 ATP's.

1 Glucose with

Anaerobic Glycolysis

2 ATP's.
Intermediates and end products

of Glycolysis serve as a

precursors for biosynthesis :

Fatty acid

Cholesterol

Amino acid

Regulation Of Glycolysis

Hormones regulating Glycolysis:
INSULIN- Stimulates Glycolysis
(Well fed Condition)
GLUCAGON ? Inhibist Glycolysis
(Emergency Condition)
Regulatory / Key Enzymes of Glycolysis :

3 Irreversible step catalyzing Enzymes:

v Glucokinase/Hexokinase
vPhospho Fructo Kinase ( PFK1) (IMP)
vPyruvate Kinase ( PK )

Insulin and Glucagon

stimulate and inhibit

Key/Regulatory

enzymes of Glycolysis

respectively.
Al osteric Activators of PFK

AMP
Fructose-2,6 Bis Phosphate
( Produced by PFK2 activity)
NAD+
Pi ( Inorganic Phosphorous )

Al osteric Inhibitors Of PFK

ATP
Citrate
NADH+ H+
H + ions ( Low pH /Acidosis)
Feed Forward Regulation

Pyruvate Kinase is activated

by Fructose-1,6 bisphosphate

formed by PFK1 activity.

This stimulates Glycolysis

actively.

Inhibitors of Glycolysis

Fluoride Inhibits Enzyme

Enolase of Glycolysis.

Arsenite ,Iodoacetate Inhibits

Glyceraldehyde-3-PO4

Dehydrogenase.
Significance Of Glycolysis:

Glycolysis is an unique pathway

operated in cytosol of each and

every cell to generate chemical

form of energy

7 ATP (Aerobic Condition)
2 ATP (Anaerobic condition).

In Aerobic conditions Glycolysis

provides energy (ATP) analogous to

Cheque
(NADH+H+ enters Oxidative

phosphorylation /ETC) and

Cash
(Substrate level Phosphorylation).
Intermediates of Glycolysis may serve

as precursor for non essential amino

acids.

Pyruvate Transaminase Alanine

Fates Of Pyruvate

In Aerobic

and

Anaerobic Conditions
Pyruvate (3C )

keto acid is an end

product of

Glycolysis.

Fate Of Pyruvate In Aerobic

condition:

Pyruvate is oxidatively decarboxylated

to Acetyl-CoA (2C) by the activity of

Pyruvate Dehydrogenase (PDH)

complex.

A reducing equivalent NADH+H+ is

released at this reaction.
Fate of Pyruvate in Anaerobic

Condition:

Pyruvate is reduced to Lactate by the

activity of Lactate Dehydrogenase

(LDH) .

NADH +H+ generated in Glycolysis and

not entering in ETC, in anaerobic

condition is utilized in the reduction

of Pyruvate to Lactate.

Lactate is said

to be the dead

end Of the

Glycolysis.
Significance of Pyruvate Reduction

To Lactate

Utilizes the Glycolytic generated

NADH+H.

Does not accumulate the NADH+H+

to inhibit PFK of Glycolysis.

Avoid interruption of Glycolysis and

continue it in anaerobic condition.

Physiologically during

strenuous exercise.

Muscle lacks enough oxygen.
Anaerobic Glycolysis forms

major source of energy to

exercising muscles.
Lactate serves as a fuel source for

cardiac muscle as well as brain

neurons .

Astrocytes, which surround and

protect neurons in the brain, ferment

Glucose to Lactate and release it.

Lactate taken up by adjacent neurons

is converted to Pyruvate that is

oxidized via Krebs Cycle.

Lactic acidosis is

noted when there is

collapse in

circulatory system.
Tissues in hypoxic condition

produces Lactate.

For ex in Ischemia, MI,

Embolism , Shock.

Lactate causes fatigueness of

muscles.

Lacticacidosis is a

condition of Metabolic

Acidosis where the

blood pH is lowered.
Lacticacidosis detects Oxygen

Deficiency

Oxygen debt leads to interrupt

Glycolysis.

Anaerobic Glycolysis.
Low/No production of ATP.
Lacticacidosis.

Oxygen debt is related to patients

morbidity or mortality.

Measuring Lactate levels of blood

allows rapid and early detection of

oxygen debt.

Correction of early Oxygen debt

helps in recovering the patients life.


Inborn Error Of Glycolysis
Pyruvate Kinase

deficiency in

Erythrocytes leads to

Hemolytic Anemia

(Nonspherocytic

Hemolytic Anemia).

PK deficiency

interrupts Glycolysis.

Interrupted Glycolysis

affects the RBC's and

leads to its lysis.
Glycolysis in Cancer

In fast growing cancer cells Glycolysis

proceeds at a high rate forming large

amounts of Pyruvate.

This Pyruvate is then reduced to

Lactate.

This produces relatively acidic local

environment in tumor.

Rapaport Leubering Cycle
Synonyms

2,3 Bis Phospho Glycerate

Cycle /(2,3BPG Cycle)

Shunt Glycolysis In

Erythrocytes

Location/ Occurrence :

15-25% of Glucose

enter via 2,3 BPG cycle

in the cytosol of

mature Erythrocytes.


End Product of

Glycolysis in

Erythrocytes is

Lactate.
Mature Erythrocytes has no

Mitochondria.

Pyruvate obtained from

Glycolysis could not be further

oxidized in Erythrocytes.

Pyruvate is reduced to Lactate

by LDH in Erythrocytes.

Salient Features Of

Rapaport Leubering Cycle
In Rapaport Leubering cycle
A high energy compound 1,3 Bis

Phospho Glycerate is

transformed to a low energy

compound 2,3 Bis Phospho

Glycerate.

2,3 Bis Phospho Glycerate is

dephosphorylated to 3 Phospho

Glycerate and utilized.

This bypasses the substrate

level phosphorylation of

Glycolysis
Rapaport Leubering Cycle

generates no ATP.

It dissipiates/waste energy

as heat.

It does not accumulate

ATP

Energetics Of Glycolysis In RBC's
Erythrocyte Glycolysis via 1,3 BPG



2 ATP

Erythrocyte Glycolysis via 2,3 BPG

O ATP

Significance Of

Rapaport Leubering Cycle
Rapaport Leubering Cycle

Maintains Glycolysis in

continuous and uninterrupted

in RBC's.

This in turn maintains cellular

integrity of RBC's.

Prevent hemolysis.

2,3BPG of Rapaport

Leubering cycle in RBC's:

Has high affinity for

Hemoglobin.

Helps in unloading of

Oxygen by OxyHb at tissues.
2,3BPG Increases In

? Hypoxic conditions

?High altitudes
?Fetal tissue
?Anemic Condition

Inborn Error Of

Rapaport Leubering Cycle
Hexokinase Pyruvate Kinase

Deficiency

Deficiency

Decreases 2,3 BPG Increases 2,3 BPG

concentrations.

concentrations.

Decreases

Increases

Unloading of

Unloading of

Oxygen at tissues. Oxygen at tissues.

Pyruvate Metabolism

OR

Formation and Fates Of Pyruvate


GLUCOSE

MALATE

ALAN



INE







PYRUVATE



OXALOACETATE

ACETYL-CoA

LACTATE
PYRUVATE IS FORMED FROM

Glucose (Glycolysis)
Lactate (Oxidation-LDH)
Malate (Malic enzyme)
Alanine (Transamination-ALT)

PVRUVATE IS CONVERTED TO

Glucose (Gluconeogenesis)
Lactate (Reduction-LDH)
Malate (Malic enzyme)
Alanine (Transamination-ALT)
Acetyl-CoA ( PDH Complex)
Oxaloacetate (Carboxylation

Rxn)
Pyruvate Irreversibly forms

Acetyl-CoA

Oxaloacetate

In Mitochondrial Matrix
These are the precursors

of TCA cycle.

Oxidative Decarboxylation

Of

Pyruvate To Acetyl-CoA

By

Pyruvate Dehydrogenase (PDH)

Complex.
GLUCOSE

TCA

CYCLE

Glycolysis

NADH+H+

CO2

NAD+

PYRUVATE

Acetyl-

CoA

PDH

Complex

Pyruvate is generated as an end

product of Glycolysis in the

cytoplasm.

This is then transported into

Mitochondrial matrix

By a Pyruvate transporter

located in the mitochondrial

membrane.
Pyruvate, a 3 carbon keto acid
Obtained from Glycolysis is

oxidized (removal of Hydrogen)

and decarboxylated (removal of

CO2)

To form a 2 carbon, high energy

compound Acetyl-CoA and

Reducing equivalent NADH+ H+.

Reducing equivalents

NADH+H+ released at this

step enter in E.T.C for it's

reoxidation and generation

of ATP's.

Thus this is an energy

producing step.
Oxidative

Decarboxylation of

Pyruvate to Acetyl-CoA

Is biocatalyzed by PDH

complex(Multi Enzyme

Complex).

Acetyl-CoA formed

in PDH complex step,

enters in TCA cycle

for its complete

oxidation.
Thus PDH complex reaction

is a connecting reaction

between Glycolysis and TCA

cycle.

PDH Complex

Neuberg (1911) discovered PDH

complex.

PDH Complex is a Multi Enzyme

complex.

PDH complex is composed of:
3 Enzymes and 5 Coenzymes.
Three Enzymes Of PDH Complex:

vPyruvate Dehydrogenase
vDi Hydrolipoyl Dehydrogenase
vDi Hydrolipoyl Transacetylase

? Five Coenzymes Of PDH Complex.

?TPP (Derived from Vit B1)
?FAD (Derived from Vit B2)
?NAD+ (Derived from Vit B3)
?CoA-SH (Derived from Vit B5)
?Lipoic acid/Lipoamide.
Associated Enzymes and Coenzymes Of PDH

Complex:

Pyruvate Dehydrogenase (E1)

(Coenzyme = TPP)

Dihydrolipoamide Acetyltransferase (E2)

(Coenzymes = Lipoamide, CoA)

Dihydrolipoamide Dehydrogenase (E3)

(Coenzymes = FAD, NAD+)

Location Of PDH complex:

PDH complex is

located in

Mitochondrial matrix.
Reaction biocatalyzed by

PDH Complex is

completely an irreversible

reaction.

Due to irreversible nature of PDH

complex reaction:

Acetyl-coA obtained through
oxidation of Fatty acids

cannot be converted to Pyruvate

and used for Glucose production.

Thus Fat is not converted to

Carbohydrates in human body.
Working Of PDH Complex

PDH Complex irreversibly

biocatalyzes

An Oxidative Decarboxylation

of Pyruvate to Acetyl-coA

At aerobic conditions in

mitochondrial matrix.



Regulation Of PDH Complex

PDH Complex is

stimulated by INSULIN.

PDH Complex is inhibited

by GLUCAGON.

Activators Of PDH Complex.

ADP
NAD+
Inhibitors Of PDH Complex

ATP
NADH+ H+
Cyclic AMP
Acetyl-CoA

Chemical Inhibitors Of PDH

Complex

Arsenic
Mercuric Ions
Deficiency Of

PDH Complex

And Its

Consequences

PDH Complex deficiency is rare
It blocks the conversion of Pyruvate to

Acetyl-CoA

Brings incomplete Oxidation Of Glucose
Increases Pyruvate concentration
Increased Pyruvate is reduced to Lactate
Leads to Lactic acidosis
Decreases Acetyl ?CoA, which Decreases TCA

cycle

Decreases ATP level
Low ATP levels affects cellular activities.
Fatigue ,Weakness, Neurological Disorders.
TCA CYCLE

Synonyms OF TCA Cycle
Fate of Acetyl CoA
Tri Carboxylic Acid Cycle (TCA Cycle)
Citric Acid Cycle
Krebs Cycle (Hans Kreb-1937)
Amphibolic Pathway
Common Metabolic Pathway
Central Metabolic Pathway
Final Oxidative Pathway

What Is TCA Cycle?
Common metabolite Acetyl-CoA
Obtained from Glucose, Fatty

acids and Amino acid metabolism

Finally , commonly and

completely oxidized via TCA cycle.

1 Acetyl-CoA +3NAD+ + FAD + GDP + Pi

Over all TCA

2 CO2+CoA + 3NADH +3H++ 1FADH2 + 1GTP
Acetyl-CoA a central/common

metabolite is completely oxidized

To liberate 2CO2, and reducing

equivalents 3NADH+H+ , 1 FADH2

and 1GTP through TCA cycle.



10 ATPs generated on

oxidation of

1 Acetyl CoA via TCA

cycle
Nature/Type Of Pathway

TCA is an Amphibolic

Pathway.

It is connected to both

Amphibolic and

Catabolic Pathway.
Condition In which Pathway Occurs

TCA is purely

carried out in an

Aerobic condition.
Location : Organ and Cellular Site

TCA is carried out in all

cells which contain

Mitochondria.

Cellular site for TCA is

Mitochondrial Matrix.
TCA cycle des not

operate in

Mature Erythrocytes

,Cornea and Lens cells

Since they are devoid of

Mitochondria.

Reactions Steps OF TCA Cycle:
TCA cycle

constitutes 10 steps.

Acteyl?CoA and

Oxaloacetate(OAA)

are initators of

TCA cycle.
Sources Of Acetyl CoA

Glucose Metabolism
(PDH Complex Reaction)
Fatty Acid Metabolism
( Oxidation of Fatty acids)
Amino Acid Metabolism

Sources Of Oxaloacetate(OAA)
OAA used in TCA is majorly

obtained from Glucose

metabolism

(In a well fed condition )
OAA comes minorly from

Amino acid (ASP)

[In an emergency condition].

Oxaloacetate is a 4 Carbon Keto acid

obtained from Pyruvate a 3 Carbon Keto

acid on Carboxylation reaction.

Pyruvate is carboxylated to Oxaloactate

by an irreversible activity of an enzyme

Pyruvate Carboxylase, ATP and

Coenzyme Biotin.


In TCA cycle Oxaloacetate used

up in first step is regenerated in

last step.

2 carbon units lost in TCA cycle in

the form of CO2 is from OAA .

The regenerated OAA gets 2

Carbon atoms from entered 2

carbon Acetyl-CoA.
TCA Is An Amphibolic Pathway

Catabolic Role Of TCA Cycle


TCA is associated to Carbohydrates

,Lipids, and Proteins for its complete

metabolism.

65-70% of ATP is generated through

TCA cycle.

TCA is a most energetic metabolic

pathway.


1. Aldol Condensation
2. Isomerization- Dehydration and Rehydration
3. Oxidation
4. Decarboxylation
5. Oxidative Decarboxylation
6. Substrate Level Phosphorylation
7. Oxidation
8. Hydration
9. Oxidation
Central metabolite Acetyl-CoA obtained

from Glucose, Fatty acids, and Amino acid

metabolism.

Acetyl-CoA enters in TCA cycle and

completely oxidized to free CO2 and

reducing equivalents which further enters

ETC to generate ATPs.

Since Acetyl-CoA is catabolized and

produces energy.

Thus TCA has catabolic and energy

generating role.

Succinate Dehydrogenase is the

only enzyme of TCA embedded in

the inner mitochondrial

membrane.

Succinate Dehydrogenase

functions as Complex II of ETC.
Alpha KDH Complex Is a

Multi Enzyme Complex

3 Enzymes

Alpha Keto Glutarate

Dehydrogenase

Dihydrolipoyl

Dehydrogenase

Dihydrolipoyl Trans

Succinylase
5 Coenzymes

TPP
FAD
NAD+
Lipoamide
CoA

Anabolic Role Of TCA


Citric acid cycle intermediates are

always in flux

In TCA Cycle there is

continuous influx and efflux of

intermediate metabolites as per

cellular need.

TCA is considered as a

metabolic Traffic Circle.
Various intermediates of TCA

cycle are connected to the

biosynthesis of various

functional biomolecules of

human body.

This role of TCA signifies

Anabolic role .

Citrate a 6 carbon moiety is a

first Tricarboxylic acid

produced in TCA.

Citrate is a carrier of acetate

carbons for De novo

biosynthesis of Fatty acids in

cytosol.
Acetyl CoA obtained

from Glucose in a well

fed condition is a

precursor of fatty acid

biosynthesis.

Acetyl ?CoA is impermeable

to mitochondrial membrane.

Impermeable Acetyl-CoA of

mitochondria is brought out in

the cytosol in a permeable

form of Citrate.
Citrate in cytosol

undergo lysis by Citrate

Lyase to regenerate

Acetyl-CoA and OAA.

Alpha Keto Glutarate ( KG) a 5

carbon Keto acid, an intermediate

of TCA is involved in

Transamination reaction of

Aminoacids.

KG is an acceptor of an amino

group from another amino acid

involved in Transamination

reaction.
KG on Transamination forms its

corresponding amino acid

Glutamic acid.

Thus KG is a precursor for

biosynthesis of non essential

amino acid in human body.

Oxaloacetate of TCA is also

transaminated to a non essential

amino acid Aspartate.

Intermediates of TCA are

Glucogenic precursors

In an emergency conditions they

are used for biosynthesis of

Glucose.
Succinyl ?CoA, a high energy

compound ,an intermediate of TCA

cycle is followed by Substrate level

Phosphorylation reaction to generate

GTP at reaction level.

Succinyl-CoA is a precursor for Heme

biosynthesis .

Succinyl-CoA is involved in Ketolysis

where it is a CoA donor for

Thiophorase reaction.

Intermediates of TCA cycle are

connected to Biosynthesis of

Lipids
(Lipogenesis )
Glucose
(Gluconeogenesis)
Aminoacids
(Nutritionally Nonessential)
TCA cycle is termed as

open cycle- Since an

intermediates of TCA

cycle enter and leave the

cycle as per the cellular

need.

TCA Cycle is analogus/

Illustrated as- "Heavy Traffic

Circle" in a National

Highway with many

connecting roads.

Since many intermediates of

TCA cycle are interconnected

to other metabolic pathways.
TCA Cycle provides

intermediates for many

biosynthetic processes

Energetics Of Per Turn TCA Cycle
Enzymes Generating Reducing

Equivalents

Isocitrate Dehydrogenase -------------NADH+H+

Ketoglutarate Dehydrogenase -------NADH+H+

Malate Dehydrogenase------------------NADH+H+

Succinate Dehydrogenase --------------FADH2

Succinate Thiokinase --------------------GTP

In per turn of TCA cycle 1 Acetyl-

CoA enters to catabolize and

generate 3NADH+ H+ 1 FADH2

and 1 GTP.
3 NADH+ H+ when enters ETC it generates

7.5 ATPs

1 FADH2 when enters ETC generates 1.5

ATPs.

1 Substrate level phosphorylation generates

1 GTP.

Net 10 ATP's are generated per turn of TCA

cycle.

Significance of TCA

TCA Cycle is the

largest generator of

ATP among the

metabolic pathways.
Reduced Coenzymes Fuel ATP

Production

Isocitrate Dehydrogenase

1 NADH=2.5

ATP

a- Ketoglutarate Dehydrogenase

1 NADH=2.5

ATP

Succinate Thiokinase

1 GTP=1 ATP

Succinate Dehydrogenase

1 FADH2=1.5 ATP

Malate Dehydrogenase

1 NADH=2.5

ATP

Total of 10 ATPs gained from oxidation of 1

Acetyl-CoA per TCA turn.

GTP formed in TCA cycle is

used in following step of

Gluconeogenesis:

Conversion of Oxaloacetate

to PhosphoenolPyruvate

(PEP) in presence of enzyme

PEP Carboxykinase and GTP.
Regulation Of TCA Cycle

Hormone Insulin in well fed condition

stimulates and activates key / regulatory

Enzymes of TCA cycle.

Key Enzymes of TCA cycle :
Citrate Synthase
Isocitrate Dehydrogenase (IDH)
Keto Glutarate Dehydrogenase

(KDH)

Activators of key Enzymes-

ADP,AMP

Inhibitors Of key Enzymes-

ATP, NADH+ H+, Succinyl-CoA
Citrate of TCA inhibits PFK of

Glycolysis.

Citrate stimulate Fructose -1,6

Bisphosphatase of

Gluconeogenesis.

Citrate activates Acetyl CoA

Carboxylase of Fatty acid

biosynthesis.

Regulation Of TCA by availability of ADP:

Low levels of ADP in cells indirectly inhibit

TCA cycle.

ADP is required for synthesis of ATP through

oxidative phosphorylation (ETC).

Low/Limited ADP are insufficient to reoxidize

reducing equivalents NADH+ H+ ,FADH2

generated during TCA.

This accumulates NADH+ H+ ,FADH2 which

are inhibitors of key enzymes of TCA cycle.
Chemical Inhibitors OF TCA cycle

INHIBITOR

ENZYME INHIBITED

and Type
Fluoroacetate Aconitase

(Non Competitive)
Arsenite

Keto Glutarate

(Non Competitive) Dehydrogenase.

Malonate

Succinate

(Competitive)

Dehydrogenase

TCA enzyme defects

has reported to suffer

from severe

neurological damage

due to impaired ATP

formation in CNS.
Hyperammonaemia Impairs TCA

High ammonia levels in blood are

toxic to body since they deplete

the levels of -Keto Glutarate.

(an intermediate of TCA cycle)
Low levels -Keto Glutarate, affects

the operation of TCA cycle and

production of ATPs.

Vitamin B Complex deficiencies affects

Glucose metabolism and has low ATP

production.

Vitamin B complex members are

modified to Coenzymes required in

enzyme catalysis of metabolic reactions.

One should take care to supplement

adequate Vitamin B complex through

ingestion of fresh fruits and vegetables.
Beri Beri and
Wernicke Korsakoff Syndome ( In

alcoholics)

Due to Thiamine (TPP) deficiency.
TPP is a member of multienzyme

complex PDH and Alpha KDH.

Low TPP= low ATP
Low Nervous tissue , Cardiac Functions.

Pellegra is due to Niacin deficiency.
Niacin deficiency affects the

concentration of coenzymes NAD+

and NADP.

NAD+ and NADP deficiency affects

metabolism by low ATP

production.
Leigh Syndrome

Leigh Syndrome is a rare disorder
Also referred as Sub acute Necrotizing

Encephalomyelopathy

Progressive neurological disorder
Defect in mitochondrial ATP production
Mutations in PDH Complex/ATP Synthase of

ETC.

Anaplerotic Reactions/

Anaplerosis
Anabolic reactions connected

to TCA cycle utilizes the

intermediates of this cycle.

The drawn up intermediates

should be replenished.

If not replenished ,TCA cycle

will stop to operate.

The biochemical

reactions which replenish

or add up/fill up the

intermediates of TCA

cycle and maintain its

operation are termed as

anaplerotic reactions.
The Anaplerotic Reactions

The "filling up" reactions

? PEP Carboxylase - converts PEP

to Oxaloacetate

? Pyruvate Carboxylase - converts

Pyruvate to Oxaloacetate

? Malic enzyme converts Pyruvate

into Malate

Anaplerotic Reactions

Pyruvate Pyruvate Carboxylase Oxaloacetate
CO2 ATP ADP Biotin

Pyruvate Malic Enzyme Malate
NADP NADPH+H+

Glutamate

GDH

Keto Glutarate

Aspartate AST Oxaloacetate
Energetics Of Complete Oxidation

of Glucose


1 molecule of

Glucose on

complete oxidation

in body cells

liberate 32 ATP's.
Glycogen Metabolism

Glycogenesis

And

Glycogenolysis
GLYCOGENESIS

GLYCOGENOLYSIS

Glycogenesis is biosynthesis Glycogenolysis is

of Glycogen from free and

breakdown of Glycogen to

excess of Glucose in well fed Glucose in emergency

condition in the cytoplasm condition in the Liver and

of Liver and Muscles.

Muscles.

Glycogenesis is an anabolic Glycogenolysis is a catabolic

process to store free excess degradative process to

Glucose in the form of

utilize the stored Glycogen

condensed , compact,

after its cleavage to release

globular, and granular form Glucose ,which on further

as ?Glycogen.

oxidation generate ATPs in

emergency conditions.

Where Glycogen Metabolism

Occurs?
Site/Location Of Glycogen

Metabolism

Organs for Glycogen Metabolism:

Liver and Muscles.
Cellular Site :

Cytoplasm

In Liver

Rate of Glycogen Synthesis- 6-8%
Amount Stored- 75-150 gm.

In Muscles

Rate of Glycogen Synthesis- 1-2 %
Amount Stored- 250-400 gm.
1% of Glycogen

stored in

cardiac/heart

muscles.

Storage of

Glycogen in

tissues is limited.
When Glycogenesis Operated?

Glycogenesis takes place after a

well fed condition.

After a heavy Carbohydrate

meals.

When there is free and excess

of cellular Glucose.

Under the influence of Insulin.
How Glycogenesis Occur?

Steps Of Glycogenesis


Process of

Glycogenesis

involves

following Steps:
Activation of

Glucose to

UDP-Glucose.
(Energetic Compound)

Glycogen synthesis

depends on sugar

nucleotides

UDP-Glucose
Glycogenesis Needs

Glycogen Primer

A Glycogen Primer

is required to

initate the process

of Glycogenesis
Glycogen Primer

at a very first time

of Glycogenesis in

a body is a Protein

Glycogenin.

Glycogenin

catalyzes primer

formation.
Glycogenin is a protein

scaffold on which Glycogen

molecule is built.

? First Glucose is linked to a

Tyrosine ?OH of Glycogenin.

Glycogenin by

auto glucosylation

using UDP-Glucose

form a Glycogen

primer.
Glycogen primer in

an adult body:

Is a residual of

Glycogen molecule left

out after

Glycogenolysis in

tissues.

Glycogen Synthase

? Glycogen Synthase is the main

enzyme of Glycogenesis.

? It forms -(1 4) glycosidic bonds in

Glycogen.

? Glycogen Synthase requires 4 to 8

Glucose units on Glycogenin for its

activity.
UDP- Glucose is linked

to non reducing ends of

Glycogen Primer by

Glycogen Synthase

activity to grow the linear

chain.

Glycogen Synthase

transfers Glucosyl units

from UDP-Glucose to C-4

hydroxyl at a nonreducing

end of a Glycogen

strand/Glycogen primer.
After stipulated

growth of linear chain,

Branching enzyme

adds a branching

point.

Alternate activities of

Glycogen Synthase and

Branching Enzyme occurs

To link UDP-Glucose units to

form a complex, compact and

condensed structure of

Glycogen.


During Glycogenesis.

Glycogen Synthase -builds (1-4)

glycosidic bonds.

Branching Enzyme ? Glucosyl
(4-6) Transferase builds (1-6)

glycosidic bonds.
More branching points in a

Glycogen molecule

Increases the number of non

reducing ends

Which can be elongated by

addition of new Glucose residues to

it

By Glycogen Synthase activity.

UDP released during

Glycogenesis is

converted to UTP at

an expense of ATP.
Significance Of Glycogenesis

Glycogenesis stores free

and excess Glucose in

condensed, compact and

granular form which:

Reduces osmotic effect
Occupy less space.
Glycogenolysis

Site Of Glycogenolysis

Cytoplasm of Liver and

Muscles.

Where Granules of

Glycogen stored.
When Glycogenolysis Occur?

Glycogenolysis occur in the body

when:

Stored Glycogen needs to be

utilized.

Blood or cellular Glucose lowers.
There is fasting or starvation.
There are long hours between

meals.
Steps Of Glycogenolysis

Glycogenolysis is not a

just reversal of

Glycogenesis.

A different sets of

enzyme used.


Glycogenolysis involves

cleavage of (1-4) and (1-6)

glycosidic bonds of Glycogen.

Enzyme Glycogen

Phosphorylase cleaves (1-4)

glycosidic bonds.

Debranching Enzymes

removes (1-6) glycosidic bonds.
? Glycogen Phosphorylase is a

main enzyme of

Glycogenolysis.

? Glycogen Phosphorylase

cleaves Glycogen at non-

reducing end to generate

Glucose-1-phosphate

? Glycogen Phosphorylase cleaves (1

-4) glycosidic bonds linking

Glucose from the non reducing

ends of glycogen molecules

? This is a Phosphorolysis, not a

hydrolysis

? Metabolic advantage: product is a

sugar-P - a "sort-of" Glycolysis

substrate


End Products Of Glycogenolysis
During Glycogenolysis

Enzyme Glycogen

Phosphorylase by its

activity releases

Glucose -1-PO4.

Debranching by

bifunctional (two) Enzymes.

Glucosyl (4 , 4) Transferase.
Amylo (1-6) Glucosidase
Debranching Enzyme

Amylo (1-6) Glucosidase

Acts on exposed

branching point (1-6)bond

of Glycogen and releases

free Glucose.

The number of free Glucose

units released during

Glycogenolysis depends upon

The number of branching

points hydrolyzed by

Debranching enzyme activity.
Glucose-1-PO4 : Free Glucose

8: 1

Released during Glycogenolysis

Muscle Glycogenolysis Liver Glycogenolysis
In Muscles Enzyme Glucose- In Liver Enzyme Glucose-6-

6-Phosphatase is naturally Phosphatase is naturally

absent.

present.

Glucose-6-PO4 ends as an

In Liver Glucose-6-PO4 of

end product of

Glycogenolysis is

Glycogenolysis which further transformed to free Glucose

enters Glycolysis and get

(permeable) by Glucose-6-

metabolized within muscle

Phosphatase activity.

cells.

Muscle Glycogenolysis has

Free Glucose formed from

no role in blood Glucose

Liver Glycogenolysis comes

regulation

out in blood and helps in

blood Glucose regulation.
Significance Of Glycogenolysis

Muscle Glycogen is

extensively degraded in

exercising muscles to

provide energy for it's

activity.
Liver Glycogenolysis operates to
Generate free Glucose from breakdown of

stored Glycogen.

Liver Glycogenolysis add free Glucose to blood.
Regulates blood glucose levels.
Correct fasting Hypoglycemia
Supply sufficient Glucose to Brain and

Erythrocytes.

Try to maintain good function of brain and

RBC's in fasting condition

Stored Glycogen in

Liver on Glycogenolysis

,supply Glucose in a

rapid and mobilizable

form.
Liver Glycogenolysis

regulates blood

Glucose levels in

early stages of fast.

Liver

Glycogenolysis

corrects fasting

Hypoglycemia.
Regulation OF

Glycogen Metabolism

Regulation means good coordination of

Glycogenesis and Glycogenolysis as an

when required by the body to maintain

blood Glucose in normal range.

Glycogen metabolism is regulated by

stimulation or inhibition of

regulatory/key enzymes of Glycogen

metabolism under hormonal influence.
Glycogenesis and

Glycogenolysis are

reciprocally regulated

In well fed condition

Glycogenesis is onn
Glycogenolysis is off

In fasting condition

Glycogenolysis is onn
Glycogenesis is off
Modes Of Regulation

Hormonal Regulation
(Covalent Modification Of Key Enzymes

of Glycogen Metabolism)

Allosteric regulation
Influence Of Calcium on

Glycogen Metabolism.

Hormonal Regulation

Insulin In well fed condition

Stimulates Glycogenesis
Inhibits Glycogenolysis
Glucagon and Epinephrine In

emergency condition :

Stimulates Glycogenolysis
Inhibits Glycogenesis

Glucagon and Epinephrine
Acts via second messenger

cyclic AMP by cascade of

reactions

Regulates the enzymes and

pathway of Glycogen

metabolism.
Glucagon has no effect

on Muscle Glycogenolysis.

Epinephrine and Calcium

stimulates Muscle

Glycogenolysis.

Regulatory Enzyme Of Glycogenesis:

Glycogen Synthase

Regulatory Enzyme Of Glycogenolysis:

Glycogen Phosphorylase.


Covalent Modification Of Enzymes

Glycogen

Glycogen

Phosphorylase

Synthase

v "A" Form Active Form

"A" Form Active Form

Phosphorylated Form

Dephosphorylated Form

v"B" Form Inactive Form

"B" Form Inactive Form

Dephosphorylated Form

Phosphorylated Form




Effect of glucagon and epinephrine on glycogen

phosphorylase glycogen synthase activities


Effect of Insulin on Glycogen Phosphorylase

Glycogen Synthase activities


Influence of Calcium in Regulation

of Glycogen metabolism.
Calcium stimulates Liver

and muscle Glycogenolysis

Calcium inhibits Liver and

muscle Glycogenesis.

Calcium binds to

Calmodulin, which then

activates an enzyme muscle

Phosphorylase Kinase b

and Liver Phosphorylase

Kinase b.
Calcium activated

Phosphorylase Kinase

b stimulates and

activates Glycogen

Phosphorylase.

Thus Calcium indirectly

activates Glycogen

Phosphorylase

Calcium Stimulates

Glycogenolysis.


Glycogen Storage Disorders

OR

Inborn Errors Of Glycogen

Metabolism
Glycogen Storage Disorders

are inherited/congenital

metabolic defects concerned

with Glycogenesis and

Glycogenolysis.

Cause:
Enzyme defects of Glycogen

metabolism.

Type:
Generalized/Tissue specific
Consequences of Glycogen Storage

Disorders:

Abnormal form or amount of

Glycogen is deposited in Muscles ,Liver

or both.

Affects the functional activities of

these tissues.

No correction of fasting hypoglycemia.
No supply of energy to muscles during

emergency conditions.

Types Of Glycogen Storage

Disorders
Type of Glycogen Name of Glycogen

Enzyme Defect

Storage Disorder

Storage Disorder

Type I

Von Gierke's Disease

Liver Glucose-6-

Phosphatase

Type II

Pompe's Disease

Lysosomal (1-4)

Glucosidase

Type III

Cori's Disease

Debranching Enzyme

Type IV

Anderson's Disease

Branching Enzyme

Type V

Macrdle's Disease

Muscle Glycogen

Phosphorylase

Type VI

Her's Disease

Hepatic Glycogen

Phosphorylase

Lewi's Disease

Glycogen Synthase

Type VII

Tauri's Disease

Phospho Fructo

Kinase

Disorders Related to Glycogenesis
Lewis Disease Glycogen Synthase

Deficiency

Andersons

Branching Enzyme

Disease

Glucosyl (4-6)

Transferase

deficiency.

Disorders Related to Glycogenolysis


Von Gierkes Disease

Enzyme Defect:

qLiver Glucose-6-Phosphatase deficiency

Biochemical Alterations and Manifestations:

vHypoglycemia
vHyperlipidemia
vHyperuricemia
vLacticacidemia
vMental retardation
vConvulsions
Pompe's Disease

Enzyme Defect:
Lysosomal (1-4) Glucosidase/Acid Maltase

Biochemical Alterations and Manifestations:

vGlycogen accumulates in Lysosomes of skeletal

and cardiac muscles and affect its function.

vCardiomegaly
vCongestive Heart Failure
vWeakness of respiratory muscles.

Cori's Disease (Limit Dextrinosis)

Enzyme Defect:

Debranching Enzyme Amylo (1-6)

Glucosidase deficiency.

Limit Dextrin gets deposited in Liver

and Muscles.
Macrdle's Disease

Enzyme Defect:
Muscle Glycogen Phosphorylase deficiency.

Biochemical alterations and manifestations:

No Glycogenolysis in muscles.
Abnormal Glycogen storage in muscles.
Excersise Intolerance.
Muscle cramps
Myoglobinuria.

Her's Disease

Enzyme Defect:
Hepatic Glycogen Phosphorylase deficiency.

Biochemical alterations and manifestations:

No Glycogenolysis in liver.
Abnormal Glycogen storage in hepatocytes.
No correction of fasting Hypoglycemia.
Hepatomegaly
Mild Ketosis.
Frequent feedings of Carbohydrate required.
Tauri's Disease

Enzyme Defect:
Phospho Fructo Kinase deficiency.(Of Glycolysis)

Biochemical alterations and manifestations:

Muscle Glycogenolysis is linked with muscle

Glycolysis.

PFK deficiency of Glycolysis accumulates Glucose-6

-PO4 in muscles.

Glucose-6-PO4 allosterically stimulates

Glycogenesis and inhibits Glycogenolysis which

accumulates Glycogen abnormally.

List Of Glycogen Storage Disorders


Type of Glycogen

Name of Glycogen Enzyme Defect

Storage Disorder

Storage Disorder

Type I

Von Gierke's Disease Liver Glucose-6-

Phosphatase

Type II

Pompe's Disease

Lysosomal (1-4)

Glucosidase

Type III

Cori's Disease

Debranching Enzyme

Type IV

Anderson's Disease

Branching Enzyme

Type V

Macrdle's Disease

Muscle Glycogen

Phosphorylase

Type VI

Her's Disease

Hepatic Glycogen

Phosphorylase

Lewi's Disease

Glycogen Synthase.

Type VII

Tauri's Disease

Phospho Fructo

Kinase.
Pneumonic To Remember

Very Private

Conversation At My

Home Lawn Table.

Hexose Mono Phosphate Shunt
Synonyms

HMP Shunt
Pentose Phosphate Pathway (PP

Pathway)

6-Phosphogluconate Pathway
Direct Oxidative Pathway
Dicken's Horecker Pathway
NADPH+H+ Generating Pathway.

HMP Shunt is an alternative

oxidative pathway of

Glucose.

It's a multifunctional

pathway.

It has no involvement of ATP.
Do not require Oxygen.
NADPH+H+ is generated.
HMP shunt is more

anabolic in nature and

generates:

vReducing equivalents-

NADPH+H+

vPentose Sugar-
Ribose-5-Phosphate.

In HMP shunt 6 molecules of

Glucose-6-PO4 makes its entry.

1 molecule of Glucose is oxidized
(6CO2+ 12 NADPH+12H+)
5 molecules of Glucose are

regenerated (Glyceraldehyde-3-

PO4 and Fructose-6-PO4).
NADPH+H+ generated in

HMP shunt supports

Lipogenesis.

Where in well fed condition

free and excess Glucose is

transformed to Fatty acid

and Cholesterol.

NADPH+H+ generated

in HMP shunt do not

enter in ETC and do

not produce ATPs.
Where HMP Shunt Operates?

Organs and Cel ular Site Of HMP

Shunt

Cytoplasm of Following Tissues:

Liver (30%)
Erythrocytes (30%)
Gonads (10%)
Adrenal Gland (10%)
Adipose Tissue (10%)
Lactating Mammary Gland (10%)
Condition Of Operation Of HMP

HMP shunt operates in

a well fed condition

after a heavy rich

Carbohydrate meals.

Reactions Of HMP Shunt
6(Glucose-6-PO4)+12NADP++6H2O

HMP Shunt

6CO2+12NADPH+12H++

2(Glyceraldehyde-3-PO4)+4(Fructose-6-PO4)

In HMP Shunt 6(Glucose-6-PO4)=
36 Carbon atoms.
6CO2 and 12 NADPH+H+ generated=
1 Glucose oxidation
30 Carbons are regenerated in the form of

2(Glyceraldehyde-3-PO4)
{ 2x3= 6 Carbons}
4(Fructose-6-PO4)
{4x6=24 Carbons}



HMP shunt includes two

irreversible oxidative

reactions NADP+ dependent.

Series of reversible non

oxidative sugar-phosphate interconversions

(3-7 carbon).
Transketolase transfers C2 units:

TPP requiring enzyme

Transaldolase transfers C3 units

Two enzymes control the

rearrangement of carbon skeletons

which result in the production of

Glyceraldehyde-3-phosphate and

Fructose-6-phosphate.

NADPH Producing Enzymes In

HMP Shunt

Glucose-6-P Dehydrogenase
6-P-Gluconate Dehydrogenase
Regulatory Enzyme Of HMP

Glucose-6-PO4 Dehydrogenase

(G6PD) is a regulatory enzyme of

HMP Shunt.

Insulin in well fed condition

stimulates this enzyme and

enhances the operation of HMP

Shunt.

NADPH+ H+ inhibits

Glucose -6- Phosphate

Dehydrogenase.
Significance Of HMP Shunt

HMP Shunt

predominantly and

uniquely produces

reducing equivalent ?

NADPH+H+
Uses of NADPH+H+

NADPH+H+ is used as a coenzyme for

reduction reactions catalyzed by enzyme

Reductases during reductive biosynthesis

of :

vFatty acids
vCholesterol
vSteroidal Hormones
vCertain Amino acids (GDH activity)

Role Of NADPH+H+ In RBC's
NADPH+H+ in RBC's serve as a

coenzyme for enzyme Glutathione

Reductase.

Glutathione Reductase of RBC's in

turn keeps an enzyme Glutathione

Peroxidase( H2O2 detoxifying

enzyme) in reduced and active state.


NADPH+ H+ in RBC's

indirectly helps in

detoxification of H2O2

This allows no accumulation

of H2O2 within RBC's.

In turn maintains cell

membrane integrity and

prevent hemolysis.


NADPH+ H+ in RBC's

keeps the Hemoglobin

iron in Ferrous (Fe+2)

state and prevents from

formation of

Methemoglobinemia


NADPH+ H+ is used in

detoxification of certain

drugs(Mono Oxygenase

System)through

Cytochrome P450 system.



Enzymes Requiring NADPH+H+
De novo Biosynthesis Of Fatty acids

Keto Acyl Reductase
Enoyl Reductase

Cholesterol Biosynthesis:

HMG CoA Reductase

In R.B.C's

Glutathione Reductase
Methemoglobin Reductase

In Detoxification Process:

Bilirubin Reductase
Cytochrome P450 Reductase

Uronic Acid Pathway

L- Xylulose Reductase
L- Gulonate Reductase
Ribose-5-PO4 another

important byproduct of

HMP Shunt is used for

biosynthesis of

Nucleotides, and certain

nucleotide coenzymes-

ATP,NAD,FAD and CoA

HMP Shunt is an unique multifunctional

pathway which involves interconversions

of sugars:

? 3 carbon (Glyceraldehyde-3-PO4)
?4 carbon(Erythrose-4-PO4)
?5 carbon (Ribose-5-PO4)
?6 carbon (Fructose-6-PO4)
?7 carbon(Sedoheptulose-7-PO4)
Inborn Error of HMP Shunt

OR

Glucose-6-Phosphate

Dehydrogenase Deficiency

Glucose -6-PO4

Dehydrogenase(G.6.P.D) is the

regulatory or key enzyme of HMP

shunt.

Persons with G.6.P.D deficiency

suffer from Hemolytic Anemia

and Hemolytic Jaundice.
G.6.P.D deficiency is sex linked

inherited.

G.6.P.D deficiency blocks HMP shunt

and decreases the levels of

NADPH+H+

Low levels of NADPH+H+ in cells impairs

the cell membrane integrity.

Lysis of RBC's- Hemolytic Anemia and

Hemolytic Jaundice.

Consequences Of G.6.P.D

Deficiency In RBC's
G.6.P.D deficiency in RBC's :

Decreases NADPH+H+ concentration.
Lowers Glutathione Reductase activity.
Lowers the active reduced form of Glutathione

Peroxidase.

Decreases detoxification of H2O2.
Increases H2O2 levels in cell.(Toxic free radical).
Increases Peroxidation of membrane PUFA's.
Looses cell membrane integrity.
Lysis of RBC membrane(Hemolysis).
Hemolytic Anemia ,Hemolytic Jaundice,

Methemoglobinemia.

Individuals with G.6.P.D deficiency

are Resistant to Malaria.

The Reasons for it are:
Low life span of R.B.C's.( Due to

abnormal hemolysis)

Incomplete life cycle of Malarial

Parasites in such defective

R.B.C's.


Persons with G.6.P.D

deficiency on ingestion of

Oxidant Drugs ?Primaquine,

Antipyretics (produces more

H2O2) aggravate the

condition and leads to

Hemolytic anemia.
Gluconeogenesis

Synonyms

Neo Glucogenesis.
Biosynthesis of Glucose.
Conversion of Pyruvate to Glucose.
Metabolism Of Lactate.
What Is Gluconeogenesis?

Gluconeogenesis is
Anabolic process
Carried out in the Cytosol of Liver,
In an emergency condition
Under the influence of hormones

Glucagon and Epinephrine

Biosynthesis of Glucose from non

Carbohydrate precursors.

Gluconeogenesis is the process whereby

precursors such as Lactate, Pyruvate,

Glycerol, and Glucogenic Amino acids are

converted to Glucose.

Fasting requires all the Glucose to be

synthesized from these non-carbohydrate

precursors.

Most precursors must enter the Krebs cycle

at some point to be converted to

Oxaloacetate.
? Humans consume 160 g of Glucose per

day

? 75% of that is used up in the brain
? Body fluids contain only 20 g of

Glucose

? Glycogen stores yield 180-200 g of

Glucose

? The body must still be able to make its

own Glucose

Where Gluconeogenesis Occur?
Organs and Cellular Site For

Gluconeogenesis:

Organs operating Gluconeogenesis:

Liver (Predominantly)
Renal Cortex (1/10)

Cellular Site:

Mitochondria and Cytoplasm.

When Gluconeogenesis Operated?
Gluconeogenesis predominantly takes place

When blood Glucose is low.
When cellular Glucose is deprived.
In between meals.
In response to Glucagon.

Physiologically In fasting/Starvation conditions.

Pathologically In Diabetes Mellitus

(In D.M low levels of Insulin and high levels of Glucagon)

Gluconeogenesis

provides Glucose in slow

and sustained manner in

response to fall in blood

Glucose.
Glucogenic/Non carbohydrate

Precursors

The source of Pyruvate and

Oxaloacetate for

Gluconeogenesis during fasting

or carbohydrate starvation is

Mainly from Amino acid

catabolism.
Pyruvate (Predominant precursor)
Lactate(Anaerobic and Erythrocyte

Glycolysis)

Propionyl-CoA
(oxidation of odd chain fatty acid and

Amino acid catabolism)

Glycerol (Lipolysis, TAG breakdown)
Glucogenic Amino acids
(Ala, Asp, Ser, Gly, Tyr, Trp, His)
Intermediates of TCA cycle

How Gluconeogenesis Occur?
Steps Of Gluconeogenesis

Glycolysis converts

Glucose to Pyruvate.

Gluconeogenesis

converts Pyruvate to

Glucose.
Gluconeogenesis and

Glycolysis are not exactly

same but differs in their

irreversible steps.

The reversible enzymes of

both the pathways are same.

? In Gluconeogenesis

? Seven steps of Glycolysis are

retained.

? Three steps are replaced.
Three irreversible enzymes of Glycolysis.

w Glucokinase
w Phosphofructokinase
w Pyruvate Kinase

These 3 steps are bypassed in Gluconeogenesis.

w Glucose-6-Phosphatase
w Fructose-1,6-Bis Phosphatase
w PEP Carboxy Kinase (GTP dependent)
w Pyruvate Carboxylase( Requires ATP and Biotin)

Oxaloacetate is the starting

material for Gluconeogenesis
Conversion of Pyruvate to

PEP

Is in two irreversible steps
With two enzymes
Requiring ATP and GTP


Pyruvate is converted to Oxaloacetate before

being changed to PhosphoenolPyruvate

1. Pyruvate Carboxylase catalyses the ATP-driven

formation of Oxaloacetate from Pyruvate and

CO2
2. PEP Carboxykinase (PEPCK) converts

Oxaloacetate to PEP that uses GTP as a

phosphorylating agent.

Pyruvate Carboxylase

? The reaction requires ATP and bicarbonate as

substrates

? Biotin cofactor
? Acetyl-CoA is an allosteric activator
? Regulation: when ATP or acetyl-CoA are high,

Pyruvate enters gluconeogenesis
PEP Carboxykinase

Not an allosteric enzyme
Rxn reversible in vitro but irreversible

in vivo

Activity is mainly regulated by control

of enzyme levels by modulation of

gene expression

Glucagon induces increased PEP

Carboxykinase gene expression

Fructose-1,6-Bisphosphatase

? Allosteric regulation:

? Citrate stimulates
? Fructose-2,6--Bisphosphate inhibits
? AMP inhibits


Glucose-6-Phosphatase

? Presence of G-6-Pase in ER of liver and kidney

cells makes gluconeogenesis possible

? Muscle and brain do not do gluconeogenesis
? G-6-P is hydrolyzed as it passes into the ER
? ER vesicles filled with glucose diffuse to the

plasma membrane, fuse with it and open,

releasing glucose into the bloodstream.
ATP Use In Gluconeogenesis

2 ATPs are used in Pyruvate Carboxylase

reaction of Gluconeogenesis.

2 GTPs are used in PEP Carboxykinase

step of Gluconeogenesis generated in

TCA cycle.

2 ATPs are used in Phospho Glycerate

Kinase activity.
Net 6 ATP's are utilized

during Gluconeogenesis

for biosynthesis of

1 Glucose molecule from
2 molecules of Pyruvate.

Entry Of Glucogenic Precursors

For Gluconeogenesis


Regulation Of Gluconeogenesis
Regulatory Enzymes Of

Gluconeogenesis

Four irreversible enzymes of

Gluconeogenesis are its regulatory

enzymes.

vPyruvate Carboxylase
vPEP Carboxy Kinase.
vFructose-1,6-Bis Phosphatase.
vGlucose-6- Phosphatase.

Gluconeogenesis and

Glycolysis are reciprocally

regulated ,i.e if one

pathway is active another

is relatively inactive.
In a well fed condition

Insulin inhibits

Gluconeogenesis.

In emergency condition

Glucagon stimulates

Gluconeogenesis.

To prevent the waste of a

futile cycle, Glycolysis &

Gluconeogenesis are

reciprocally regulated.
Glucagon via cAMP cascade of

reactions brings covalent

modification of enzymes.

Pyruvate Carboxylase.
PEP Carboxy Kinase.

Stimulate Gluconeogenesis.
Simultaneously Glucagon Inhibits

Pyruvate Kinase of Glycolysis.

Substrate Availability and

Regulation Of Gluconeogenesis
Increased availability of

Glucogenic precursors viz

Lactate ,Glycerol, products of

Glucogenic amino acids

influences the rate of

Gluconeogenesis.

Excess Acetyl-CoA in emergency

condition Al osterical y Stimulates

Gluconeogenesis
In fasting or emergency condition .
Glucose metabolism decreased.
Lipid metabolism increased.
Increased Lipolysis.
Increased Oxidation of Fatty acids.
Increased Acetyl-CoA.
Acetyl-CoA stimulates Pyruvate

Carboxylase for OAA synthesis.

Simulates Gluconeogenesis.

Acetyl-CoA regulates Pyruvate

Carboxylase

Increases in Oxaloacetate concentrations

increase the activity of the Krebs cycle

and Acetyl-CoA is an allosteric activator

of the Carboxylase.
However when ATP and NADH

concentrations are high and the Krebs

cycle is inhibited, Oxaloacetate goes

to Glucose.
Pyruvate Carboxylase

(Pyruvate Oxaloactate) is allosterically activated by

acetyl CoA.

[Oxaloacetate] tends to be limiting for Krebs cycle.

When Gluconeogenesis is active in Liver, Oxaloacetate

is diverted to form Glucose.

Oxaloacetate depletion hinders acetyl CoA entry into

Krebs Cycle.

The increase in [acetyl CoA] activates Pyruvate

Carboxylase to make Oxaloacetate.

Reciprocal Regulation By

Fructose-2,6-bisphosphate
The allosteric regulator

Fructose-2,6-

bisphosphate is

synthesized & degraded by

a bi-functional enzyme

that includes 2 catalytic

domains:

Fructose-2,6-

bisphosphate is

synthesized from excess

Glucose in well fed

condition.

w Fructose-2,6-bisphosphate

stimulates Glycolysis.
Fructose-2,6-bisphosphate

allosterically activates the

Glycolysis enzyme

PhosphoFructokinase 1(PFK1).


Fructose-2,6-

bisphosphate allosterically

inhibits the

Gluconeogenesis enzyme

Fructose-1,6-

bisphosphatase.



Significance Of Gluconeogenesis
Glucose is a primary source of energy.
Brain and Erythrocytes are totally

dependent upon Glucose for its energy in

all states.

Blood Glucose in fasting condition

should be maintained to 70-110 mg%.

Gluconeogenesis operates in critical

emergency conditions when blood

Glucose go below subnormal.

Gluconeogenesis

endogenously produces

Glucose in Liver using

non carbohydrate

precursors and regulate

blood Glucose levels.
Thus Gluconeogenesis corrects fasting

Hypoglycemia and try to maintain the

fasting blood Glucose of 70-110 mg%.

Gluconeogenesis helps in supply of Glucose

to Brain and Erythrocytes in emergency

condition and maintain their functions.

Gluconeogenesis by its operation

metabolizes Lactate, Propionyl CoA, and

Glycerol obtained from other metabolic

pathways.

Cori's Cycle

and

Glucose Alanine Cycle
Cori's cycle

metabolizes Muscle

Lactate produced in

anaerobic condition.

The Cori Cycle operates during

exercise.

Lactate produced from Pyruvate in

muscles in anaerobic condition ,passes

via the blood to the Liver, where it may

be converted to Glucose by

Gluconeogenesis.

The Glucose may travel back to the

muscle to fuel Glycolysis.


Glucose Alanine Cycle

(Cahil Cycle)

Glucose Alanine Cycle is

important during starvation.

Glucose Alanine cycle is

intimately related with Cori's

cycle.



The Cori cycle costs 6 ~P in liver for every 2 ~P made

available in muscle. The net cost is 4 ~P.
Although costly in ~P bonds, the Cori Cycle allows

the organism to accommodate to large fluctuations

in energy needs of skeletal muscle between rest and

exercise.
Energy dissipation by the Cori Cycle, which expends

6 ~P in liver for every 2 ~P produced via Glycolysis for

utilization within the tumor, is thought to contribute to

the weight loss that typically occurs in late-stage

cancer even when food intake remains normal.

GN Ratio or DN Ratio

Glucose Nitrogen

Ratio

Dextrose Nitrogen

Ratio
During Starvation Muscle

Proteins are degraded to release

Glucogenic precursors(G).

Nitrogenous Urea end product

of Protein catabolism excreted

out through urine(N).

GN ratio =3.65
1 gm of Urea nitrogen

produced will form 3.65 gm

of Glucose.

Protein contains 16%

Nitrogen.

58% of Protein is Glucogenic
G N ratio gives idea of

amount of body Protein

degradation which

provide precursors for

Glucose production in

emergency conditions.

GN ratio is enhanced in

Insulin deficiency
Increased body Protein degradation
Starvation
Pyrexia
Hyperthyroidism
Cancer
Uronic Acid Pathway
Significance Of Uronic Acid

Pathway

Uronic Acid Pathway is minor

Oxidative Pathway of Glucose.

Uronic Acid Pathway oxidizes Glucose

to Glucuronic acid.

UDP-Glucuronate is an activated

molecule produced in Uronic Acid

Pathway which has specific roles in the

body.
Functions of UDP-Glucuronate:

UDP-Glucuronate is a repeating

unit of Mucopolysaccharides/

Glycosaminoglycans of human

body.

UDP-Glucuronate is

component of Glycolipids-

Cerebrosides and Gangliosides.

UDP-Glucuronate

serve as a conjugating

agent for

detoxification reactions

in Liver.
Bilirubin in Liver is

conjugated with 2 molecules

of UDP-Glucuronate to form

Bilirubin di Glucuronide

[conjugated Bilirubin ]

Inborn Error Of Uronic Acid

Pathway
Essential Pentosuria is an inborn error

of Uronic Acid Pathway.

Essential Pentosuria is also a member of

Garrod's Tetrad.

Enzyme Defect:

Xylitol Dehydrogenase/L-Xylulose

Reductase.

Abnormally L-Xylulose(Pentose)

accumulated in blood and excreted out

in urine.

Galactose Metabolism
Sources of Galactose

Dietary Exogenous Source of

Galactose:

Lactose- Milk and Milk Products.
Digestion of Lactose by Lactase

liberates Galactose and Glucose.

Bodies Endogenous Source of

Galactose:

Breakdown product of GAG's,

Glycoprotein and Glycolipids.
Infants major food is

milk.

Galactose is equally

present along with

Glucose in their GIT.

Absorption And Fate Of Galactose
Galactose from an intestinal

lumen is actively absorbed

with relative coefficient of

absorption of 110.

Galactose absorbed in intestinal

mucosal cells diffuse into

Hepato Portal circulation and

carried to Liver.

Galactose in Liver is

metabolized and

transformed to Glucose.



Inborn Errors Of Galactose

Metabolism
Galactosaemia

Enzyme Deficient: Galactokinase

Biochemical Alterations:

Galactose not metabolized to Glucose.
No phosphorylation of Liver Galactose to

Galactose-1-PO4.

Free Galactose(permeable) from Liver, move

out in blood.

Galactosemia-Increased levels of Galactose

in blood.

Galactosuria-Galactose excreted in urine.

Galactosemia Leads To Cataract

In Galactosemia the high levels of

blood Galactose rich to eyes and get

accumulated.

In the lens cells the accumulated

Galactose is reduced to Galactitol.

Galactitol in lens cause opaqueness

of lens.

Causing Cataract.
Classical Galactosemia

Enzyme Deficient:

Galactose-1-PO4 Uridyl Transferase.

Biochemical Alterations and Clinical

Manifestations:

Blocks the conversion of Gal-1-po4 to UDP-Galactose.
Accumulation of Galactose-1-po4 in Hepatocytes.
Hepatomegaly
Splenomegaly
Loss of Weight
Weakness
Hepatic Jaundice.
Mental Retardation
Infants (Milk fed) whose

principle dietary

carbohydrate is Galactose

are more affected during

inborn error of Galactose

metabolism.

Fructose Metabolism
Sources Of Fructose

Fructose is present in free form in

Fruits and Honey.

Fructose is a component of Sucrose.
Sucrose digestion by Sucrase liberates

free Glucose and Fructose.

Endogenously Fructose is richly

present in seminal fluid.

Absorption and Fate Of Fructose

Fructose from intestinal lumen is

absorbed by facilitated diffusion.

From intestinal mucosal cells it is

carried to Liver by Hepato Portal

circulation.


In liver Fructose is

metabolized to Glucose

and utilized.
Inborn Errors Of Fructose

Metabolism

Essential Fructosuria

Enzyme Defect: Liver Fructokinase
Biochemical Alterations and Manifestations:

Blocks the phosphorylation of Fructose to Fructose-1-PO4.
Free Fructose is permeable ,come out of Liver.
High levels of Fructose in blood and urine.
Fructosuria.
Asymptomatic.
Restrict Sucrose and Fructose in diet.
Hereditary Fructose

Intolerance/Fructose Poisoning

Enzyme Defect:
Aldolase- B
Inheritance:
Autosomal recessive
Incidence:
1 in 20,000 births

Biochemical Alterations and Clinical

Manifestations:

Fructose-1-PO4 not further

metabolized and accumulates in

hepatocytes.

Affects normal functioning of Liver.
Depletion of inorganic

Phosphorous(pi).

Decreases Glycolysis ,Glycogenesis and

Gluconeogenesis.
Classical manifestations of hereditary

Fructose intolerance:

Hypoglycemia
Hepatomegaly.
Hepatic Jaundice.
Diagnosis:
Benedict's and Selivanoff's Test.
Management:
Diet free of Sucrose and Fructose.

Homeostasis Of Blood Glucose

OR

Factors Regulating Blood Glucose
What is Homeostasis?

Homeostasis is a

physicochemical process in the

body, where the altered levels

are tried to maintained to

normal levels.

Biochemical homeostasis means

keeping the biochemical

constituents within normal range.

Homeostasis of blood Glucose

means keeping the blood Glucose

within normal range.
Normal homeostatic

mechanism maintains

bodies health.

Defect in homeostatic

mechanisms leads to:

No corrections of altered levels

of biochemical constituents.

Biochemical constituents vary

from normal range leading to

hyper and hypo values.

Leads to Metabolic disorders.


Normal Ranges Of Blood Glucose:

Fasting Blood Glucose(F)= 70-110 mg%
(After 10-12 hours of fast)
Post Prandial(PP) Blood Glucose= 120-160mg%
(1 ? -2 hours after meals)
Random Blood Glucose= 80-140 mg%.
(Any Time of the day)
Homeostatic Factors Regulating

Blood Glucose:

Hormones

Blood Glucose Regulating Hormones:

Hypoglycemic/ Blood Glucose Lowering

Hormone/ Anti Diabetogenic :

INSULIN
Hyperglycemic/ Blood Glucose

Increasing Hormones Diabetogenic :

Glucagon
Epinephrine (Adrenaline)
Thyroid Hormone
Growth Hormone
Glucocorticoids.

Organs And Metabolic Pathways

Operating In It:

Liver ( Glucostatic Organ )
Muscles
Adipose Tissue
Kidney.
Healthy normal

functioning of organs and

the related metabolic

pathways is essential for

normal blood Glucose

regulation.

INSULIN


Incretin - Gut Hormones

Stimulates Insulin Secretion.

Gut hormones GIP (Glucose dependent

Insulinotropic Peptide) and GLP-1

(Glucagon Like Peptide-1) produced in

response to Glucose in intestine.

Incretin reach and activate the Pancreas

for robust Insulin secretion, in

anticipation of the rise in blood Glucose ,

after meals.
Hormone Insulin get secreted by

cells of Islets of Langerhans of

Pancreas in response to increased

blood Glucose levels in a well fed

condition:

Insulin helps in transportation

of Glucose in peripheral tissues.

Stimulates all the key or

regulatory enzymes of

metabolic pathways which

metabolizes the entered Glucose

in cells.
Insulin by its activity stimulates and

increases Glucose utilizing pathways in

well fed condition:

vGlycolysis.
vGlycogenesis
vLipogenesis
vHMP Shunt
vUronic Acid Pathway

Insulin by its activity

simultaneously inhibits and

decreases Glucose producing

pathways:

?Glycogenolysis
?Gluconeogenesis


Counter Regulatory Hormones

Glucagon ( From cells of islets of

Langerhans)

Epinephrine (Hypothalamic Glucoreceptors,

mediated by ANS)

Growth Hormone ( Anterior Pituitary)
Cortisol (Adrenal Cortex- mediated by ACTH)
All these hormones opposes the action of

insulin on Glucose use.
Glucagon and Epinephrine are most

important in the acute and short

term regulation of blood Glucose

levels.

Glucagon stimulates Liver

Glycogenolysis and Gluconeogenesis.

Epinephrine stimulates

Glycogenolysis and Lipolysis.

Epinephrine inhibits insulin

secretion.

Epinephrine inhibits insulin

mediated uptake of Glucose by

peripheral tissues.

Epinephrine is not so essential if

Glucagon is functioning.
Cortisol and Growth

Hormone are important

in the long term

management of Glucose

metabolism.

Insulin

Glucagon

Insulin is a polypeptide

Glucagon is a polypeptide

hormone composed of 51

hormone composed of 29

amino acids

amino acids.

Structure has two

Structure has one

polypeptide chains 21 and 30 polypeptide chain

amino acids.
Insulin is synthesized and

Glucagon is secreted by alpha

secreted by beta cells of Islets cells of Islets of Langerhans

of Langerhans of Pancreas.

of Pancreas.

Insulin is secreted in

Glucagon is secreted in

response to high blood

response to low blood

Glucose and Aminoacid

Glucose

levels.
Insulin

Glucagon

Epinephrine inhibits

Epinephrine stimulates

Insulin secretion

Glucagon secretion.

Insulin by its activity

Glucagon by its activity

lowers the blood

raises the blood Glucose.

Glucose. Insulin

Glucagon is Glucose

Glucose utilizing

producing hormone

hormone
Insulin stimulates all

Glucagon stimulates

pathways of Glucose

Glycogenolysis and

operating in a well fed Gluconeogenesis in

condition which

emergency fasting

metabolizes cellular

condition.

Glucose.Insulin

Glucagon

Insulin deficiency leads Glucagon deficiency

to persistent

leads to persistent

Hyperglycemia

hypoglycemia

Insulin for its action Glucagon for its

do not use cyclic AMP.activity uses cyclic

AMP.

Insulin stimulates

Glucagon stimulates

Glycogenesis,

Glycogenolysis,

Lipogenesis, Protein Lipolysis, Protein

biosynthesis.

degradation.
Homeostatic Mechanism Of Blood

Glucose:

In a well fed condition after heavy meals

Glucose added to blood

Increased blood Glucose(Transient Hyperglycemia)

Insulin secreted

Mediates Glucose uptake by peripheral tissues

(GluT4 Insulin dependent)

Regulates the increased blood Glucose
In a fasting condition /Between meals

Blood Glucose is utilized

Decreased blood Glucose(Transient Hypoglycemia)

Glucagon and Epinephrine secreted

Stimulates Glucose producing pathways of Liver

Glycogenolysis and Gluconeogenesis Increased

Glucose added to blood

Regulates the decreased blood Glucose

Significance Of Blood Glucose

Regulation
A constant source of blood Glucose

is an absolute requirement for

human life.

Glucose is the greatly preferred

energy source for Brain,

Erythrocytes.

Glucose is essential for exercising

muscles.

Homeostatic mechanism of blood Glucose :
Corrects transient hyperglycemia after a well fed

state.

Corrects transient hypoglycemia in a fasting

condition.

Maintain a constant normal range of blood

Glucose in specific conditions of body.

Helps in continuous supply of Glucose to tissues

which are totally dependent on Glucose.

Try to keep the Brain and Erythrocytes vital and

active
Disorders Of Blood Glucose

Regulation

Causes of abnormal blood

Glucose regulation:

Defects in Hormonal secretion

and their activities.

Diseased organ system.
Deranged metabolic pathways

associated to Glucose.
Defect in factors regulating

blood Glucose:

Does not correct transient

Hyperglycemia and

Hypoglycemia.

Leads to persistent

Hyperglycemia and

Hypoglycemia.

Persistent Hyperglycemia

Persistent hyperglycemia is characterized with

chronic abnormal high levels of blood Glucose.

Persistent Hyperglycemia is noted in:

Diabetes mellitus.
Stress, Anxiety
Hyperadrenalism
Hyperthyroidism
Hyperpituitarism
Persistent Hypoglycemia

Persistent hypoglycemia is characterized with

abnormal low levels of blood Glucose.

Persistent Hypoglycemia is noted in:

Prolonged Starvation
Tumors of pancreas
High dose of insulin during insulin therapy
Alcoholism

Types Of Hypoglycemia

Insulin ?Induced

Hypoglycemia

Post Prandial Hypoglycemia
Fasting Hypoglycemia
Alcoholic Intoxication-

Hypoglycemia
Insulin induced hypoglycemia-

High dosage of Insulin while

treating Type I Diabetes mellitus.

Glucagon is administered

subcutaneously or intramuscularly

to unconscious patients who have

lost the ability to coordinate

swallowing.

Post prandial Hypoglycemia-

Caused by exaggerated insulin

release after meals.

Transient hypoglycemia with mild

adrenergic symptoms.

Manage the condition by advising

the patients to take frequent small

meals rather than usual three large

meals.
Fasting Hypoglycemia-

In fasting condition.
In pancreatic tumors- large insulin

secretions.

Hepatic damage- low Glycogenolysis and

Gluconeogenesis

Adrenal insufficiency
Show Neuroglycopenic symptoms
Convulsions and Coma

Alcoholic Intoxication-

Hypoglycemia
Persons in fasting

condition(depleted stores of

Glycogen) intoxicated with alcohol.

Alcohol metabolism produces

abundance of NADH+H+

Alcohol metabolism inhibits

Gluconeogenesis.

Decreases the Glucose synthesis.

Consequences of Hypoglycemia

Transient hypoglycemia can

cause cerebral dysfunction.

Persistent ,prolonged

hypoglycemia causes brain

death.
Symptoms Of Hypoglycemia

Adrenergic Symptoms:
( Due to elevated epinephrine , when abrupt fall in

blood Glucose at 65 mg% )

Anxiety
Palpitation
Headache
Confusion
Tremors
Sweating
Neuroglycopenic Symptoms:
(Due to impaired delivery of Glucose to brain,

when blood glucose drops gradually at 50 mg%)

Slurred Speech
Seizures
Coma
Death

Hypoglycemia is more

serious than hyperglycemia.

Brain does not get sufficient

Glucose in hypoglycemic

conditions.

One should manage

hypoglycemia more rapidly

to avoid brain dysfunction.
Correction Of Hypoglycemia

Hypoglycemia is a medical emergency

which should be immediately attended

and resolved to have proper brain

function.

Administration of Glucose

intravenously resolves the symptoms

of hypoglycemia within minutes.

Hyperglycemia

Hypoglycemia

Blood glucose increased Blood Glucose decreased

above normal range.

below normal range.

Caused due to

Caused due to excess

insufficiency or

activity of Insulin.

inefficiency of Insulin.
Predominant in Diabetes Noted in Insulinomas

mellitus.
Hyperglycemia is less

Hypoglycemia is more

severe and do not affect serious , affects normal

brain function.

function of brain.

Hyperglycemia may lead Hypoglycemia condition

to Glycosuria.

shows no Glycosuria.


Diabetes Mellitus (DM)
What is Diabetes mellitus?

Diabetes mellitus is

Most common (3rd leading cause of death)
Heterogeneous, wide spread
Endocrine, metabolic disorder
Characterized by chronic persistent

hyperglycemia.

Causes/Etiological Factors:

Basic cause for Diabetes mellitus is :

Insulin insufficiency
Insulin inefficiency
Diabetes Mellitus is a

disorder due to defect

in blood Glucose

regulation.

Hormone Insulin

which regulates blood

glucose levels is

affected in Diabetes

mellitus.
Low/No insulin activity in

DM does not transport

Glucose within peripheral

cells leading to persistent

hyperglycemia.

Multiple and Complex Etiological

Factors Of Diabetes Mellitus:
Hereditary
Race
Nutritional Status
Stress
Drug Interaction
Endocrine Dysfunction
Infections
Autoimmunity
Occupational
Living Style
Various other Environmental Factors

Modern Life style ,food

habits, stress ,and

polluted environment

are likely to increase the

number of sufferers of

Diabetes Mellitus.
Geographical Distribution/

Prevalence Of DM

Diabetes mellitus is a substantial

global health problem.

Widely spreaded in every part of

world.

More than 20 million people are

sufferers of DM world wide.

Classification/Types Of DM

WHO Classification of Diabetes mellitus:

Type 1/IDDM/Juvenile Onset DM

Type 2/NIDDM/Maturity Onset DM

Gestational Diabetes mellitus(GDM)
Type 1 Diabetes Mellitus

Type 1 DM

Juvenile Onset
Initiated by environmental factor/ viral infection.
Abrupt onset
Cellular mediated autoimmune destruction of the

beta cells of the pancreas

Absolute deficiency of insulin secretion.
Insulin dependence
Ketosis tendency
Presence of islet cell autoantibodies, insulin auto

antibodies in blood circulation.


Type 2 Diabetes Mellitus

Type 2 DM

Maturity Onset Diabetes
Has resistance to Insulin
Insulin secretory defect
Not absolute insulin deficiency
Strong genetic predisposition
Prone to obese and sedentary life

persons

Milder type
Character

IDDM

NIDDM

Prevalence

10-20%

80-90%

Age Of Onset

< 20 Years

> 30 Years

Body Weight

Normal/Low

Obese/Over

weight

Genetic

Moderate

Very Strong

Predisposition
Defect

Insulin

Insulin

deficiency-

inefficiency-

Destruction of Insulin

cells of Pancreas Resistance ,

defect in Insulin

receptors.

Character

IDDM

NIDDM

Plasma Insulin Low or absent

Normal /

Increased

Auto Antibodies Frequently

Rare

found

Severity

More severe

Mild

Treatment

Insulin Doses

Hypoglycemic

Drugs.

Acute

Diabetic

Hyperosmolar

Complications Ketoacidosis

Coma

Ketosis

Ketosis

common.

Rare.


Gestational Diabetes Mellitus

(GDM)

Glucose intolerance during pregnancy.
Affects approximately 4 % of pregnant

women.

Caused due to metabolic and

hormonal changes during pregnancy

Women with GDM frequently return

to normal postpartum.
Gestational diabetes

mellitus (GDM) is defined

as any degree of glucose

intolerance with onset or

first recognition during

pregnancy .

Gestational diabetes is caused

when the insulin receptors do

not function properly.

GDM Leads to perinatal

complications.

GDM Increases risk to suffer from

DM in later life.
Perform a diagnostic oral

glucose tolerance test

(OGTT) without prior

plasma or serum glucose

screening.

Sample drawn after 100-gram glucose drink (glucose

load)

Time of Sample Collection

Target LEVEL

Fasting* (prior to glucose load)

95 mg/dL (5.3

mmol/L)

1 hour after glucose load

180 mg/dL (10.0 mmol/L)

2 hours after glucose load

155 mg/dL (8.6 mmol/L)

3 hours after glucose load*

140 mg/dL (7.8 mmol/L)

INDICATION: If two or more values meet or exceed the

target level, gestational diabetes is diagnosed.
Women with GDM has large

gestational age (macrosomic)

Infants born to mothers with

untreated GDM has following

complications:

vHigh birth weight ( < 4 kg)
vRespiratory Distress syndrome
vHypoglycemia
v Hypocalcaemia
v Hyperbilirubinemia
Remember that women

diagnosed with GDM can

develop diabetes later onn in

their life.

Hence they are advised to

undergo annual screening to

enable early diagnosis or to rule

out the condition.

Risk Factors to Develop DM
The development of type 2 diabetes

is caused by a combination of

lifestyle and genetic factors.

While some are under personal

control, such as diet and obesity.

Others, such as increasing age,

female gender, and genetics are

not under personal control.

A lack of sleep has been

linked to type 2

diabetes. This is believed

to act through its effect

on metabolism.
The nutritional status of a

mother during fetal

development may also play a

role, with one proposed

mechanism being that of

altered DNA methylation.

A number of lifestyle factors are known to

be important to the development of type 2

diabetes, including:

Urbanization
Stress
Obesity(defined by a body mass index of

greater than thirty)

Excess body fat
Lack of physical activity/Lack of exercise

is believed to cause 7% of DM cases.
Dietary Factors

Very poor diet increases

risk of DM.

Very excess consumption of

sugar-sweetened drinks in

excess is associated with an

increased risk of DM.

Eating lots of white rice

appears to also play a role in

increasing risk of DM.


The type of fats in the diet are

also important:

Dietary Saturated fats and

trans fatty acids increases

the risk of DM.

Dietary Polyunsaturated

and monounsaturated fat

decreasing the risk of DM.
Biochemical Alterations In DM

In Type -1 Diabetes

mellitus there is

destruction of beta cells

of islets of Langerhans

which leads to absolute

deficiency of insulin.
In Type -2 Diabetes

mellitus membrane

Glucose transporter

GluT4 is reduced which

leads to insulin resistance.

Metabolism Deranged In DM

Diabetes mellitus chiefly alters and

affects Carbohydrate metabolism

which in turn affects the interdependent

?Lipid Metabolism
?Protein Metabolism
?Water and Mineral Metabolism
Diabetes mellitus exhibits

Starvation of peripheral cells

(Scarcity In Plenty).

Chronic Persistent Hyperglycemia

In DM

Due to low or poor/decreased Insulin

activity in Diabetes mellitus.

Decreased uptake of blood Glucose by

peripheral tissues.

Underutilization Of Glucose.
Due to more/increased Glucagon

activity.

Over production of Glucose.
Chronic persistent hyperglycemia.

Decreased Utilization of Cellular

Glucose In DM

As Insulin is low in its activity in DM.
There is decreased stimulation of

following pathways:

vDecreased Glycolysis
vDecreased TCA cycle
vDecreased Glycogenesis
vDecreased Lipogenesis
vDecreased HMP shunt.
Increased Lipolysis,

Gluconeogenesis and Ketogenesis

In Type 1 DM

Low insulin in body of DM
More Glucagon in body of DM
Glucagon stimulates :

?Increased Lipolysis
?Increased Gluconeogenesis
?Increased Ketogenesis
? (Incomplete Fatty acid Oxidation)

Renal Osmotic Glycosuria In DM

Blood Glucose levels when crosses renal

threshold value for Glucose=180 mg%.

The presence of high Glucose in renal

tubules exerts an osmotic effect.

Reduces reabsorption of water.
Excretion of Glucose along with water -

Glucosuria (Osmotic Diuresis).
Decreased Protein

Synthesis

and

Increased Protein

Breakdown

In DM

Low insulin activity inhibits protein

biosynthesis and stimulates muscle

protein breakdown in a body

suffering from Diabetes Mellitus.

The Glucogenic Aminoacids released

from Protein breakdown produces

Glucose in Liver via Gluconeogenesis.

Excess Protein breakdown makes

the person emaciated and loose

weight.
Increased Serum TAG, Cholesterol

and Ketone bodies In D.M

Hypertriglyceridemia in DM is

due to:

Increased Lipolysis
Decreased Lipoprotein Lipase

activity.
"Fat Burns Under The Flame Of

Carbohydrate"

For complete oxidation of body fat there

needs a sufficient cellular Carbohydrate

metabolism.

Low cellular Carbohydrate metabolism in

DM, exhibit incomplete metabolism of

Fats.

In Diabetes mellitus there is less

cellular Carbohydrate metabolism

Excess but incomplete fatty acid

oxidation

More production of Ketone bodies

which are partial oxidized products

of fat metabolism.
More deficiency of Insulin.
More deprivation in cellular Glucose

metabolism.

More incomplete/partial fat oxidation.
More Ketone bodies production.
Accumulation of Ketone bodies in

blood- Ketonemia.

Ketone bodies excreted in Urine-

Ketonuria.

Uncontrol ed DM shows Ketosis

Uncontrolled Diabetes Mellitus is a

serious condition of DM.

Very low Insulin activity.
Very deranged metabolic activity.
Ketonemia + Ketonuria =Ketosis
Kassumals breathing-Acetone Breath.
Acidosis-Ketoacidosis.
Diabetic Ketoacidosis.


Water Electrolyte and Acid Base

Imbalance In DM

Osmotic Diuresis in Diabetes Mellitus
Water Loss- Dehydration.
Electrolyte Loss
Ketoacidosis- Acid Base Imbalance.


Clinical Manifestations Of DM

Polyuria - Osmotic Diuresis.
Polydypsia - Thirst (Due to Dehydration).
Polyphagia ? Cellular Starvation ? (Stimulate Hunger centre)
Weakness
Lethargy
Weight Loss.
In serious conditions Coma.
Other symptoms that are commonly

present at diagnosis include:

A history of blurred vision
Itchiness and Burning sensation.
Peripheral neuropathy
Recurrent vaginal infections, and

fatigue.

Fatty Liver is noted in Type 2

Diabetes mellitus

Increased influx of fatty acids in

Liver.

Decreased VLDL formation in

Liver.

Decreased mobilization of lipids

out from Liver.
Increased Protein Glycation in DM

Due to increased circulating blood

Glucose.

There is increased glycation of

body proteins.

This interferes normal function

and turn over of Proteins.

Glycation of Hemoglobin (HbA1c),

affects oxygen transport.

Glycation of Albumin affects its

transport function.

Glycation of Apolipoprotein ?B ,

affects LDL metabolism and increases

atherogenesis.

Decreases elasticity of blood vessels.
Advanced Glycation

End(AGE) Products

increases free radical

generation.

Enhanced Oxidative Stress

in Diabetes mellitus.

Complications

Of

Diabetes Mel itus
Individual suffering from

Diabetes mellitus with poor

Glucose control for many

years develop from its

Complications.

A person with Diabetes

mellitus with good

control of his blood

Glucose is at low risk for

complications of DM.
Diabetes mellitus

developed with serious

complications, making it

a dreadful disease.

Causes for DM Complications:

High Glucose in blood circulation

and body fluids, exerts high osmotic

effect in blood vessels and renal

tubules.

Osmotic Diuresis in renal tubules.
High Sorbitol(Reduced form of

Glucose) accumulates in eyes and

causes Cataract.
Poor energy supply to

tissues make the organ

system weak.

Defective Immune System.
More susceptible and

compatible environment for

bacterial growth.

High circulation of blood lipids-

hyperlipidemias increases risk of

Atherosclerosis.

High levels of Ketone bodies in

blood and urine- Ketosis.
Long standing complications

develop in insulin independent

tissues like

Brain ( Brain Dysfunctions and Stroke)
Erythrocytes ( Low Oxygen Transport and

Unloading of Oxygen)

Eye Lens ( Diabetic Cataract)
Peripheral Nerves (Diabetic Neuropathy)
Kidney (Diabetic Nephropathy)
Liver (Fatty Liver)


Delayed Complications Of DM

Cardio Vascular Disorders

Atherosclerosis
Myocardial Infarction ( Painless MI Attack)

Retinopathy
Cataract
Stroke
Autonomic and Sensory Motor Dysfunction
Nephropathy
Foot Ulcers ?Gangrene
Type 2 Diabetes is typically a

chronic disease associated

with a ten-year-shorter life

expectancy.

Two to four times the

risk of cardiovascular

disease, including

ischemic heart disease

and stroke in persons

suffering from DM.
20-fold increase in

lower limb

amputations, and

increased rates of

hospitalizations.

In the developed world, and

increasingly elsewhere, type

2 Diabetes is the largest

cause of non traumatic

blindness and kidney

failure.


It has also been associated with

an increased risk of neurological

disorders:

Cognitive dysfunction and

dementia through disease

processes such as

Alzheimer's disease and

vascular dementia.



Other complications

include:

Sexual dysfunction
Frequent infections
Acute Complication Of DM

Diabetic Ketoacidosis
(Type 1DM)
Hyper Osmolar Nonketotic Coma.
(Type 2 DM,BGL> 900mg%)

People with type 2 diabetes

mellitus may rarely present with

Nonketotic Hyperosmolar coma

(a condition of very high blood

sugar associated with a

decreased level of consciousness

and low blood pressure)
Diagnosis Of Diabetes Mellitus

Urine Analysis

Glucose ?
Semi Quantitative Benedict's Test- Checks

Glucosuria.

Ketone Bodies-
Rothera's Test- Checks Ketonuria.

Blood Glucose Estimation:

GOD -POD Method.

Fasting Blood Glucose
Post Prandial Blood Glucose

Diabetic cut off for DM is 126mg%

in the fasting sample on two

different occasions.

Glucose

Tolerance Test

(GTT)
Diagnostic Tests to assess

Long term complications of

Diabetes mel itus:

? Blood Urea
? Serum Creatinine
? Urinary Protein
? Microalbuminuria
( 300 mg/24 hr of urine)

? Urinary Albuminuria > 300 mg/day is most

diagnostic for Diabetic Nephropathy.
Lipid Profile-

Serum TAG
Serum Cholesterol-
Serum LDL and HDL
Results of Lipid profile assess the

risk of macrovascular complications

CVD in Diabetes Mellitus.

Diagnostic Tests

To Assess

Long Term And Short Term

Glucose Control
Estimation of Glycosylated

Hemoglobin (HbA1c)

Gives index of Glucose control

in DM in last 4-6 weeks.

(Half life of RBC's 120 days).

Methods to measure Glycated

Hemoglobin:

Methods based on structural

differences:

Immunoassays
Affinity Chromatography

Methods based on charge differences:

Ion exchange Chromatography
Isoelectric focusing
HPLC


Fructosamine ? Quantitation

of Glycosylated Proteins.

Gives index of Glucose control

in DM in last 2-3 weeks.

( Half life of Albumin 20 days).
Estimation of Blood

Insulin levels
Islet Autoantibodies
Insulin Autoantibodies

Self Monitoring Of Glucose

In cases of Type 1 D M patients
For tight blood Glucose control
To minimize complications of DM.
By Accu Check-Glucometer
By Uri Stics -
Glucostics , Albustics , Ketostics.
Treatment Of DM

Diabetes mellitus is not a curable

disease.

Treatment or Management of

Diabetes mellitus is

Controlling the blood Glucose

levels within normal range.

Management Of IDDM

Diet Control- Foods with low

Glycaemic Index.

Weight to be improved- Good

Protein diet.

Insulin therapy- Adjust Insulin

dose w.r.t BGL.
Monitoring of the patients

during Insulin therapy:

Insulin therapy lowers serum

potassium levels (Hypokalemia)

check and correct for it.

High doses of Insulin may lead to

hypoglycemia have a check.

Management Of NIDDM

Diet Control.
Exercise to loose weight.
Use of Hypoglycemic Drugs
Hypoglycemic Drugs

Sulfonylureas- Glipizide (Glucotrol),

Glyburide (Diabeta), Tolazamide (Tolinase)

Meglitinides-Replaglinide (Prandin)
Biguanides- Metformin (Glucophage)
Butamide
Thiazolidinediones (TZDs)-Rosiglitazone

(Avandia)

Incretin mimetic- Exenatide

Oral Medication Mechanisms:

Increases insulin production.

Improves insulin receptor

sensitivity.

Inhibits Gluconeogenesis.

Inhibits Carbohydrate

absorption from GIT.
Prevention Of Diabetes Mellitus

Onset of Type 2 Diabetes can be

delayed or prevented through:

Proper nutrition ? Balanced diet
Diet high in green leafy vegetables
Limiting the intake of sugary

drinks

Regular Exercise


Balanced lifestyle may

reduce the risk by over

half

Avoid stressful life- being

Spiritual,Organized and

Ethical.
Glycosuria

Glycosuria is a

pathological condition

Detectable amount of

sugar is excreted out

through urine.

Causes For Glycosuria:

Increased levels of blood sugar

over their renal threshold values.

Defect in renal tubules lowering

the renal threshold values of sugars.

Renal threshold value for

Glucose = 180 mg%.
Types Of Glycosuria

Glucosuria (Most Common)
Fructosuria
Galactosuria
Pentosuria

Diabetic/ Hyperglycemic Glycosuria
Alimentary Glycosuria
(GIT absorption defect)
Emotional Glycosuria
(In anxiety, stress, anger)
Renal Glycosuria
(Renal tubular defect, low renal threshold value)
Detection And Confirmation Of

Glycosuria:

Semi Quantitative

Benedicts Test on

Urine Specimen.

Observations Of Semi Quantitative

Benedicts Test

No change in test color

Negative Test-

No Glycosuria

Green color Precipitate 0.5 % Glucose

(Cu2O)

present

Yellow color Precipitate

1% Glucose

present

Orange color Precipitate

1.5 % Glucose

present

Red color Precipitate

2% or more

Glucose present.
Glucose Tolerance Test

(GTT)

What Is GTT?
Glucose Tolerance Test (GTT)
Is a special investigation
Carried out in a Clinical

Biochemistry Laboratory

To check the bodies tolerance

towards a high dose (75gm) of

Glucose in a fasting condition.

Normal Tolerance ?

v Normal Blood Glucose

v No Glycosuria
Decreased Tolerance ?

v Increased Blood Glucose
v May have Glycosuria

Increased Tolerance ?

v Decreased blood Glucose
v No Glycosuria
Indications Of GTT

OR

When GTT Is Prescribed ?

In a case which is unclear-

Has symptoms of Diabetes

Mellitus but normal BGL.

To diagnose Gestational

DM(GDM) during pregnancy.

To find out severity of DM
To rule out renal Glycosuria.
Types Of GTT

Oral GTT

Oral dosage of Glucose given

during test.

Intravenous GTT

In GIT disordered persons,

Glucose dose is infused

intravenously.
Mini GTT

The duration of GTT is reduced to 1

? hrs.

Corticosteroid Stressed GTT

GTT is tested after dosage of

corticosteroids.

Preparation of a Person

for GTT

OR

Advice Given To a Person

Prior to GTT
A week prior to the appointed date for

GTT, the person is advised for:

Eat normal Carbohydrate diet

Do Not fast or starve

Do no strenuously exercise

Drink no Alcohol

Take no medications

The person is advised to

come in fasting

condition (10-12 hrs fast)

on the test date.
Procedure Of Oral GTT

Collect a fasting blood

and urine specimen

from the person

undergoing GTT.

Label the collected

fasting samples (F)
Note the time
Give an oral dose of Glucose

75 gm with 250 ml water/1.5

gm per kg body wt.

May flavor with lemon to

avoid vomiting.

From the time of dosage with

an interval of 30 minutes collect

the blood and urine specimens

up to 2 1/2 hrs or 150 minutes.

Label each collected specimen.
Analyze all the collected

specimens.
Blood specimens are analyzed

to estimate Glucose

concentration (Using GOD-

POD method).

Urine specimens are checked

for qualitative

presence/absence of Glucose

(Benedicts Test)

Record the readings of

blood Glucose for every

specimen

Plot a GTT curve on

graph paper and interpret

the results.


Plot a GTT Curve

Specimens

Blood

Urine

Glucose

Glucose

Fasting

75 mg%

Absent

30 minutes

100 mg%

Absent

60 minutes

120 mg%

Absent

90 minutes

145 mg%

Absent

120 minutes

1 20 mg%

Absent

150 minutes

85 mg%

Absent
Plot a GTT Curve

Specimens

Blood Glucose Urine Glucose

Fasting

160 mg%

Absent

30 minutes

170 mg%

Absent

60 minutes

200 mg%

Present

90 minutes

240 mg%

Present

120 minutes

230 mg%

Present

150 minutes

180 mg%

Present

Question

Why there is need of

continuous and uninterrupted

Glycolysis in RBC's?

To maintain RBC membrane

integrity and avoid destruction

and lysis of RBC's.

RBC membrane structure
The RBC membrane

Located in the

membrane are

proteins that

function as cationic

pumps.

The RBC maintains its volume and

water homeostasis by controlling the

intracellular concentrations of Na+ and

K+ via these cationic pumps which

require ATP.

ATP is also required in the Ca++

pump system that prevents

excessive intracellular build-up of

Ca++.
In ATP depleted cells there is

an intracellular build up of

Na+ and Ca++ and a loss of K+

and water.

This leads to dehydrated, rigid

cells that are destructed/ lysed

and culled by the spleen.

Any abnormality that

increases membrane

permeability or alters

cationic transport may

lead to decreased RBC

survival.
The major peripheral protein in

RBC's is Spectrin

It binds with other peripheral

proteins such as Actin to form a

skeleton of microfilaments on the

inner surface of the membrane.

This strengthens the membrane

and gives it its elastic properties.

For Spectrin to participate in

this interaction, it must be

phosphorylated by a protein

kinase that requires ATP.

Thus, a decrease in ATP

Decreased Phosphorylation

of Spectrin.
Unphosphorylated

Spectrin can no longer bind

to Actin to give the

membrane its elastic

properties.

This then leads to a loss in

membrane deformability and

a decreased RBC survival time.

Pasteur And Crabtree Effects
Study findings of Glucose

metabolism (Catabolism)

in Yeast Saccharomyces

cerevisiae under both

aerobic and anaerobic

condition.

Experimental findings of Glucose

metabolism in Yeast cells in

different concentrations of:

vOxygen
vSugar
Yeast's are ubiquitous

unicellular fungi.

Most yeast cells are of

facultative fermentative.

Types of Yeast

Non fermentative ?Has exclusively

respiratory metabolism (aerobic), not

capable of alcohol fermentation.

Obligate fermentative- Natural respiratory

mutants metabolize Glucose only through

alcoholic fermentation.

Facultative fermentative- Fully respiratory

or fermentative metabolism or both

respiratory and fermentative mechanism.
Yeast Sugar Metabolism

Yeast sugar metabolism

depends on:

Growth condition

qType and concentration of

Sugar

qOxygen concentration

Metabolic flux occurs on the

Pyruvate branch point.

Pyruvate is oxidized via TCA in

aerobic condition.

Pyruvate is reduced/ fermented

to Lactate or ethanol in

anaerobic condition.


Pasteur effect

Word origin: named after its

discoverer Louis Pasteur.
In 1861 Louis Pasteur figured out
In the absence of oxygen, yeast

consumes more glucose than in

the presence of oxygen.

A phenomenon that has become

known as Pasteur effect in the

literature.

Pasteur effect explains the

inhibiting effect of oxygen

on the process of

fermentation.
Oxygen inhibits Glycolysis.
Oxygen limits the use of Glucose.
In aerobic Glycolysis more ATP

produced inhibits PFK of Glycolysis.

In aerobic condition no fermentation

occurs.

In aerobic condition there is no

production of Ethanol/Lactate.

This shift from slow aerobic to rapid

anaerobic consumption of glucose was

first noted by Pasteur.

This shift also happens anytime you

are unable to provide oxygen to your

own mitochondria- they consume

Glucose faster in an attempt to produce

ATP via the less efficient fermentation

to lactate, and lactic acid accumulates

in your muscles.
He found that aerating yeasted broth

caused the yeast cell growth increased

while fermentation rate decreased.

A switch from anaerobic to aerobic

conditions results in the decrease in

the rate of carbohydrate breakdown in

yeasts.

Citrate and ATP, allosteric inhibition

of the PFK 1 enzyme explains the

Pasteur effect.

Pasteur effect is defined as

inhibition of fermentation

pathway by respiration

(Oxygen).

Oxygen inhibits

fermentation(Ethanol/Lactate

production) and reduces the

rate of Glycolysis.
Fermentation occurs

in anaerobic conditions.

Later studies reported several misinterpretations

related to the results of Pasteur effect.

Stated that results of Pasteur were an artefact due

to anaerobic growth impairment.

Anaerobic fermentation occurred in yeast entered

in stationary or resting phase.

Anaerobic fermentation occurred in sugar limiting

continuous culturing and at resting cell condition.

Production of alcohol occurs when cells are in

growth / lag phase.
In presence of high

concentration of Glucose ,the

Pasteur effect does not work.

Under this condition the

degradation of Glucose is via

fermentation to produce

ethanol in aerobic condition.

Crabtree Effect
Named after the English

Biochemist

Herbert Grace Crabtree.

Crabtree effect is

the converse of the

Pasteur effect.
The Crabtree effect(1929) describes

the phenomenon whereby the

Yeast, Saccharomyces cerevisiae,

produces ethanol (alcohol)

aerobically in the presence of high

external glucose concentrations

rather than producing biomass via

the Tricarboxylic acid cycle.

Crabtree effect defines

occurrence of alcoholic

fermentation under aerobic

conditions.

Saccharomyces cerevisiae

catabolize Glucose mainly by

fermentative process.
When oxygen supply is kept constant

and Glucose concentration is increased,

the oxygen consumption by cells falls.

Cells with high rate of Glycolysis

consumes pi and NAD+ which limits

their availability to operate oxidative

phosphorylation.

Here ETC/ oxidative phosphorylation

decreases and that decrease oxygen

consumption.

At high Glucose concentration the rate

of aerobic fermentation is also

increased.

At high concentration of Glucose there

is inhibition of synthesis of ETC

enzymes by high fermentation rates.

High rate of Glycolysis reduces the

respiratory chain and induces

fermentation to produce alcohol.

Catabolite repression of ETC enzymes.

Mechanisms Explaining

Crabtree Effect

v Catabolite Repression
v Catabolite Inactivation
v Limited Respiration

Capacity

Catabolite Repression

When Glucose/ initial

product of Glucose

metabolism suppress the

synthesis of various

enzymes of respiration( Still

unclear).
High concentration of

sugar disrupts the

structure of yeast

mitochondria.

Respiration is stopped

Ethanol fermentation

occurs.

Catabolite Inactivation

Glucose in high

concentration inhibits the

key enzymes of respiratory

track.
Crabtree effect in Yeast

cell can be observed when

the growth medium

containing Glucose in

concentration above 5mM.

Increasing concentrations of Glucose

accelerates Glycolysis (the breakdown

of glucose) which results in the

production of appreciable amounts of

ATP through substrate-level

phosphorylation.

This reduces the need of oxidative

phosphorylation done by the TCA cycle

via the electron transport chain and

therefore decreases oxygen

consumption.
The effect can be easily

explained, as the yeast being

facultative anaerobes can

produce energy using two

different metabolic pathways.

While the oxygen concentration

is low, the product of Glycolysis,

(Pyruvate), is turned into ethanol

and carbon dioxide, and the energy

production efficiency is low

(2 moles of ATP per mole of

glucose).
If the oxygen concentration grows,

Pyruvate is converted to acetyl CoA

that can be used in the citric acid cycle,

which increases the efficiency to 32

moles of ATP per mole of Glucose.

Therefore, about 15 times as much

glucose must be consumed

anaerobically as aerobically to yield the

same amount of ATP.

Under anaerobic

conditions, the rate of

Glucose metabolism is

faster, but the amount of

ATP produced (as already

mentioned) is smaller.
When exposed to aerobic

conditions, the ATP production

increases and the rate of Glycolysis

slows, because the ATP produced

acts as an allosteric inhibitor for

Phosphofructokinase 1, the third

enzyme in the Glycolysis pathway.

So, from the standpoint of ATP

production, it is advantageous

for yeast to undergo Krebs Cycle

in the presence of oxygen, as

more ATP is produced from less

Glucose.
When Glucose concentration is high in aerobic

condition:

Yeast fermentation in aerobic condition has limited

capacity.

High Glucose concentration
Increases Glycolysis
Increased Pyruvate concentration
Limits the yeast to use Pyruvate in line of TCA and

oxidative phosphorylation.

Pyruvate is fermented to Ethanol.

When Glucose concentration is

high in anaerobic condition:

Yeast fermentation in anaerobic

condition has unlimited

capacity.

Use all Pyruvate generated from

Glycolysis to Ethanol

unlimitedly.
Crabtree phenomena occurs

in tumor cells where cell is in

the aerobic condition

metabolizes Glucose

excessively via Glycolysis and

produces Lactate.

QUESTIONS
I) Long Answer Questions.

Q.1 Give principle carbohydrates

present in the diet & its rich

food sources. Describe the

digestion & absorption of

different carbohydrate forms.

Q.2 Define Glycolysis. Describe

reactions, Energetics, significance,

regulation of Glycolysis.

OR

Describe E.M.P. pathway

(Conversion of Glucose to Pyruvate).
Q.3 Describe Glycogen metabolism

& its regulation.

OR

Describe Glycogenesis and its

regulation

Describe Glycogenolysis and its

regulation.

Q.4 Describe T.C.A. cycle/Kreb's

cycle/Amphibolic pathway/Common

metabolic pathway.

OR

How Acetyl-CoA is oxidized in the

body & give its significance.

Q.5 Describe H.M.P. Shunt & Give its

significance.

OR

Describe Pentose Phosphate Pathway.
Q.6 Define Gluconeogenesis. Describe

the reactions of Gluconeogenesis.

State the fate of the Glucogenic

precursors .How Gluconeogenesis is

regulated.

Q.7 Describe Diabetes Mellitus with

respect to clinical types, causes,

biochemical alterations, clinical

manifestations, diagnosis &

management.

Q.8 Homeostasis of blood glucose

level by hormonal & metabolic factors.


II) Short Notes

Lactose Intolerance
Dietary cellulose & its importance.
Role of Insulin in Carbohydrate

metabolism.

Fates of dietary Glucose entered in the

Liver cells.

Difference between Insulin & Glucagon.

Glycogen storage disorders/Inherited

disorders of Glycogen Metabolism.

Difference between EMP & HMP

pathways.

G-6 P. D. deficiency.
Uronic Acid Pathway & its significance.
Metabolic fate of Fructose
Rapaport Leubering

Cycle/Glycolysis in Erythrocytes.

Oxidative Decarboxylation of

Pyruvate/Pyruvate Dehydrogenase

Complex.

Glycogenolysis in Muscles & Liver.
Cori's Cycle/Metabolism of Lactate.

Metabolic fate of Galactose
Galactosemia.
Glycosuria.
Difference between Hyperglycemia

& Hypoglycemia

Glucose Tolerance Test.
Inborn errors of Carbohydrate

Metabolism.

Glucose Transporters
Glucose Alanine Cycle
Glycaemic Index of Foods and

their importance

G: N /D:N ratio
Differentiate between IDDM

and NIDDM

Role of HMP Shunt in

Erythrocytes.

NADPH+H+ requiring enzymes.
Site & significance of Rapaport

Leubering cycle.
Short Answer Questions



Define substrate level phosphorylation.

Give examples of it.

Calculate the Energetics of Glycolysis

in Aerobic & Anaerobic condition.

Write formation and fates of Pyruvate

in the body.

Calculate the Energetics of complete

oxidation of 1 glucose molecule.

Give the Regulatory enzymes of

following pathways -

Glycolysis
HMP Shunt
Gluconeogenesis
Glycogenesis
Glycogenolysis
Glycosidases & their

role/Glycosidases their action &

products in GIT.

Enumerate disorders of

carbohydrate metabolism with

respect to biochemical defect &

biochemical alterations.

Write the enzymes &

coenzymes of PDH and KDH

complex.

Enumerate the diagnostic tests

for Diabetes mellitus.

Give four factors, which

regulate blood glucose.
Write various pathways of

carbohydrate metabolism

with respect to occurrence/

location (where), condition

(when), significance (why).

Pasteur and Crabtree effect

Case Studies
Case Study 1

A 58 year old obese man with

frequent urination is seen by his

primary care physician. The

following laboratory tests were

performed.

Random blood Glucose= 225 mg%
Urine Glucose 2+
Urine Ketones Negative
Questions

What is probable diagnosis of this

patient?

What other tests should be

performed to confirm this?

After diagnosis what test should be

performed to monitor his

condition?

Case Study 2
An 18 yr male who had an history of

Diabetes mellitus was brought to an

emergency department because of

excessive drowsiness , vomiting and

diarrhea .His Diabetes had been well

controlled with 40 units of Insulin daily

until several days ago . When he

developed excessive thirst an Polyuria.

For past three days he also had

headache, myalgia, and low grade fever

. Diarrhea and Vomiting began one day

ago.

Questions

What is the probable diagnosis of this

patient based on the data presented?

What laboratory tests should be performed

to manage this patients condition?

Why are urine ketones positive?
What methods are used to detect urine

ketones? Which ketone body is detected?
Case Study 3

A 14 yr old male student was seen by his

physician. His chief complaints were fatigue,

weight loss, and increase in appetite , thirst

and frequency of urination . For the past

three to four weeks he had been excessively

thirsty and had to urinate every few hours.

He began to get up 3 to 4 times a night to

urinate . The patient has family history of

Diabetes mellitus.

Fasting Blood Glucose=160 mg%
Glycosuria and Ketonuria detected.
Questions

Based on the preceding information can this

patient be diagnosed with Diabetes

mellitus?

What further tests might be performed to

confirm the diagnosis?

According to ADA what criteria are

required for the diagnosis Of Diabetes

mellitus?

Assuming this patient has diabetes which

type would be diagnosed?

Diagnostic Criteria For DM

Random Blood Glucose

> 200 mg%

+ Symptoms of DM

Fasting Blood Glucose

>126 mg%

Post prandial Blood Glucose > 200 mg%
Case Study 4

A 13 year old girl collapsed on a play ground

at school. When her mother was contacted

she mentioned that her daughter had been

loosing weight and making frequent trips to

the bathroom in the night. The emergency

squad noticed a fruity breath. On entrance

to emergency dept her vital signs were as

follows:

B.P -98/50
Body Temp 99 degree
Respirations Rapid
Urine PH

5.5

Urine Protein

Negative

Urine Glucose

4+

Urine Ketones

Present

Blood Glucose

500 mg%

Blood Urea

30 mg%

Serum Creatinine

0.4 mg%

Questions

Identify the patients most likely

type of Diabetes mellitus?

What is the cause of fruity breath?
Case Study 5

A 28 year old woman delivered a 9.5 lb

infant .

The mothers history was incomplete

and she claimed to have had no

medical care through her pregnancy .

Shortly after birth the infant became

lethargic and flaccid.

Blood Glucose = 25 mg%
Ionized Calcium= 4.9 mg%
Questions

Give the possible explanation for the

infants large birth weight and size.

If the mother was gestational Diabetic

why was her baby hypoglycemic?

If the mother had been monitored

during pregnancy what laboratory tests

should have been performed?

Case Study 6
Laboratory tests were performed on a 50

year old lean white woman during an annual

physical examination . She has no family

history of Diabetes or any history of elevated

Glucose levels during Pregnancy.

Fasting Blood Glucose

90 mg%

Serum Cholesterol

140 mg%

HDL

40 mg%

Serum Triglycerides

90 mg%

Questions

What is probable

diagnosis of this patient?

Describe the proper

follow up for this patient?
Case Study 7

For 3 consecutive months, a fasting

Glucose and Glycosylated Hemoglobin

were performed on a patient. The result

are as follows:

Quarter 1 Quarter 2 Quarter 3

Fasting 280 mg%

85 mg%

91 mg%

Blood

Glucose

Hb A1c

7.8 %

15.3 %

8.5 %
Questions

In which quarter was the patients

Glucose the best regulated

Do the fasting Glucose and

Glycosylated Hb match? Why or

Why not?

Case Study 8
A 25 yr old healthy female

patient complains of dizziness

and shaking 1 hour after eating a

large heavy carbohydrate meal .

The result of random Glucose

test performed showed 55 mg%.

However he had lost

consciousness on that occasion;

his mother had made him drink

a heavily sugared milk thinking

that the child was feeling weak.

This seemed to have alleviated

symptoms.
Questions

Identify the characteristic of

Hypoglycemia in the case

study?

What tests should be

performed next to determine

the problem?

Case Study 9
A 5 year old child was brought to the

medical OPD in a comatose state . He

had felt headache and dizziness only a

few hours before. His father noticed

profuse sweating and some abnormal

behavior at that time and rushed him to

the hospital. A similar episode had

occurred two months earlier after the

child had a glass of sugarcane juice .

Presently physical examination

showed tachycardia and rapid

breathing . Liver was markedly

enlarged, being palpable 4 cm

below coastal margin .Blood

and urine samples were

analyzed .
Blood glucose was 52mg% , no

other abnormality was found in

the test result. The child was

given intravenous dextrose to

treat hypoglycemia. He

responded well and the

hypoglycemia symptoms were

promptly disappeared .

Two days later, Liver biopsy

reports revealed large

deposits of Fructose-1-PO4

within hepatocytes.
Questions

What is the probable biochemical defect

in this child ? Suggest a biochemical test

to evaluate the above diagnosis.

Provide biochemical explanation for the

child's sign and symptoms

Would you expect liver function to be

normal or sluggish in this child? Give

reason.

Suggest how to manage this condition?

Case Study 10
A 23 year old male developed fever

about two weeks back. He had

bouts of shivering temperature of

40. 4 degree centigrade and started

treatment with Primaquine after

identification of the parasites in a

blood smear.

The fever subsided the next day

the following symptoms

aggravated and he felt fatigue,

dizziness breathlessness on

slightest exertion headache and

insomnia and paresthesia of the

fingers and toes.
Three days later , the patient

noticed dark black coloured

urine. On examination he

showed pallor of the skin and

the mucous membrane, yellow

sclera . Jaundice, tachycardia(

heart rate 110/min) and systolic

murmurs were prominent and

spleen was enlarged.

Investigations

Patients

Reference

result

range

Hemoglobin

10.2 gm%

11-14 gm %

Reticulocyte

6.3 %

Up to 2 %

count

Serum Total

8.3 mg%

0.1 -1 mg %

Bilirubin

Urine bile

Absent

pigment
The red cells , on

microscopic examination ,

were found to contain small

inclusion bodies( Heinz

bodies).

Questions

What is the probable diagnosis?
What type of anemia and Jaundice

developed in patient?

State the biochemical basis of the

problem?

Which metabolic pathway is

affected in this disordered state?
Case Study 11

A premature infant of 2.3 kg body

weight, born to Diabetic mother,

was shifted to nursery after the

attending of paediatrician noticed .

The noted symptoms were muscle

twitching ,tremors profuse

sweating.
Soon after, the infant had

convulsions and lapsed into

comatose state. Blood analysis

showed .

Blood Glucose =38 mg%

Questions

What is the probable diagnosis?
Why there is muscle twitching in

infant?

Could the Diabetes in mother is

responsible for the infants

condition?

Why there is loss of consciousness?
THANKYOU

Quantitative Estimation Of

Blood Glucose
Glucose

Chemically Glucose is a Monosaccharide-
Aldo Hexose C6(H2O)6
Glucose is a chief sugar of body and blood.
It is a primary source of energy .
In blood the predominant form is D Glucose
Brain ,RBC's lens cells are totally dependent

on Glucose.

Main metabolic fates of Glucose is
To completely oxidize to liberate CO2 ,H2O and

ATP.

When Glucose is excess, it is converted to

Glycogen and Fat and stored as reservoir of

energy.

Blood Glucose is regulated by the hormonal

influence.

Insulin hormone lowers the blood Glucose.
Glucagon and Epinephrine increases blood

Glucose.
Aim Of An Experiment

Estimate the amount of

Glucose present in the given

test specimen

Col ection of Blood Sample

Intravenous blood is withdrawn
Collected in Tube containing Sodium

Fluoride(NaF) and Potassium Oxalate

(1:3 mixture)

NaF is antiglycolytic agent- Inhibits

Enolase of Glycolysis.

Potassium Oxalate- Anticoagulant.
Specimens used for Glucose

estimation:

?Whole blood
?Plasma
?Serum

Conditions Of blood Samples

Fasting Blood Sample (FBS):

qBlood sample collected in fasting condition after 10

-12 hrs of fast.

Post Prandial Blood Sample (PP Sugar):

vBlood sample collected after 2 hrs of meals.

Random Blood Sample (RBS):

? Blood sample collected any time.
Methods Used

True Glucose Method-Based on

Enzyme Use.

? GOD-POD Method
? Hexokinase

Based on Reducing Property Of Sugar.

vFolin Wu Method
vOrtho Toluidine Method

Principle Based On Reducing

Property

In hot and alkaline medium Glucose is

transformed to Enediol which reduces

the cupric ions to cuprous ions and

form the precipitate of Cuprous oxide.

Cuprous oxide then reduces

Phosphomolybdate to Molybdenum

blue.
The intensity of blue color

produced is directly

proportional to the amount of

reduction reaction brought by

reducing sugar.

The Optical Density of colored

solution is measured

calorimetrically.

A Glucose standard of 100

mg% is run similarly for

comparison and calculation of

unknown concentration of

Glucose present in test

specimen.
Methods based on reducing property of

sugar are not true glucose methods.

Actual Glucose concentration of blood

specimen cant be estimated out by

these methods.

In these methods other reducing

substances present in blood samples

also reduce and give the reaction.

Result values are higher than actual

Glucose concentration.

Principle Of GOD-POD Method
Glucose present in a test specimen is

acted upon by an enzyme Glucose

Oxidase (GOD) which oxidizes Glucose

to Gluconic acid and H2O2.

The enzyme Peroxidase (POD) then act

on H2O2 to liberate water and nascent

oxygen.

Nascent oxygen then reacts with a

chromogen 4-Aminoantipyrine to form

a pink color complex.

True Glucose Methods

The enzymatic based methods

for Glucose estimation are true

Glucose methods.

The enzyme specifically act on

Glucose and measure the

amount more accurately.
Protocol

S. No

Test

Standard

Blank

Distilled

1.8 ml

1.8 ml

2 ml

water

Plasma

0.2 ml

-------

--------

Glucose

-------

0.2 ml

--------

Standard

Glucose

3 ml

3 ml

3 ml

Reagent

Mix all the contents of the tube .
Incubate the tubes at 37 degree

centigrade for 15 minutes.

Read the O.D readings by

adjusting the filter to green (520

nm).

Record the O.D readings of Test,

Standard and Blank.
Calculation

Blood Glucose in mg% = O.D of T x 100

O.D of S

Results

The blood Glucose of

given test sample =

mg%
Clinical Interpretation

Normal Ranges

Fasting Blood Glucose= 70-110 mg%
Post Prandial Glucose = 110-140 mg%
Random Glucose = 80-140 mg %

Conditions Of Hyperglycemia

When estimated blood Glucose is above

the normal range it is hyperglycemia.

vDiabetes mellitus (Common Condition )

vStress, Anxiety , Anger , Fear
vHyper Thyroidism
vHyper Pituitarism
vHyper Adrenalism

Conditions Of Hypoglycemia

When the estimated blood Glucose is below

the normal range it is hypoglycemia.

qInsulin Over dose
qPancreatic Tumors (Insulinomas)
qProlonged Starvation
qHypo Adrenalism
qHypo Pituitarism
qHypo Thyroidism
Rol No's- Even No's

Observations
O.D of Test= 0.30
O.D of Standard= 0.28
Calculate Blood Glucose in mg%
Interpret your results.


Rol No's- Odd No's

Observations
O.D of Test= 0.60
O.D of Standard= 0.28
Calculate Blood Glucose in mg%
Interpret your results.



Thank You

This post was last modified on 05 April 2022