Download MBBS (Bachelor of Medicine, Bachelor of Surgery) 1st year (First Year) Biochemistry ppt lectures Topic 48 Carbohydrate Metabolism Notes. - biochemistry notes pdf, biochemistry mbbs 1st year notes pdf, biochemistry mbbs notes pdf, biochemistry lecture notes, paramedical biochemistry notes, medical biochemistry pdf, biochemistry lecture notes 2022 ppt, biochemistry pdf.
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