Download MBBS Biochemistry PPT 65 Introduction To Metabolism Lecture Notes

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Metabolism

What is Metabolism?
? Metabolism is a network of metabolic /biochemical

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reactions.

? Carried out in living cells.
? In a well organized, integrated and regulated manner.

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? Related to various biomolecules viz

? Carbohydrates

? Lipids

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? Proteins

? Nucleoproteins

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?Metabolism involves

interconversions of chemical

compounds in the body.

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? Metabolite precursors are

transformed to end products via

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many specific intermediates.
?Metabolism is the sum of the

chemical changes that convert:

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?Nutrients into energy.

?Chemical y complex substances of

cel s into simpler forms.

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?Chemical y simple substances into

functional complex biomolecules.

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The Sun is Energy for Life

Phototrophs (Plants) use light to

drive synthesis of organic

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molecules.

Heterotrophs (Animals) use

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these as building blocks.

CO2,O2 and H2O are recycled.

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Importance Of Metabolism

?Normal Metabolism is vital for

health, growth, reproduction

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and good survival of human

beings.
Role of Enzymes and Hormones

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in Metabolism

?Enzymes along with Coenzymes

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biocatalyze specific metabolic

reactions.

?Thus Enzymes are "Functional

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units of Metabolism"
?Hormones are chemical

messengers of human body. They

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are regulators of Enzyme activity.

(Hormones Stimulate/Inhibit

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Enzyme activity)

?Enzyme reactions are

organized into discrete

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pathways.
Metabolite

?Metabolite is a substrate or a

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reactant undergoing a

biochemical/metabolic reaction.

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Metabolic Reaction

? Metabolic reaction is a biochemical

reaction where a metabolite is specifically

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reacted by an Enzyme and Coenzyme to

give a product.

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A E-Co B
Types Of Metabolic Reactions

? Reversible Reactions ? Same Enzyme is required.
? Not regulatory steps.

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E1

A E1 B

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? Irreversible Reactions-

?Different set of Enzyme required.

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?Non equilibrium Reactions.

?Regulatory steps.

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E2

C

D

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E3


Types Of

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Biochemical Reactions

? Oxidation/Dehydrogenation/Hy

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droxylation

? Reduction

? Hydrolytic

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? Carboxylation

? Decarboxylation
? Phosphorylation

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? Dephosphorylation

? Amination

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? Deamination

? Isomerization

? Hydration

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? Dehydration

Metabolic Pathway

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?Metabolic pathway is a series of wel

defined and significant biochemical

reactions followed one after another

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giving intermediate products and

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

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E1
B

E2

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

E3
D

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E4
E End Product of the pathway (E)

Organization of Pathways

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? Pathways consist of sequential steps.

? The enzymes may be separate.

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? May form a multienzyme complex.

? May be a membrane-bound system.

? New research indicates that multienzyme complexes

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are more common than once thought.


Mutienzyme complex

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Separate

enzymes

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Membrane

Bound System

Organization of Pathways

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Closed Loop

(intermediates recycled)

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Linear

Spiral

(product of rxns are

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(same set of

substrates for

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enzymes used

subsequent rxns)

repeatedly)

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Compartmentalization Of Metabolic

Pathways

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?Compartmentalization of

pathways permits

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integration and

regulation of metabolism.

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Phosphoryl-group Transfer

Types Of Metabolic Pathway

?Catabolic/Degradative /Energy

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Generating/ATP producing

Pathways/Exothermic.

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?Anabolic/Synthetic/Energy Utilizing/

ATP Using Pathways/Endothermic.
?Catabolic pathways involve

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oxidative reactions producing

reducing equivalents- NADH+H+

and FADH2.

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?Catabolic pathways converge to

few end products.

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?Anabolic pathways

diverge to synthesize

many biomolecules.

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? .

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?Some pathways serve both in

catabolism and anabolism ,those

are Amphibolic pathways.

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?Amphibolic Pathways occur at the

crossroads of metabolism.

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?Amphibolic pathways links between

Anabolic and Catabolic pathways.
Regulation of Metabolic

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Pathways

?Regulation means stimulation and

inhibition of pathways as per cellular

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need.

?Hormones regulate the metabolic

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pathways.

?Metabolic pathways are regulated to

allow the organism to respond to

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changing conditions.
?Every metabolic pathway has its

specific regulatory enzymes/key

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enzymes.

?Hormones regulate by either

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stimulating /inhibiting the

regulatory/key enzymes of the

pathway.

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Modes Of Metabolic Regulation

? Al osteric regulation
? Covalent modification

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? Control of enzyme levels
? Compartmentalization
? Metabolic specialization of organs

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?Feedback inhibition ? product

of pathway down regulates

activity of early step in

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pathway

?Feedforward activation ?

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metabolite produced early in

pathway activates down stream

enzyme

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Regulating Related Catabolic

? Anab a

oli n

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c d

&

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cA

atn

a a

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bob

li o

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c l

p iac

t

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h Pa

waytsh

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w

invoa

lvy

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insg the

same compounds are not the same.

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? Some steps may be common to both

? Others must be different - to ensure that each

pathway is spontaneous.

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? This also al ows regulation mechanisms to turn

one pathway onn and the other off.

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Modes Of Enzymes Regulation

?Alteration in membrane permeability.

?Conversion of Inactive to Active form.

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?Stimulation of mRNA translation.

?Induction of new mRNA formation.

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?Repression of mRNA formation.
?Knowledge of normal metabolism

is essential for :

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?Understanding adaptations of

?Starvation

?Exercise

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?Pregnancy and lactation.

?Understanding of metabolic

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disorders.

Abnormal Metabolism Is Due To

vNutritional Deficiencies

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vEnzyme Defects
vHormonal Defects
vDrug and Toxin Interactions
?Normal Enzyme and Hormonal

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activities gives normal

metabolism and health to

human body.

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?Defect in Enzymes and

Hormones derange the normal

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metabolism.

Derangement in Metabolism

?Any defect or derangement in normal pattern of

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metabolism leads to metabolic disorders.

?Mutation in Genes of Enzymes, forms defective

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Enzymes.

?Congenital defect of Enzyme leads to Inborn

Error Of Metabolism.

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Inborn Error Of Metabolism

?Congenital deficiency of any

single Enzyme of a metabolic

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pathway leads to Inborn

Errors of Metabolism.

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Enzyme Deficiency of a

Metabolic Pathway

? Blocks the metabolic reaction.

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? Blocks the metabolic pathway.

? Accumulates and excrete intermediate

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product of the pathway.

? No formation of end product of the

pathway.

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? Affects other interrelated metabolic

pathways.
Methods Used to Study Metabolism

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? Metabolic Reactions/Metabolic

Pathways were studied :

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?Using whole organism/Cel ular

fractions

?Using Metabolic Probes.

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?Using Radioisotopes.