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Bioenergetics and Introduction to

Metabolism -2The transfer and utilization of energy in biologic systems

Faisal Khatib MD; PhD

Faculty of Medicine, University of Jordan

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Other nucleotide triphosphates

• GTP, UTP, CTP

• Synthesized from ATP

ATP + GDP ADP + GTP

– GTP in protein synthesis

– UTP in polysaccharide synthesis

– CTP in phospholipids synthesis

UDP- is a carrier of activated sugar

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UDP-glucose in glycogen synthesis

• Glycogen synthesis from glucose requires

energy

– Glucose Glycogen + H2O

• UDP-glucose is the activated carrier of glucose

UTP + Glucose 1-P UDP-Glc + PPi

UDP-Glc + Glycogen(n) UDP + Glycogen(n+1)

Acetyl Coenzyme A is a high energy

compound

• Coenzyme A is a universal carrier of Acyl groups

• Forms thioester bond with carboxyl group

O O װ װ

• RC~S-CoA CH3C~S-CoA

Acyl CoA Acetyl CoA

Acetyl CoA + H2O Acetate + CoA ∆Gº = -7.5kcal

Acetylcholine + H2O Acetate + Choline ∆Gº = -3 kcal

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Adenine

Ribose

2

phosphates

Pantothenic acid

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Coenzyme A is a donor of Acyl groups

Acetate + Choline Acetylcholine + H2O ∆Gº = +3 kcal

Acetyl CoA + H2O Acetate + CoA ∆Gº = -7.5kcal

Acetyl CoA + Choline Acetylcholine + COA

Oxidation of fuel molecules occurs in

two stages• Oxidation: Loss of electrons

• Reduction: Gain of electrons

• Aerobic oxidation: Transfer of electrons to

oxygen

- 1st stage: Transfer of e to electron carrier

- 2nd stage: Transfer of e to oxygen

Fuel � electron carrier � Oxygen

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A•• A

Carrier carrier••

O•• O

ADP + PiATP

Electron carriers• Electron carriers are dinucleotides

• Nucleotide is formed from

Phosphate- ribose- Nitrogenous base

• Two nucleotides connected through phosphate � Dinucleotide

• One of the bases is Adenine

• NAD+: Nicotinamide Adenine Dinucleotide

• FAD: Flavin Adenine Dinucleotid

Base Ribose

P PRibose

Adenine

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Reduction potential

• A- + B A + B-

Type of reaction

What determine the direction of the reaction?

• A+ + B+++ A++ + B++

Type of reaction

What determine the direction of the reaction?

P P

Reduction potential and direction of the

reaction

A + B- A- + B ∆Gº = -ve

B oxidized form

B- reduced form

A

A-

B

B-

V

Redox couple

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Reduction potential and direction of the

reaction

H+ + X- H2 + X ∆Gº = -ve

X oxidized form

X- reduced form

X

X-

H+

V

Redox couple

H2

X- has higher

tendency to loose

electrons than H2

does

�

Negative reduction

potential

Reduction potential: Ability to accept electrons

- 0.19LactatePyruvate

+ 0.82wateroxygen

+ 0.22Cytochrome+2Cytochrome+3

+ 0.03SuccinateFumarate

- 0.20EthanolAcetaldehyde

- 0.32NADHNAD+

- 0.60AcetaldehydeAcetate

- 0.67α ketoglutarateSuccinate

∆Eº�ReducedOxidized + e-

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Calculation of ∆Gº from ∆Eº

• ∆Gº = - nF ∆Eº

– F = Farady constant = 23.06 kcal/ Volt

• Calculate ∆Gº of the following reaction

NADH + 1/2O2 NAD+ + H2O

NADH NAD+ + 2e- ∆Eº = +0.32

O + 2e- O2- ∆Eº = +0.82

∆Gº = - 52.6 kcal/mol

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Degradation and synthesis occur in

a stepwise manner

A G

Not a single step but a sequence of steps

A B C D E F G

Called metabolic pathway

Anabolic or Catabolic