Principles of Biochemistry 4e

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• Chapter 13. The citric acid cycle.
• Introduction
• The mitochondrion
• Conversion of pyruvate to acetyl CoA

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1. Introduction
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1. Intrroduction
Glucose (6C) 6 O2 ? 6 CO2 6 H2O
Energy
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1. Introduction where are we?
Glucose (6C) 2 Pyruvate (3C)
2NADH 2ATP
2NAD
2NAD
2 Ethanol 2CO2
2 Lactate
2CO2
2 NADH
2 Acetyl CoA
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2 Acetyl CoA (2C)
Citric acid cycle
4 CO2
6 NADH
6 FADH2
2 GTP
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• The mitochondrion power house
• of the cell

Cytosol- glycolysis
Citric acid cycle
Inter membrane space
Electron transport ATP formation
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C F
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3. Conversion of pyruvate to acetyl CoA
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Pyruvate dehydrogenase complex E1 pyruvate
dehydrogenase thiamine pyrophosphate E2 Dihydr
olipoamide acetyltransferase lipoic
acid E3 Dihydrolipoamide dehydrogenase FAD
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Also mobile cofactors CoA NAD
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E1 pyruvate dehydrogenase thiamine
pyrophosphate
carbanion
Thiamine pyrophosphate
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Step 1 E1 - decarboxylation
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Step 2 E2
Redox rx.
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Step 3 E2 Transfer acetate to CoA.
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Step 4. E2 Reoxidation of lipoamide by FAD
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Step 5 E3 Reoxidation of FADH2 by NAD
FADH2 NAD ?? FAD NADH
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Acetyl-CoA is a crossroads.
fats
glycogen
Fatty acids
Amino acids
glucose
Acetyl-CoA
biosynthesis
Citric acid cycle
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Produces FADH2
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Very important
pyruvate
CO2
CoA
NADH
Acetyl-CoA
CoA
citrate
oxaloacetate
NADH
isocitrate
CO2
malate
NADH
a-ketoglutarate
fumerate
CoA
CO2
NADH
succinate
FADH2
Succinyl-CoA
GTP
CoA
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