Chapter 16 Citric acid cycle II

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Chapter 16 Citric acid cycle -II
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The Citric Acid Cycle
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Regulation of the Citric Acid Cycle
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Control of Pyruvate Dehydrogenase
Inhibited by ATP, acetyl CoA and NADH Activated
by ADP
High ATP?kinase activated?
PDH is phosphorylated? inactive
Low ATP? phosphatase activated? phosphate
removed?activated
Acetyl-CoA inhibits. When fats are plentiful
they are burned producing acetyl-CoA and you
dont need any more.
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Table 16.3 Active and Resting Cells

• Cells in a resting metabolic state
• need and use comparatively little energy
• high ATP, low ADP imply high ATP/ADP ratio
• high NADH, low NAD imply high NAHDH/NAD ratio

• Cells in an active metabolic state
• need and use more energy than resting cells
• low ATP, high ADP imply low ATP/ADP ratio
• low NADH, high NAD imply low NAHDH/NAD ratio

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Is it possible to synthesize carbohydrates from
acetyl-CoA?
Animals No
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Plants and some bacteria yes
Glyoxylate pathway
Bypass the 2 CO2 Releasing Sites.
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The citric acid cycle is also involved in
catabolism.
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Replenishing oxaloacetate
Mammals can not.
Plants can do this Mammals can not.
Pyruvate kinase