Term
| Identify where in the cell pyruvate, fatty acids and acetyl-CoA are oxidized |
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Definition
Pyruvate->acetyl CoA: mitochondria
Fatty acids: mitochondria
Acetyl CoA (TCA cycle): mitochondria |
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Term
| Describe the relationship between the oxidation of pyruvate the formation of acetyl-CoA and teh generation of NADH and FADH2 |
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Definition
Pyruvate oxidation->Acetyl CoA: generates NADH
TCA cycle: generates 3NADH, 1 FADH2
These must be regenerated for the electron transfer chain within the mitochondria |
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Term
Identify the following steps in the citric acid cycle
1) Initial reaction in which citrate is formed
2) Steps that generate reduced cofactors (NADH, FADH2)
3) Step in which high energy GTP is formed |
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Definition
1) Initial reaction in which citrate is formed:
Citrate synthase: Acetyl-CoA + oxaloacetate -> Citrate + CoASH
2) Steps that generate reduced cofactors (NADH, FADH2)
Isocitrate dehydrogenase: NAD+ + Isocitrate -> α-ketoglutarate + NADH
a-ketoglutarate dehydrogenase: NAD+ + CoASH + α-ketoglutarate -> NADH + Succinyl CoA
Succinate dehydrogenase: succinate + FAD -> Fumerate +FADH2
3) Step in which high energy GTP is formed
SuccinylCoA Synthase: Succinyl CoA + GDP -> Succinate + GTP |
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Term
| Identify the biosynthetic pathways for which citric acid cycle intermediates serve as precursors or intermediates |
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Definition
Citrate: Fatty acid and sterol synthesis
α-ketoglutarate: amino acid synthesis
Succinyl CoA -> hemesynthesis
Malate -> Gluconeogenesis
Oxaloacetate -> Amino Acid synthesis |
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Term
| Explain how citric acid cycle intermediates are replenished |
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Definition
Amino acids -> Pyruvate
Glutamate: α-ketoglutarate
Aspartate: Oxaloacetate or fumerate
Valine and isoleucine: proponyl CoA -> succinyl CoA
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Term
| Identify the key regulatory enzymres of the TCA cyle and their allosteric activators and inhibitors |
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Definition
1) Isocitrate Dehydrogenase:
Activated by: ADP
Inhibited by: NADH, ATP
2) α-ketoglutarate dehydrogenase:
Activated by: Ca2+
Inhibited by: ATP, GTP, NADH
3) Citrate synthase:
Inhibited by: succinyl CoA |
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Term
| Explain how the inhibition of one or more regulatory enzyme would affect the oxidation of acetyl-CoA, ATP production, fatty acid biosynthesis |
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Definition
Oxidation of acetyl CoA: Decreased
ATP production: Decreased
Fatty acid biosynthesis: decreased (due to decreased citrate) |
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Term
| Explain how levels of ADP, PO4 and O2 might exert a "course control" on the activity of the TCA cycle |
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Definition
ADP - allosteric activator of isocitrate dehydrogenase
PO4 - substrated needed to make GTP via succinyl CoA synthase
O2 - needed as end product of electron transfer chain, required for generation of NAD+ and FADH, which are needed in four steps of CTA total. |
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