BIOCHEM FINAL - TCA cycle

Isocitrate dehydrogenase

what enzyme catalyzes the first decarboxylation in the TCA cycle?

it forms a a β-keto intermediate that decarboxylates in a Mn²⁺-dependent reaction.

how does isocitrate dehydrogenase enable decarboxylation?

α-ketoglutarate dehydrogenase.

what enzymes catalyzes the second decarboxylation in the TCA cycle?

By forming a high-energy thioester bond in succinyl-CoA.

How does α-ketoglutarate dehydrogenase conserve energy

No, they come from carbons already in the cycle

do the two CO2 carbons released come from the acetyl-CoA carbons that entered?

remaining carbons are more reduced

why can more energy still be harvested from TCA intermediates after decarboxylation?

GTP, using the high-enregy thioester bond of succinyl-CoA (substrate-level phosphorylation)

What does succinyl-CoA synthetase produce, and how?

Oxidation of succinate to fumarate (alkane → alkene) yields less energy, not enough to reduce NAD⁺.

why does succinate dehydrogenase use FAD instead of NAD+?

Malate → oxaloacetate, producing NADH

what reaction does malate dehydrogenase catalyze?

3 NADH, 1 FADH₂, and 1 GTP (10 ATP equivalent).

what is produced per acetyl-CoA in the TCA cycle?

about 32 ATP per glucose

how much ATP is made from glucose using glycolysis + TCA cycle + oxidative phosphorylation?

to fully oxidize acetate efficiently without directly oxidizing a CH3 group

how does the TCA cycle use 8 sequential steps?

amino acids, hemes, nucleobases, sugars

what are some biomolecules made from TCA cycle intermediates?

replenish TCA intermediates removed from biosynthesis

what do anaplerotic reactions do?

Pyruvate + bicarbonate → oxaloacetate

what is the main anaplerotic reaction?