AP BIOLOGY

Detailed explanation-1: -In the second reaction of the Krebs cycle, the isomerisation of citrate to isocitrate takes place. As an intermediate, cis-aconitate is formed. Therefore, it is a two-step reaction sequence.

Detailed explanation-2: -Step 3. Isocitrate is converted into -ketoglutarate in a reaction catalyzed by isocitrate dehydrogenase. An NAD+ molecule is reduced to NADH + H+ in this reaction, and a carbon dioxide molecule is released as a product.

Detailed explanation-3: -Step four of the Krebs Cycle: -Ketoglutarate Dehydrogenase Figure: Formation of succinyl-CoA In the fourth reaction of the citric acid cycle, an oxidative decarboxylation takes place. This means that again a CO2 molecule is relased (decarboxylation) and that an odixation takes place.

Detailed explanation-4: -Step 5 of the Krebs cycle: Succinyl-CoA Synthetase The reaction of succinyl-CoA to succinate (see figure) proceeds via the intermediate succinyl phosphate. In the first step, the coenzyme A (green), which is located at the succinyl group, is substituted by a hydrogen phosphate ion (yellow).