[php snippet=1]
At what enzymatic step in the citric acid cycle (Krebs cycle) does substrate level phosphorylation occur?

Loading ...
Correct Answer: B. Succinyl coenzyme A to succinate
There is only one step in the citric acid cycle that causes substrate level phosphorylation: the conversion of succinyl coenzyme A to succinate. GDP and inorganic phosphate combine to form GTP, which is roughly equivalent to the formation of one molecule of ATP. All others do not produce ATP. Oxaloacetate may be formed from pyruvate though it requires the dephosphorylation of one molecule of ATP. Moreover, this reaction is not considered one of the classic reactions in the citric acid cycle. In the conversion of malate to oxaloacetate, NAD+ loses a proton to form NADH.
Get it right? Tweet at us:
Subscribe below to receive the MCAT Question of the Day delivered straight to your inbox every morning.