Question

About citric acid cycle, which statement is WRONG?

A. The enzymes involved are localized in the mitochondrial matrix except succinate dehydrogenase
B. No O2 is required for the citric acid cycle
C. It is a shared pathway for the catabolism of glucose and fatty acids
D. No substrate level phosphorylation happens throughout the cycle

Answer 1

The incorrect statement is D, as substrate-level phosphorylation does occur once in the citric acid cycle, producing one ATP or GTP per cycle. Statements A, B, and C are correct descriptions of the cycle.

Step-by-step explanation:

The incorrect statement about the citric acid cycle is: D. No substrate level phosphorylation happens throughout the cycle. In fact, there is one instance of substrate-level phosphorylation during the cycle, where one molecule of GTP or ATP is produced directly. This occurs in the conversion of succinyl-CoA to succinate.

The other statements are correct: A) The enzymes of the citric acid cycle are localized in the mitochondrial matrix except succinate dehydrogenase, which is found in the inner mitochondrial membrane.

B) The cycle itself does not require oxygen directly, but it is considered part of aerobic metabolism because the NADH and FADH₂ produced must transfer electrons to the next pathway that uses oxygen. C) It serves as a shared pathway for the catabolism of carbohydrates (via glucose) and fatty acids.