Question

Reduced coenzyme FADH$_2$ is formed between which of the following intermediates in Krebs cycle?

• A. Isocitrate and oxalosuccinate
• B. Succinate and fumarate
• C. Malate and oxaloacetate
• D. Fumarate and malate

Hint:

Succinate dehydrogenase is the only Krebs cycle enzyme embedded in inner mitochondrial membrane.

Answer 1

The Correct Option is B

Step 1: Understanding role of FAD.
FAD acts as a hydrogen acceptor during certain steps of the Krebs cycle.
Step 2: Specific reaction.
Succinate is oxidized to fumarate by the enzyme succinate dehydrogenase.
Step 3: Formation of FADH$_2$.
During this oxidation, FAD is reduced to FADH$_2$.
Step 4: Conclusion.
Hence, FADH$_2$ is formed between succinate and fumarate.