What is the Krebs cycle?

• A. Photosynthesis
• B. Process that converts acetyl CoA to carbon dioxide in the mitochondria
• C. Production of ATP in cytoplasm
• D. Breakdown of fatty acids

Answer: (B)

Krebs cycle is the mitochondrial, aerobic process that fully oxidizes acetyl-CoA to carbon dioxide, while capturing high-energy electrons in NADH and FADH2 and producing a small amount of ATP directly. The cycle starts when acetyl-CoA joins with oxaloacetate to form citrate, then a series of enzyme-driven steps regenerates oxaloacetate for another turn. The NADH and FADH2 produced feed the electron transport chain, where most of the ATP is generated.

Photosynthesis occurs in chloroplasts and uses light to build sugars, not the Krebs cycle. Producing ATP in the cytoplasm describes glycolysis, which happens in the cytosol and yields ATP before the mitochondria are involved. Breakdown of fatty acids refers to beta-oxidation, which provides acetyl-CoA for the cycle but is a separate process from the cycle itself.