Which energy carriers are produced by the Krebs cycle?

Which energy carriers are produced by the Krebs cycle?

• A. NADH and FADH2
• B. ATP only
• C. CO2 only
• D. Pyruvate

Answer: (A)

The main idea is that the Krebs cycle generates reduced electron carriers that feed the respiratory chain. As acetyl-CoA is oxidized, electrons are removed and handed to NAD+, forming NADH, and at the succinate to fumarate step, FAD accepts electrons to form FADH2. These carriers carry high-energy electrons to the electron transport chain, where their energy drives ATP production. The cycle also releases CO2 as a byproduct, and pyruvate is the starting substrate that becomes acetyl-CoA before entering the cycle, not a product of the cycle. There is a small amount of ATP produced directly in one step, but the principal energy carriers produced are NADH and FADH2.

The main idea is that the Krebs cycle generates reduced electron carriers that feed the respiratory chain. As acetyl-CoA is oxidized, electrons are removed and handed to NAD+, forming NADH, and at the succinate to fumarate step, FAD accepts electrons to form FADH2. These carriers carry high-energy electrons to the electron transport chain, where their energy drives ATP production. The cycle also releases CO2 as a byproduct, and pyruvate is the starting substrate that becomes acetyl-CoA before entering the cycle, not a product of the cycle. There is a small amount of ATP produced directly in one step, but the principal energy carriers produced are NADH and FADH2.