Which process is the second stage of cellular respiration, breaking down pyruvic acid into carbon dioxide?

Which process is the second stage of cellular respiration, breaking down pyruvic acid into carbon dioxide?

• A. Glycolysis
• B. Electron transport chain
• C. Krebs cycle
• D. Fermentation

Answer: (C)

The main idea is the stage where the carbon atoms from the initial sugar are fully oxidized and energy carriers are produced to power the rest of cellular respiration. The Krebs cycle is the second major stage because it takes the acetyl group from acetyl-CoA and oxidizes it step by step, releasing carbon dioxide and generating NADH and FADH2 that feed the electron transport chain. While the initial glycolysis step breaks glucose into pyruvate in the cytoplasm, and the electron transport chain is the final stage that uses the NADH and FADH2 to make most of the ATP, the Krebs cycle is the key phase where the carbon backbone is released as CO2 and energy-rich carriers are produced to drive later steps. (Note: the conversion of pyruvate to acetyl-CoA with CO2 release happens just before the cycle, linking glycolysis to this stage.)

The main idea is the stage where the carbon atoms from the initial sugar are fully oxidized and energy carriers are produced to power the rest of cellular respiration. The Krebs cycle is the second major stage because it takes the acetyl group from acetyl-CoA and oxidizes it step by step, releasing carbon dioxide and generating NADH and FADH2 that feed the electron transport chain. While the initial glycolysis step breaks glucose into pyruvate in the cytoplasm, and the electron transport chain is the final stage that uses the NADH and FADH2 to make most of the ATP, the Krebs cycle is the key phase where the carbon backbone is released as CO2 and energy-rich carriers are produced to drive later steps. (Note: the conversion of pyruvate to acetyl-CoA with CO2 release happens just before the cycle, linking glycolysis to this stage.)