Name the three main stages of aerobic respiration.

Name the three main stages of aerobic respiration.

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

Answer: (D)

The main idea here is the sequence of stages that accomplishes energy production under aerobic conditions: glycolysis, the Krebs cycle, and the electron transport chain. In glycolysis, glucose is split in the cytosol to form two pyruvate molecules, yielding a net 2 ATP and 2 NADH. The pyruvate then enters the mitochondria and is converted to acetyl‑CoA, which feeds the Krebs cycle. There, acetyl‑CoA is oxidized to CO2, while transferring energy to NADH and FADH2 and producing a small amount of direct ATP. The NADH and FADH2 then power the electron transport chain on the inner mitochondrial membrane, where electrons moving through the chain drive proton pumps to create a gradient. This gradient powers ATP synthase to generate the bulk of ATP, with oxygen serving as the final electron acceptor to form water. Fermentation isn’t part of aerobic respiration, and photosynthesis is a separate process, so this sequence uniquely fits the three main stages.

The main idea here is the sequence of stages that accomplishes energy production under aerobic conditions: glycolysis, the Krebs cycle, and the electron transport chain. In glycolysis, glucose is split in the cytosol to form two pyruvate molecules, yielding a net 2 ATP and 2 NADH. The pyruvate then enters the mitochondria and is converted to acetyl‑CoA, which feeds the Krebs cycle. There, acetyl‑CoA is oxidized to CO2, while transferring energy to NADH and FADH2 and producing a small amount of direct ATP. The NADH and FADH2 then power the electron transport chain on the inner mitochondrial membrane, where electrons moving through the chain drive proton pumps to create a gradient. This gradient powers ATP synthase to generate the bulk of ATP, with oxygen serving as the final electron acceptor to form water. Fermentation isn’t part of aerobic respiration, and photosynthesis is a separate process, so this sequence uniquely fits the three main stages.