Which term best describes the overall process of converting glucose to energy in the presence of oxygen?

• A. Cellular respiration
• B. Fermentation
• C. Glycolysis
• D. Krebs cycle

Answer: (A)

Cellular respiration is the overall process by which cells convert glucose into usable energy in the presence of oxygen. It includes glycolysis in the cytoplasm, pyruvate oxidation to acetyl-CoA, the Krebs cycle, and the electron transport chain. Oxygen serves as the final electron acceptor at the end of the chain, allowing a large amount of ATP to be produced through oxidative phosphorylation. Most ATP comes from the electron transport chain, driven by NADH and FADH2 generated in the earlier steps, with water formed when electrons combine with oxygen.

Fermentation is the anaerobic alternative that cells can use when oxygen is scarce, producing far less ATP. Glycolysis is the initial stage that splits glucose into pyruvate and can occur without oxygen, but it is not the entire energy-making process. The Krebs cycle is a crucial middle step within cellular respiration, but by itself it doesn’t describe the full pathway. Since the question specifies energy production in the presence of oxygen, cellular respiration best fits.