Molecular oxygen (\(O_2\)) has what role in aerobic cellular respiration?

• A. It acts as the final electron acceptor in the electron transport chain.
• B. It is used to break down glucose during glycolysis.
• C. It donates electrons to NADH during the Krebs cycle.
• D. It is converted directly into ATP during oxidative phosphorylation.

Answer: (A)

Verified step by step guidance

1. Understand the process of aerobic cellular respiration, which includes glycolysis, the Krebs cycle, and oxidative phosphorylation. Molecular oxygen (\(O_2\)) plays a critical role in the final stage, oxidative phosphorylation.
2. Learn about the electron transport chain (ETC), where electrons are transferred through a series of protein complexes embedded in the inner mitochondrial membrane. This process generates a proton gradient used to produce ATP.
3. Recognize that molecular oxygen (\(O_2\)) acts as the final electron acceptor in the electron transport chain. It combines with electrons and protons to form water (\(H_2O\)), ensuring the continuation of the ETC.
4. Clarify that \(O_2\) is not directly involved in glycolysis, as glycolysis occurs in the cytoplasm and does not require oxygen. It is also not converted directly into ATP during oxidative phosphorylation; instead, ATP is synthesized by ATP synthase using the proton gradient.
5. Understand that \(O_2\) does not donate electrons to NADH during the Krebs cycle. NADH is produced during the Krebs cycle and donates electrons to the electron transport chain, where \(O_2\) accepts them at the end.