In the process of cellular respiration in a healthy person, what is the primary role of oxygen in the body?

• A. It acts as the final electron acceptor in the electron transport chain, forming water.
• B. It breaks down pyruvate into carbon dioxide in the cytoplasm.
• C. It is used to synthesize ATP directly in the Krebs cycle.
• D. It is converted directly into glucose during glycolysis.

Answer: (A)

Verified step by step guidance

1. Understand the context of cellular respiration: Cellular respiration is the process by which cells generate energy (ATP) by breaking down glucose. It consists of three main stages: glycolysis, the Krebs cycle, and the electron transport chain.
2. Identify the role of oxygen in cellular respiration: Oxygen is involved in the electron transport chain, which is the final stage of cellular respiration. It does not directly participate in glycolysis or the Krebs cycle.
3. Explain the electron transport chain: During this stage, electrons are transferred through a series of protein complexes embedded in the inner mitochondrial membrane. These electrons are derived from NADH and FADH₂ produced in earlier stages of cellular respiration.
4. Clarify the role of oxygen as the final electron acceptor: At the end of the electron transport chain, oxygen accepts electrons and combines with protons (H⁺) to form water (H₂O). This step is crucial for maintaining the flow of electrons and preventing a backup in the chain.
5. Eliminate incorrect options: Oxygen does not break down pyruvate (this occurs in the Krebs cycle), synthesize ATP directly (ATP is synthesized via oxidative phosphorylation), or convert into glucose during glycolysis (glycolysis breaks down glucose into pyruvate). The correct role of oxygen is as the final electron acceptor in the electron transport chain.