During cellular respiration, the oxygen consumed is directly involved in which of the following processes?

• A. Accepting electrons at the end of the electron transport chain
• B. Forming ATP in the cytoplasm
• C. Breaking down glucose during glycolysis
• D. Phosphorylating ADP to ATP during substrate-level phosphorylation

Answer: (A)

Verified step by step guidance

1. Understand the process of cellular respiration: Cellular respiration is a metabolic pathway that converts glucose into energy (ATP) through glycolysis, the citric acid cycle, and the electron transport chain. Oxygen plays a critical role in the final stage of this process.
2. Review the role of oxygen in the electron transport chain: Oxygen acts as the final electron acceptor in the electron transport chain, which occurs in the inner mitochondrial membrane. This is essential for the chain to continue functioning and for ATP production.
3. Eliminate incorrect options: Forming ATP in the cytoplasm occurs during glycolysis, which does not require oxygen. Breaking down glucose during glycolysis is an anaerobic process, meaning it does not involve oxygen. Phosphorylating ADP to ATP during substrate-level phosphorylation happens in glycolysis and the citric acid cycle, and does not directly involve oxygen.
4. Focus on the correct process: Oxygen is consumed during the electron transport chain, where it accepts electrons and combines with protons to form water. This step is crucial for maintaining the flow of electrons and enabling ATP synthesis via oxidative phosphorylation.
5. Conclude the reasoning: Based on the above analysis, oxygen's role in cellular respiration is specifically tied to accepting electrons at the end of the electron transport chain, ensuring the continuation of the process and efficient ATP production.