What is the role of oxygen in cellular respiration?

• A. It provides energy directly to ATP synthase.
• B. It acts as the final electron acceptor in the electron transport chain.
• C. It breaks down glucose during glycolysis.
• D. It is converted into glucose during the Krebs cycle.

Answer: (B)

Verified step by step guidance

1. Understand the process of cellular respiration: Cellular respiration is the process by which cells generate energy in the form of ATP by breaking down glucose. It consists of three main stages: glycolysis, the Krebs cycle, and the electron transport chain.
2. Focus on the electron transport chain: This is the final stage of cellular respiration, where most ATP is produced. Electrons are transferred through a series of protein complexes embedded in the inner mitochondrial membrane.
3. Identify the role of oxygen: Oxygen acts as the final electron acceptor in the electron transport chain. It combines with electrons and protons to form water, which is essential for maintaining the flow of electrons and preventing a backup in the chain.
4. Clarify why oxygen does not directly provide energy to ATP synthase: ATP synthase generates ATP using the proton gradient created by the electron transport chain. Oxygen's role is to ensure the chain continues functioning, indirectly supporting ATP production.
5. Eliminate incorrect options: Oxygen does not break down glucose (glycolysis does this), nor is it converted into glucose during the Krebs cycle. Its primary role is as the final electron acceptor in the electron transport chain.