In cellular respiration, which molecule is the final electron acceptor in the electron transport chain?

• A. Carbon dioxide (\(CO_2\))
• B. Oxygen (\(O_2\))
• C. NADH
• D. Glucose (\(C_6H_{12}O_6\))

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the concept of the electron transport chain (ETC) in cellular respiration. The ETC is the final stage of cellular respiration, where electrons are transferred through a series of protein complexes embedded in the inner mitochondrial membrane.
2. Step 2: Recall that the purpose of the ETC is to create a proton gradient by transferring electrons from electron carriers (like NADH and FADH2) to the complexes, ultimately driving ATP synthesis.
3. Step 3: Identify the role of the final electron acceptor. The ETC requires a molecule to accept electrons at the end of the chain to prevent the system from stalling. This molecule is reduced in the process.
4. Step 4: Analyze the options provided: Carbon dioxide (\(CO_2\)) is a waste product of cellular respiration, not involved in the ETC; NADH is an electron donor, not an acceptor; Glucose (\(C_6H_{12}O_6\)) is the initial substrate for glycolysis, not part of the ETC.
5. Step 5: Recognize that Oxygen (\(O_2\)) is the correct answer. It acts as the final electron acceptor in the ETC, combining with electrons and protons to form water (\(H_2O\)), which is a byproduct of cellular respiration.