Fate of pyruvate under aerobic conditions — After glycolysis, when oxygen is available as the terminal electron acceptor, which process predominates?

Introduction / Context:
Glycolysis yields pyruvate, ATP, and NADH. The cell’s next steps depend on oxygen availability. Under aerobic conditions, mitochondria oxidize reduced cofactors to drive ATP formation via oxidative phosphorylation, rather than regenerating NAD+ through fermentation.

Given Data / Assumptions:

• Oxygen is present to act as the final electron acceptor.
• Glycolysis has already produced pyruvate and NADH.
• Choice is among processes occurring after glycolysis.

Concept / Approach:
With oxygen, pyruvate is converted to acetyl-CoA, enters the TCA cycle, and generates more NADH and FADH2. These reduced cofactors feed the ETC, producing a proton motive force used by ATP synthase. The defining aerobic step is oxidative phosphorylation, which captures free energy from electron transfer to synthesize ATP.

Step-by-Step Solution:

Verification / Alternative check:
Measured oxygen consumption aligns with ATP yields far exceeding fermentation, confirming that oxidative phosphorylation predominates when O2 is available.

Why Other Options Are Wrong:

• “Pyruvate is formed” and “NADH is produced” describe glycolysis itself, not what follows.
• Fermentation occurs when O2 is absent, to reoxidize NADH to NAD+.

Common Pitfalls:
Equating “aerobic” solely with the TCA cycle; the defining ATP-yielding process is oxidative phosphorylation in the mitochondrion.

Final Answer:
Oxidative phosphorylation