Under hypoxic conditions, why do cells rely on glycolysis for energy production?

Under hypoxic conditions, why do cells rely on glycolysis for energy production?

• A. Because glycolysis yields more ATP than oxidative phosphorylation.
• B. Because oxygen is abundant for oxidative phosphorylation.
• C. Because oxygen is limited and cannot support oxidative phosphorylation.
• D. Because glycolysis requires oxygen to proceed.

Answer: (C)

When oxygen is limited, cells rely on glycolysis because oxidative phosphorylation cannot operate without a sufficient oxygen supply to accept electrons in the electron transport chain. Without oxygen, the chain stalls and NADH cannot be reoxidized to NAD+, which would halt glycolysis too. Glycolysis, performed in the cytoplasm, can proceed without oxygen and provides ATP, though only about 2 ATP per glucose, so it serves as a quicker, low-oxygen source of energy until oxygen becomes available again. The other statements aren’t accurate: oxidative phosphorylation needs oxygen, glycolysis does not require oxygen, and glycolysis does not produce more ATP than oxidative phosphorylation.

When oxygen is limited, cells rely on glycolysis because oxidative phosphorylation cannot operate without a sufficient oxygen supply to accept electrons in the electron transport chain. Without oxygen, the chain stalls and NADH cannot be reoxidized to NAD+, which would halt glycolysis too. Glycolysis, performed in the cytoplasm, can proceed without oxygen and provides ATP, though only about 2 ATP per glucose, so it serves as a quicker, low-oxygen source of energy until oxygen becomes available again. The other statements aren’t accurate: oxidative phosphorylation needs oxygen, glycolysis does not require oxygen, and glycolysis does not produce more ATP than oxidative phosphorylation.