Which process describes energy production in the absence of oxygen?

Which process describes energy production in the absence of oxygen?

• A. Aerobic metabolism
• B. Fermentation
• C. Anaerobic metabolism
• D. Photosynthesis

Answer: (C)

When oxygen isn’t available, cells rely on anaerobic metabolism to make energy. Without oxygen, the electron transport chain can’t operate, so cells must regenerate NAD+ to keep glycolysis going and produce ATP through anaerobic pathways. Fermentation is a common example of these pathways, converting pyruvate into lactate or ethanol and CO2 to allow glycolysis to continue, but anaerobic metabolism is the broader term that covers all energy-producing processes that don’t require oxygen. In contrast, aerobic metabolism needs oxygen and yields most of the ATP, while photosynthesis is a separate process that uses light energy to build sugars. So the best description for energy production without oxygen is anaerobic metabolism.

When oxygen isn’t available, cells rely on anaerobic metabolism to make energy. Without oxygen, the electron transport chain can’t operate, so cells must regenerate NAD+ to keep glycolysis going and produce ATP through anaerobic pathways. Fermentation is a common example of these pathways, converting pyruvate into lactate or ethanol and CO2 to allow glycolysis to continue, but anaerobic metabolism is the broader term that covers all energy-producing processes that don’t require oxygen. In contrast, aerobic metabolism needs oxygen and yields most of the ATP, while photosynthesis is a separate process that uses light energy to build sugars. So the best description for energy production without oxygen is anaerobic metabolism.