Which process releases energy by breaking down glucose in the presence of oxygen?

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

Answer: (A)

The main idea here is that energy is released from glucose when it is fully broken down in the presence of oxygen. In cells, aerobic respiration uses oxygen to completely oxidize glucose through a sequence of steps in the mitochondria—glycolysis, the citric acid cycle, and the electron transport chain. Oxygen acts as the final electron acceptor in the chain, allowing a large amount of energy to be captured as ATP. This contrast with other processes: without oxygen, cells rely on anaerobic pathways that produce far less energy and different end products, like lactic acid or ethanol. Photosynthesis, on the other hand, builds glucose using light energy, not releases its energy. So the process that releases energy by breaking down glucose with oxygen is aerobic respiration.