Which statement best describes aerobic metabolism?

• A. Immediate energy without oxygen
• B. Breakdown of carbohydrates and fats with oxygen
• C. Breakdown of carbohydrates and fats without oxygen
• D. Breakdown of proteins with oxygen

Answer: (B)

Aerobic metabolism is the process of producing energy in the presence of oxygen by fully breaking down fuels like carbohydrates and fats to generate ATP, with carbon dioxide and water as byproducts. When oxygen is available, glucose and fatty acids are oxidized through the mitochondria via glycolysis, the Krebs cycle, and the electron transport chain, yielding a large amount of ATP. This is why the description of breaking down carbohydrates and fats with oxygen best captures aerobic metabolism. In contrast, energy production without oxygen is anaerobic and supplies much less ATP, often producing lactate in humans. Proteins are not the primary energy source under normal aerobic conditions.