Which gas is the primary waste product of aerobic metabolism and is expelled by the lungs?

Which gas is the primary waste product of aerobic metabolism and is expelled by the lungs?

• A. Oxygen
• B. Hydrogen
• C. Carbon Dioxide
• D. Nitrogen

Answer: (C)

During aerobic metabolism, cells use oxygen to oxidize nutrients to release energy. This process produces carbon dioxide as a byproduct, especially during the citric acid cycle and related decarboxylation steps. Oxygen is consumed to drive these reactions, while carbon dioxide is the waste gas that must be removed. The CO2 travels in the blood to the lungs and is exhaled. Hydrogen is incorporated into water during metabolism, and nitrogen mainly remains bound in amino groups rather than being expelled as a gas. So carbon dioxide is the gas expelled by the lungs.

During aerobic metabolism, cells use oxygen to oxidize nutrients to release energy. This process produces carbon dioxide as a byproduct, especially during the citric acid cycle and related decarboxylation steps. Oxygen is consumed to drive these reactions, while carbon dioxide is the waste gas that must be removed. The CO2 travels in the blood to the lungs and is exhaled. Hydrogen is incorporated into water during metabolism, and nitrogen mainly remains bound in amino groups rather than being expelled as a gas. So carbon dioxide is the gas expelled by the lungs.