What are the primary byproducts of cellular respiration in humans?

• A. Oxygen and glucose
• B. Carbon dioxide and water
• C. Nitrogen and oxygen
• D. Methane and carbon dioxide

Answer: (B)

In human cells, cellular respiration uses glucose and oxygen to produce energy (ATP). The waste products that come out of this process are carbon dioxide and water. Carbon dioxide is released as the carbon atoms from glucose are oxidized and exit the body when we breathe out. Water forms when oxygen acts as the final electron acceptor and combines with hydrogen during the electron transport chain. Put simply, glucose plus oxygen yields carbon dioxide, water, and energy. Oxygen and glucose are the reactants you start with, not the byproducts, so they aren’t the wastes produced. Nitrogen and methane aren’t produced by human cellular respiration, either, which is why those options aren’t correct.