The products of cellular respiration include

• A. Water
• B. Carbon dioxide gas
• C. Energy (ATP)
• D. All of the above

Answer: (D)

Cellular respiration releases energy from glucose and produces waste molecules, so you end up with energy in the form of ATP along with carbon dioxide and water as byproducts. The water comes from the final step of the electron transport chain, where oxygen acts as the final electron acceptor and combines with electrons and hydrogen ions to form H2O. Carbon dioxide is released when carbon atoms are removed from glucose during pyruvate oxidation and the Krebs cycle. ATP is produced throughout the process, including substrate-level phosphorylation in glycolysis and the Krebs cycle, with the majority generated during oxidative phosphorylation in the electron transport chain. Because all three—water, carbon dioxide, and ATP—are produced, the correct choice is all of the above.