Oxygen combining with sugar to form carbon dioxide and water is called what?

• A. Fermentation
• B. Respiration
• C. Photosynthesis
• D. Metabolism

Answer: (B)

Cellular respiration is the process by which cells use oxygen to release energy from sugar, producing carbon dioxide and water as waste. In this process, glucose reacts with oxygen in mitochondria through glycolysis (in the cytoplasm), the citric acid cycle, and the electron transport chain. The final electron acceptor is oxygen, which helps form water, while the breaking of chemical bonds in glucose releases energy captured as ATP. The overall result is glucose plus oxygen turning into carbon dioxide, water, and ATP. This is different from fermentation, which happens without oxygen and yields less energy, and from photosynthesis, which uses light to build sugar from carbon dioxide and water. Metabolism is the broad term for all the chemical reactions that sustain life.