When cells use oxygen and nutrients to produce energy, water, and carbon dioxide, the process is called?

• A. Cellular respiration
• B. Photosynthesis
• C. Digestion
• D. Metabolism

Answer: (A)

Cellular respiration is the process by which cells generate energy by using oxygen to break down nutrients, mainly glucose, into ATP, with water and carbon dioxide as end products. The energy-producing steps occur in the mitochondria, starting with glycolysis in the cytoplasm, then the citric acid cycle, and finally the electron transport chain where most ATP is made. This aerobic pathway is how cells efficiently extract energy from fuels when oxygen is available. Photosynthesis, on the other hand, uses light to make glucose from carbon dioxide and water and releases oxygen, so it’s energy production from a different direction. Digestion is the mechanical and chemical breakdown of food for absorption, not the cellular process of energy production. Metabolism is the broader set of all chemical reactions in the body, within which cellular respiration is a specific energy-generating pathway.