Which process releases energy by breaking down glucose in the presence of oxygen?

• A. Photosynthesis
• B. Fermentation
• C. Cellular Respiration
• D. Osmosis

Answer: (C)

Cellular respiration releases energy by breaking down glucose in the presence of oxygen. In this aerobic process, glucose is first split in the cytoplasm during glycolysis, forming pyruvate. The pyruvate then enters the mitochondria and is further processed through the citric acid cycle and the electron transport chain, where most ATP is produced through oxidative phosphorylation. The end products are ATP, carbon dioxide, and water, with a typical yield of about 30–32 ATP per glucose in many cells. This contrasts with photosynthesis, which uses light energy to synthesize glucose; fermentation, which also breaks down glucose but without oxygen and yields much less ATP along with byproducts; and osmosis, which is simply the diffusion of water across a membrane and does not involve breaking down glucose or producing energy.