Ace Your Honors Biology Final 2026 – Unlock the Secrets of Life and Science Success!

Energy release from glucose in the presence of oxygen comes from cellular respiration, an aerobic pathway that fully oxidizes glucose to carbon dioxide and water and stores the energy as ATP. The process begins with glycolysis in the cytoplasm, which converts glucose into pyruvate and makes a small amount of ATP and NADH. When oxygen is available, pyruvate enters the mitochondria, is converted to acetyl-CoA, and feeds into the citric acid cycle. The NADH and FADH2 produced then drive the electron transport chain, where their electrons flow through protein complexes to pump protons and power ATP synthase, generating a large yield of ATP. The overall reaction uses oxygen and releases CO2 and water as end products.

This distinguishes it from fermentation, which occurs without oxygen and yields much less ATP, and from glycolysis alone, which can occur without oxygen but provides only a small amount of energy before the remaining steps of respiration.