What stage of aerobic cellular respiration produces the most ATP? Group of answer choices glycolysis transition reaction Kreb’s Cycle electron transport chain
The Correct Answer and Explanation is:
Correct Answer: Electron Transport Chain
The electron transport chain (ETC) is the stage of aerobic cellular respiration that produces the most ATP (adenosine triphosphate). This process occurs in the inner membrane of the mitochondria and is the final stage of aerobic respiration.
During aerobic respiration, glucose is broken down in a multi-step process to release energy stored in its chemical bonds. The first step is glycolysis, which takes place in the cytoplasm and produces a net gain of only 2 ATP molecules per glucose molecule. The transition reaction follows, converting pyruvate into acetyl-CoA, but this step does not produce any ATP. Then, the Krebs cycle (also known as the citric acid cycle) occurs in the mitochondrial matrix and generates 2 more ATP molecules per glucose.
The real energy payoff happens in the electron transport chain. Here, the NADH and FADH₂ molecules, which were produced during glycolysis, the transition reaction, and the Krebs cycle, donate their high-energy electrons to the chain. These electrons move through a series of protein complexes in the inner mitochondrial membrane. As the electrons pass along the chain, energy is used to pump protons (H⁺) across the membrane, creating a proton gradient.
This gradient powers an enzyme called ATP synthase, which adds a phosphate group to ADP to form ATP. This process is known as chemiosmosis. From one glucose molecule, the ETC can produce approximately 32 to 34 ATP molecules, making it by far the most efficient and productive stage of cellular respiration.
In total, aerobic respiration yields about 36 to 38 ATP molecules, with the majority coming from the ETC. This makes the electron transport chain the primary source of ATP during the breakdown of glucose in the presence of oxygen
