Most ATP comes from what step of cellular respiration? Electron Transport chain Kreb cycle Calvin cycle glycolysis “The Bridge”
The Correct Answer and Explanation is:
The correct answer is Electron Transport Chain.
Cellular respiration is the process by which cells convert glucose into usable energy in the form of adenosine triphosphate (ATP). It consists of three primary stages: glycolysis, the Krebs cycle, and the electron transport chain. Each stage plays a vital role in extracting energy from glucose, but they contribute differently to the total ATP yield.
Glycolysis occurs in the cytoplasm and involves breaking glucose into two molecules of pyruvate. This step produces a net gain of 2 ATP molecules and generates some high-energy electron carriers in the form of NADH. After glycolysis, pyruvate is converted into acetyl-CoA, a step sometimes referred to as the “bridge” or link reaction. This step also produces NADH but yields no direct ATP.
The Krebs cycle, also known as the citric acid cycle, takes place in the mitochondria. It processes acetyl-CoA to produce more electron carriers such as NADH and FADHâ‚‚, along with 2 ATP molecules per glucose. While important for generating electron-rich molecules, the ATP yield here remains modest.
The electron transport chain, located in the inner mitochondrial membrane, is where most ATP is produced. NADH and FADHâ‚‚ donate electrons, which are passed through a series of protein complexes. This movement pumps protons across the membrane, creating a proton gradient. As protons flow back into the mitochondrial matrix through ATP synthase, large amounts of ATP are synthesized. This process, called oxidative phosphorylation, produces approximately 34 ATP molecules per glucose.
By far, the electron transport chain is the most ATP-productive step of cellular respiration. Neither the Calvin cycle, which occurs in photosynthesis, nor the “bridge” step contributes significantly to ATP generation. Thus, the majority of energy harnessed from glucose originates in the electron transport chain.
