Understanding Cellular Respiration Step by Step

Cellular respiration begins in the cytoplasm with glycolysis, the first stage of energy production from glucose.During glycolysis, one glucose molecule is broken down through ten distinct enzymatic reactions.In the first five steps, the cell actually uses two ATP molecules to modify and split the glucose.However, the later steps produce four ATP molecules, giving us a net gain of two ATP.The process also produces two NADH molecules, which will be important for later stages of cellular respiration.Finally, the glucose molecule is split into two pyruvate molecules, which will continue to the next stage of cellular respiration.Importantly, glycolysis does not require oxygen, making it an anaerobic process.Inside the mitochondrial matrix, pyruvate from glycolysis is converted into acetyl-CoA.During this conversion, CO2 is released as a waste product.Acetyl-CoA then enters the citric acid cycle, also known as the Krebs cycle.This cycle involves eight major steps, starting with the formation of citrate.Throughout the cycle, high-energy electron carriers NADH and FADH2 are produced.The cycle turns twice for each glucose molecule that entered glycolysis, as each glucose produces two pyruvate molecules.The electron carriers produced in this cycle will move on to power the electron transport chain.The electron transport chain is located in the inner mitochondrial membrane.NADH and FADH2 from earlier stages deliver high-energy electrons to the chain.As electrons move through the complexes, their energy drives proton pumps.This creates a proton gradient across the membrane, with more protons accumulating in the intermembrane space.The proton gradient powers ATP synthase, which generates ATP through chemiosmosis.When combined with earlier stages, this process generates approximately thirty-four ATP molecules per glucose molecule.