Answer:
Explanation:
1.During glycolysis,four molecules of ATP are formed,and two are expended to cause the initial phosphorylation of glucose to get the process going.This gives a net gain of two molecules of ATP
For every glucose molecule that undergoes cellular respiration, the citric acid cycle is carried out twice; this is because glycolysis (the first stage of aerobic respiration) produces two pyruvate molecules per glucose molecule. During pyruvate oxidation (the second stage of aerobic respiration), each pyruvate molecule is converted into one molecule of acetyl-CoA—the input into the citric acid cycle. Therefore, for every glucose molecule, two acetyl-CoA molecules are produced. Each of the two acetyl-CoA molecules goes once through the citric acid cycle.
The citric acid cycle begins with the fusion of acetyl-CoA and oxaloacetate to form citric acid. For each acetyl-CoA molecule, the products of the citric acid cycle are two carbon dioxide molecules, three NADH molecules, one FADH2 molecule, and one GTP/ATP molecule. Therefore, for every glucose molecule (which generates two acetyl-CoA molecules), the citric acid cycle yields four carbon dioxide molecules, six NADH molecules, two FADH2 molecules, and two GTP/ATP molecules. The citric acid cycle also regenerates oxaloacetate, the molecule that starts the cycle.
While the ATP yield of the citric acid cycle is modest, the generation of coenzymes NADH and FADH2 is critical for ATP production in the final stage of cellular respiration, oxidative phosphorylation. These coenzymes act as electron carriers and donate their electrons to the electron transport chain, ultimately driving the production of most of the ATP produced by cellular respiration.
