glycolysis is the first of a set of series of reactions that oxidizes glucose in cellular respiration. it occurs in the cytoplasm of the cell.
start with glucose.
1. phase 1 of glycolysis begins. one molecule ATP is used, dephosphorylated to ADP and Pi. glucose changes into glucose-6-phosphate.
2. glucose-6-phosphate becomes fructose-6-phosphate (5-carbon sugar instead of 6-carbon sugar)
3. one molecule ATP is used, dephosphorylated to ADP and Pi. allosteric inhibition via ATP binding to enzyme phosphofructokinase when ATP levels are too high (feedback inhibition). phosphofructokinase catalyzes change of fructose-6-phosphate to fructose-1,6-biphoshphate.
4 and 5. fructose-1,6-biphosphate splits into two molecules: dihydroxyacetone phosphate and glyceraldehyde-3-phosphate.
6. phase 2 of glycolysis begins. two molecules NAD+ are reduced to become NADH. two glyceraldehyde-3-phosphates become two 1,3-biphosphoglycerates.
7. two molecules ADP are phosphorylated to two molecules ATP. this is energy payoff of two ATP molecules used in phase 1. the two 1,3-biphosphoglycerates become two 3-phosphoglycerates.
8. two 3-phosphoglycerates become two 2-phosphoglycerates.
9. two 2-phosphoglycerates become two molecules phosphoenolpyruvate.
10. two molecules ADP are phosphorylated to two molecules ADP. two molecules phosphoenolpyruvate are dephosphorylated to two molecules pyruvate.
end product of glycolysis: 2 NADH, 2 ATP, 2 pyruvate.
pyruvate moves from cytoplasm into mitochondrial matrix.
it loses a carbon via carbon dioxide, is oxidized when an NAD+ is reduced to NADH, and reacts with coenzyme A to form acetyl CoA.
citric acid cycle takes place in mitochondrial matrix and is the final set of reactions of glucose oxidation. cycle revolves twice for each molecule of glucose.
start with acetyl CoA.
1. input of water. allosteric regulation via ATP which inhibits acetyl CoA becoming citrate when ATP levels are too high.
2. citrate becomes isocitrate.
3. NAD+ reduced to NADH. loss of a carbon via carbon dioxide. isocitrate becomes alpha-ketoglutarate. allosteric inhibition via ATP when ATP levels are too high; competitive inhibition via NADH when NADH levels are too high.
4. NAD+ reduced to NADH. loss of a carbon via carbon dioxide. alpha-ketoglutarate becomes succinyl-CoA. allosteric inhibition via ATP when ATP levels are too high; competitive inhibition via NADH when NADH levels are too high.
5. ADP is phosphorylated to become ATP (or GTP to GDP). succinyl-CoA becomes succinate.
6. FAD+ is reduced to FADH2. succinate becomes fumarate.
7. input of water. fumarate becomes malate.
8. NAD+ is reduced to NADH. malate becomes oxaloacetate and one rotation of the citric acid cycle is finished.