We have discussed the aerobic metabolism of glucose extensively in thisclass. To capture and use the energy in glucose to make ATP, we mustutilize 4 different sequential pathways/steps. Starting with one glucosemolecule and eventually ending with CO2, H20 and ATP, list the 4pathways/steps in order and tell me what molecules enter each pathway,and what the final products of each pathway are.

All the chemical reactions that occur inside the body and sustain the life processes are together summed up as the metabolism. There are various metabolic pathways that occur inside the body like glycolysis, glycogenesis, CAC (citric acid cycle), beta-oxidation, and so on. The life processes can be anabolic (synthesizing) or catabolic (degrading).Carbohydrates are the main energy source of the human body. They include sugars, fiber, and starch. The single basic unit or monomer of any carbohydrate like glucose, galactose, fructose, and mannose is termed monosaccharide. The complete metabolism or oxidation of glucose generates carbon dioxide and water along with liberating energy as ATP (adenosine triphosphate) molecules. One molecule of glucose generates 38 ATP molecules when oxygen is abundantly present. The metabolism of 1 glucose molecule is completed in four crucial steps: Glycolysis: The metabolic pathway that takes place in the cytoplasmic region of cells and results in the cleavage of glucose into two molecules with three carbons each and the generation of energy is termed glycolysis. The overall reaction of this step is: C6H12O6 + 2 ADP + 2 [P]i + 2 NAD+ → 2 pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O Oxidative decarboxylation of pyruvate: Pyruvate is now converted to acetyl CoA (Coenzyme A) by PDC (pyruvate dehydrogenase complex) liberating CO2 and 1 molecule of NADH. The overall reaction can be summed up as: Pyruvate + NAD+ → Acetyl CoA + CO2 + NADH The TCA cycle (tricarboxylic acid cycle): It takes up the pyruvate produced from glycolysis for its further oxidation. 2 ATP molecules are generated during the TCA cycle by utilizing substrate phosphorylation. The succinyl-CoA loses CoA (Coenzyme A) to generate succinate. The energy thus produced is used to form guanosine triphosphate (GTP) from GDP and Pi (inorganic phosphate) by substrate-level phosphorylation. ATP can be produced utilizing the GTP produced in this reaction. The overall reaction can be summed up as: 2 acetyl CoA + 6 NAD+ + 2 FAD+ + 2 ADP + 2[P]i → 4 CO2 + 6 NADH + 6 H+ + 2 FADH2 + 2 ATP ETC (Electron transport chain): The two major kinds of phosphorylation that occur inside the body are substrate-level phosphorylation (Krebs cycle) and oxidative phosphorylation (electron transport chain). The electrons are carried from a one-electron donor source to a different electron acceptor. The acetyl CoA molecules derived from beta-oxidation enter the Krebs cycle and generate ATP while the NADH and FADH2 enter ETC (electron transport chain) and ATP molecules are generated from them using oxidative phosphorylation. The oxygen serves as acceptor and NADH (nicotinamide dinucleotide hydrogen) and FADH2 (flavin dinucleotide dihydrogen) as electron donors. The various complexes are only proton pumps while cytochrome c is a typical electron carrier. The overall chain of electrons can be summed up as: NADH → Complex I → Q → Complex III → cytochrome c → Complex IV → O2 The different reactions taking place at various complexes of ETC are: Complex I: (NADH + H+) + CoQ (ubiquinone) + 4 H+(matrix) → NAD+ + CoQH2 (ubiquinol) + 4 H+ (intermembrane) Complex II: Succinate + FAD → Fumarate + 2 H+(matrix) + FADH2 FADH2 + CoQ →FAD + CoQH2 Complex III: 2 CoQH2 (from site 1) + CoQ (from site 2 of complex) + 2 Cyt c (oxidized) + 2 H+ ( in matrix) → 2 CoQ + CoQH2 (site 2) + 2 Cyt c (reduced) + 4 H+ (present in intermembrane) Complex IV: 2 cytochrome c (reduced) + ½O2 + 4 H+(matrix) → 2 cytochrome c (oxidized) + 1 H2O + 2 H+ (present in intermembrane space) Complex 5 is an ATP synthase and it utiliz3es the proton gradient generated by ETC. For every 4 hydrogen ions that come into the matrix one molecule of ATP is generated. Reaction: ADP + [P] i + 4 H+ ⇌ ATP + H2O + 4 H.