Glycolysis

1. Glycolysis is a catabolic pathway through which glucose (C6H12O6) is oxidized to pyruvate (CH3COCOO−). It takes place in the cytosol of both eukaryotic and prokaryotic cells. During the first steps of glycolysis, 2ATP molecules are used to attach two phosphates to the glucose molecule, leaving a 6-carbon sugar diphosphate and 2 ADP molecules. Afterwards, the 6-carbon sugar diphosphate is split into two 3-carbon sugars by the enzyme Isomerase. The two 3-carbon sugar molecules then both undergo another process to be turned into pyruvate. Each 3-carbon sugar phosphate finally, after transferred electrons and H+ to NAD+ to form NADH+ and various other enzymatic reactions, releases 2 ATP molecules and pyruvate by substrate-level phosphoralation with the help of the enzyme Pyruvate kinase. The Krebs cycle occurs in the matrix of the mitochondria and with the presence of oxygen, is a process by which various enzymes complete the oxidation of the organic fuel. The Pyruvate dehydrogenase complex catalyzes three reactions, getting rid of Pyruvate’s carboxyl group (COO−) because it was already fully oxidized, using the remaining 2-carbon fragment to form acetate while also transferring extracted electrons to NAD+ to form NADH+, and lastly attaching coenzyme A to acetate, forming acetyl CoA. Since this whole process was done for 2 Pyruvate molecules, we have two acetyl CoA molecules. The acetyl CoA then enters the Krebs cycle and is attached to a 4-carbon molecule. The 2 new 6-carbon molecules, Citrate, then follow the remaining steps of the Krebs cycle, producing a total of six NADH+ molecules, two FADH2 molecules, 4 CO2 molecules, and transferring a phosphate group from GDP to GTP to synthesize 2 ATP molecules. In eukaryotes, the electron transport chain takes place in the inner membrane of the mitochondria. The most electron transport chains contain multi-protein complexes with tightly bound prosthetic groups. The electrons form the NADH+ and the FADH+ molecules