Splitting of Sugar, Oxidation/ Reduction & ATP Generation

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The next reaction shows us the meaning of "glycolysis" or the splitting of glucose. The fructose bisphosphate molecule is split into two molecules each containing 3 carbons as the backbone. FBP is split into two 3-carbon molecules called G3P, or glyceraldehyde 3-phosphate. Notice that the phosphate groups are still attached to the original carbon 1 and carbon 6 which were present in the glucose molecule. Electron Carrier Molecules & Phosphorylation The next reaction involves oxidation, or the loss of electrons. High energy electrons from hydrogen atoms are removed and transferred to an electron carrier molecule. NAD* (nicotinamide adenine dinucleotide) is reduced to NADH plus H. Two hydrogen atoms are removed from each G3P molecule. This is the oxidation reaction. NAID+ accepts two hydrogen electrons and 1 proton (hydrogen ion or H+) while a second H+ is left in the aqueous solution of the cytoplasm. This is the reduction reaction. As part of these oxidation-reduction reactions, an inorganic phosphate group is added to each G3P molecule. Inorganic phosphate (1-13PO4) is utilized rather than a phosphate group from ATP. Inorganic phosphate is freely available in the cytoplasm. The new molecule now contains two phosphate groups and is called 1,3-bisphosphoglycerate (BPG). 1st Substrate Level Phosphorylation, Rearrangement of 3PG, 2nd Substrate Level Phosphorylation & Molecular Scorecard Finally, we are ready to harvest some ATP molecules. One phosphate group at a time is harvested from each BPG molecule. This phosphate group is added to a precursor molecule of ATP. The phosphate from BPG is attached to ADP, and in the process ADP is converted to ATP. The resulting molecule is called 3-phosphoglycerate (3PG). 3PG is rearranged into PEP (phosphoenolpyruvate) by the removal of a water molecule and the transfer of the phosphate group to the middle carbon atom. A molecule of water is released as well during this reaction.

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