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Cellular Respiration


Home | Glycolysis | Krebs Cycle | Electron Transport Chain | Transition Reaction

Gylcolysis can be broken down into 2 steps Glycolysis I which is endothermic activation that uses ATP) and the second is glycolysis II which is an Exothermic reaction that creates ATP and pyruvate.
Gylcolysis I
Gylcolysis I is a series of endothermic reactions. In order to start Gylcolysis I, an activation energy is required. This is source is in the form of ATP. This comes from the first reaction of Glycolysis 1 called substrate level phosphorylation. During this reaction an enzyme transfers a Pi from one substrate to another. This process can either remove a phosphate from ATP or add one to ADP. An ATP molecule is sued to add a phosphate to glucose to form glucose 6 phosphate. Another molecule of ATP is used to phosphorylize fructose 6 phosphate to fructose 1,6 diphosphate. This molecule is then reorganized to form two molecules of PGAL (Phosphoglyceraldehyde). These PGAL function as the primary reactants for Glycolysis 2.

Gylcolysis II
Glycolysis II consists of a series of exothermic reactions and helps suply the needed energy to the cell.  After glycolysis I is over all the PGAL's have t oxidized. The electropms go up to NAD+ and then they are reduced. H+ is joins NAD to make NADH. After PGAL is oxidized it is able to take another free phospahte ion from the cytoplasme and forms 1,3 diphosphoglycerate. Two PGAP molecules are made for each glucose molecule that enters glycolysis. With the help of enzymes, 2 ADP molecules remove a phospahte from PGAP and they form 3-phophoglycerate (PGA). 2 molecules of atp are produced for each molecule of PGAP. Substrate level posphorylation produced the ATP.   Another substrate level phosphorylation reaction takes place. Once again, with the help of enzymes ADP removes the final phosphate from PEP giving off a molecule of ATP per PEP, producing pyruvate (pyruvic acid) which is the final product as well as the goal of cellular respiration.

Glycolysis I,II


Glycolysis Facts


- Glycolysis does not need oxygen for any of its chemical    reactions.

- Glycolysis happens in the cytoplasm  of cells.

- Glycolysis is the one metabolic pathway found in all living organisms.