Carbohydrate Metabolism
Glucose is phosphorylated twice and cleaved to form two molecules of
glyceraldehyde-3-phosphate (G-3-P). The two ATP molecules consumed during
this stage are like an investment, because this stage creates the actual
substrates for oxidation in a form that is trapped inside the cell.
Glyceraldehyde-3-phosphate is converted to pyruvate. Four ATP and two NADH
molecules are produced. Because two ATP were consumed in stage 1, the net
production of ATP per glucose molecule is 2.
The glycolytic pathway can be summed up in the following equation:
D-Glucose + 2 ADP + 2 Pi 2 NAD+ 2 pyruvate + 2 ATP + 2 NADH + 2H+ + 2H2O
The 10 reactions of the glycolytic pathway
1. Synthesis of glucose-6-phosphate
2. Conversion of glucose-6-phosphate to fructose-6-phosphate
3. The phosphorylation of fructose-6-phosphate. Phosphofructokinase-1 (PFK-1)
4. Cleavage of fructose-1,6-bisphosphate
5. The interconversion of glyceraldehyde-3-phosphate and dihydroxyacetone
phosphate
6. Oxidation of glyceraldehyde-3-phosphate.
7. Phosphoryl group transfer
8. The interconversion of 3-phosphoglycerate and 2-phosphoglycerate
9. Dehydration of 2-phosphoglycerate
10. Synthesis of pyruvate
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