dr.ehab carbohydrate metabolism

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