Ten Steps of Glycolysis

Lesson 17 : Glycolysis

Ten Steps of Glycolysis

  1. glucose --> glucose 6-phosphate by hexokinase G = -8.0 kcal/mole
  2. Hexokinase also works on mannose and fructose at increased.

    Serves to trap glucose in the cell --> a phosphorylated molecule cannot leave

  3. Glucose 6-phosphate --> fructose 6-phosphate by glucose 6-phosphate isomerase
  4. Example of aldose--> ketose isomerization.

    Enzyme is very stereospecific.

    Reaction is near equilibrium in cell --> not a control point in glycolysis

  5. Fructose 6-phosphate --> fructose 1,6-bisphosphate by phosphofructokinase-1 (PFK-1)
  6. Reaction has G = -5.3 kcal/mole and is metabolically irreversible.

    Represents the first committed step in glycolysis.

  7. Fructose 1,6-bisphosphate --> dihydroxyacetone phosphate + glyceraldehyde 3-phosphate by fructose 1,6 bisphosphate aldolase.
  8. DHAP --> glyceraldehyde 3-phosphate by triose phosphate isomerase
  9. Also catalyzes aldose--> ketose conversion.

    Rate is diffusion controlled (substrate is converted to product as fast as substrate is encountered).

  10. glyceraldehyde 3-phosphate --> 1,3-bisphosphoglycerate by glyceraldehyde 3-phosphate dehydrogenase
  11. One molecule of NAD+ is reduced to NADH --> respiratory chain

  12. 1,3 bisphosphoglycerate --> 3-phosphoglycerate
  13. Phosphoryl group transfer to ADP to form ATP.

    Because phosphate group comes from a substrate molecule, called substrate level phosphorylation

    First ATP-generating step of glycolysis.

  14. 3-phosphoglycerate --> 2-phosphoglycerate by phosphoglycerate mutase
  15. Mutases are enzymes that transfer phosphoryl groups from one part of a substrate molecule to another.

  16. 2-phosphoglycerate --> phosphoenolpyruvate (PEP) by enolase (forms double bond)

  17. PEP --> pyruvate
  18. Second time for substrate level phosphorylation.

    Reaction is metabolically irreversible.(Figure)

Last modified: Monday, 30 January 2012, 5:40 AM