Glycolysis

Glycolysis is a pathway which converts glucose into energy

Role of glycolysis

Glycolysis is an energy-releasing process which takes place in the cytoplasm of all cells, during which glucose is degraded to provide energy. The initial stages require input of two molecules of ATP although the subsequent stages produce four.

Stages of glycolysis

Glucose undergoes many changes due to specific enzymes. It is in turn through the many stages converted into:

• D-Glucose-6-phosphate ;
• β-D-Fructose-6-phosphate ;
• β-D-Fructose-1,6-diphosphate ;
• Dihydroxyacetone phosphate ;
• D-glyceraldehyde-3-phosphate ;
• D-glyceraldehyde-3-phosphate ;
• 1,3-diphospho-D-glycerate ;
• 3-phospho-D-glycerate ;
• 2-phospho-D-glycerate ;
• Phosphoenolpyruvate ;
• Pyruvate ;
• Acetyl-CoA .

Yield of glycolysis

The many stages of glycolysis produce a positive energy yield leading in total to the production of two molecules of ATP per molecule of glucose used. Overall:

• 1 mole of glucose ;
• 2 moles of oxidised coenzymes ;
• 2 moles of ADP ;
• and 2 moles of Pi (inorganic phosphate) are used.

And:

• 2 moles of pyruvate ;
• 2 moles of reduced coenzymes ;
• 2 moles of ATP ;
• and 2 moles of water are produced.

Continuation of glycolysis

The pyruvate obtained can then be transferred into the mitochondrium where it follows the Krebs cycle. Depending on whether oxygen is present or absent in the medium gives respectively acetyl-CoA and carbon dioxide or lactate.