Glycolysis is the sequence of reactions that converts glucose into pyruvate with the concomitant production of a relatively small amount of ATP.

Glycolysis can be carried out anerobically (in the absence of oxygen) and is thus an especially important pathway for organisms that can ferment sugars. For example, glycolysis is the pathway utilized by yeast to produce the alcohol found in beer. Glycolysis also serves as a source of raw materials for the synthesis of other compounds. For example, 3 phosphoglycerate can be converted into serine, while pyruvate can be aerobically degraded by the Krebs or TCA cycle to produce much larger amounts of ATP.

There are 5 important types of reactions that occur in glycolysis:

  1. phosphoryl transfer: a phosphoryl group is transferred from ATP to a glycolytic intermediate, or from the intermediate to ADP, by a kinase. This reaction is characterized by the transfer of the phosphoryl group from ATP to an alcohol. The alcohol gives up the hydrogen while ADP and an organic phosphate are yielded.

  2. phosphoryl shift: a phosphoryl group is shifted from one oxygen atom to another within a molecule by a mutase. This reaction is characterized by the movement of a phosphoryl group from oxygen to an alcohol oxygen in the same molecule. The alcohol hydrogen is removed and binds to the formerly phosphorous-bound oxygen. The original compound's chemical nature can be extensively altered by this shift.

  3. isomerization: the conversion of a ketose to an aldose, or vice versa, by an isomerase. In the ketose-aldose conversion, the alcohol hydrogen is transferred to the carbonyl group, thus transforming the original alcohol group to a carbonyl and the original carbonyl to an alcohol. The exact reverse is true for an aldose-ketose isomerization.

  4. dehydration: the removal of water by a dehydratase. This reaction is characterized by the removal of a water molecule from an alcohol. This yields a carbon-carbon double bond in the original molecule.

  5. aldol cleavage: the splitting of a carbon-carbon bond in a reversal of an aldol condensation by an aldolase. This reaction is characterized by the splitting of a carbon-carbon bond. This yields an aldehyde and a ketose.

From the BioTech Project at For further information see the BioTech homenode.