Glycolysis the breakdown of a glucose molecule into two pyruvate molecules. It is an example of substrate level phosphorylation. It occurs in the cytoplasm, whether in aerobic or anaerobic conditions.
Glucose > Glucose-6-phosphate > Fructose-6-phosphate > Fructose 1,6 biphosphate > 2 x phosphoglyceraldehyde > 2 x 1,3-biphosphoglycerate > 2 x 3-phosphoglycerate > 2 x phosphoenolpyruvate > 2 x pyruvate
NB
Glucose > Glucose-6-phosphate: 1 x ATP is used
Fructose-6-phosphate > Fructose 1,6 biphosphate: 1 x ATP is used
These two steps are known as the energy investment phase.
1,3-biphosphoglycerate > 3-phosphoglycerate: payoff of 1 x ATP per molecule (total 2 ATP)
2 x phosphoenolpyruvate > 2 x pyruvate: payoff of 1 x ATP (total 2 ATP)
These two steps constitute part of the energy payoff phase.
Net gain: 2 ATP per molecule of glucose
Also note that NAD is reduced to form NADH when phosphoglyceraldehyde reacts to form 1,3-biphosphoglycerate.
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