Release of energy from
glucose
Glycolysis is the sequence of reactions that converts
glucose into pyruvate with the concomitant production of
a relatively small amount of ATP. Glucose is the
starting material and two molecules of pyruvate are the
end products of the pathway. Subcellular site of the
pathway is the cytosol. Glycolysis is a linear pathway
of ten enzyme mediated steps.
Phases of glycolysis
Pathway has two phases: Energy investment phase and energy
generation phase. Energy investment phase is also called preparatory
phase and consists of first five steps. Here the end product is
glyceraldehyde - 3 � phosphate. Energy generation phase is also
known as payoff phase and consists of last five steps and end
products are two pyruvate molecules.
Energy yield from the pathway
It can occur in presence or absence of oxygen. Altogether there are
ten steps involved and in aerobic glycolysis net ATP gain is 8 and
the pyruvate enters the citric acid cycle, oxidized to CO2
and H2O.
Anaerobic glycolysis
Under anaerobic conditions, net ATP gain is 2 from substrate level
phosphorylation. NADH gets accumulated which is reoxidized via
lactic acid and alcohol fermentation.
Sources of glucose for glycolysis
Glycogen, dietary disaccharides and monosaccharides also enter the
glycolytic pathway, since they are the sources of glucose.
