Page 3 - Lesson notes- Plant Respiration

Glycolysis

The scheme of glycolysis is given by Gustav Embden, Otto Meyerhof, and J. Parnas. It
is also called as EMP pathway.

Glycolysis is the partial oxidation of glucose or similar hexose sugar into two

molecules of pyruvic acid through a series of enzyme mediated reaction releasing
some ATP and NADH2. It occurs in cytoplasm.

In plants glucose is derived from sucrose or from storage carbohydrates. Sucrose is

converted into glucose and fructose by enzyme invertase.
Glycolysis starts with phosphorylation of glucose in presence of enzyme hexokinase to

form Glucose-6-phosphate. One molecules of ATP is used in this process.

In next steps Glucose-6-phosphate is converted into fructose-6-phosphate, catalysed by
enzyme phosphohexose isomerase.

Fructose-6-phosphate uses another molecule of ATP to form Fructose-1-6 biphospahte
in presence of enzyme phosphfructokinase.

In glycolysis two molecules of ATP are consumed during double phosphorylation of
glucose to fructose 1,6 biphosphate. Two molecules of NADPH2 are formed at the time

of oxidation of glyceraldehyde 3-phosphate to 1,3 biphosphoglycerate. Each NADH is
equivalent to 3ATP, so that net gain in glycolysis is 8 ATP.

Pyruvic acid is the key product of glycolysis, further breakdown of pyruvic acid

depends upon the need of the cell.
In animal cells, like muscles during exercise, when oxygen is insufficient for aerobic

respiration, pyruvic acid is reduced to Lactic acid by enzyme lactate dehydrogenase
due to reduction by NADH2.