Glycolysis

Glycolysis -

1.a series of reactions in which glucose is split and finally forms two molecules of pyruvic acids.

2.Each reaction is controlled by an enzyme.

3.Takes place at the beginning of aerobic respiration.

4.It occurs in the cytoplasm of the cell

5.It requires no oxygen

  Initially, phosphorylation of glucose to form fructose diphosphate occurs.

 Glycolysis

a)Two molecules of ATP are required to form fructose diphosphate

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b)The process is important to raise the energy level of the glucose as it consists of only low energy bonds.

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c)This is to create high-energy carbon-phosphate bond so that more energy can be tapped from it later

 

Fructose diphosphate is then split to form phosphoglyceraldehyde (PGAL) and dihydroxy-acetone phosphate (DHAP).

They are triose phosphates.

The PGAL and DHAP are inter-convertible, so one glucose molecule is split into two triose molecules.

The two triose phosphates undergo dehydrogenation in which hydrogen ions are removed and accepted by coenzyme NAD to form two NADH + H+.

When the two NADH + H+ enters the mitochondria, a molecule each of ATP is required. Therefore, only two net molecules of ATP can be produced from each NADH + H+ through oxidative phosphorylation.

Substrate level phosphorylation then occurs.

Two ATP can be formed through phosphorylation at substrate level from each triose phosphate, in which the phosphate ion is transferred to ADP

 

This process occurs four times forming 4 ATP and 2 pyruvates, twice when each pyruvate is formed

•            Two ATP net are produced, as two ATP are used up initially 

•    If the two NADH + H+ enter the mitochondria to form ATP by oxidative phosphorylation, then 6 ATP can be formed.