The process of breakdown of one molecule of glucose into two molecules of pyruvic acid through a series of biochemical reactions is called glycolysis. The whole process can be expressed by the following equation.
1. The term Glycolysis has originated from Greek work “Glycose”, (meaning sugar) and Lysis (meaning break down, dissolve, analysis), and means the breakdown of sugar. This is a complex biochemical process and is completed in ten steps.
2. Different steps of Glycolysis were worked out by G Embden, Otto Meyerhoff, and J.Parnas in 1930, hence this process is also called EMP path. This is completed in the cytoplasm of the cell and O2 is not used in the process.
3. Glycolysis takes place by the same reactions in all types of organisms and is found in both aerobic and anaerobic respiration.
4. It can be defined as, “Breakdown of a glucose molecule into pyruvic acid through a series of biochemical reactions along with the release of energy is called glycolysis”.
5. All the 10 biochemical reactions occurring during glycolysis can be studied under three heads.
1.Phosphorylation of Glucose
2.Splitting of phosphorylated hexose molecule in two molecules of phosphoglyceraldehyde
3. Formation of two molecules of pyruvic acid.
1. Phosphorylation of Glucose:
- In the first step of glycolysis one molecule of glucose changes in glucose-6-phosphate by use of one ATP molecule in the presence of hexokinase enzyme.
- In the presence of isomerase enzyme, Glucose-6-phosphate changes into fructose-6-phosphate.
- Fructose-6-phosphate using one molecule of ATP further changes into fructose 1-6-diphosphate in the presence of enzyme phosphofructokinase.
- The reactions taking place during the phosphorylation of glucose are as follows:
2. Splitting of Phosphorylated Hexose molecule in two molecules of Phosphoglyceraldehyde:
- In this reaction, fructose 1-6-diphosphate breaks down in one molecule of phosphoglyceraldehyde (3-PGAL) and one molecule of dihydroxyacetone phosphate (DHAP) in the presence of aldolase enzyme.
- These two compounds are interconvertible in the presence of triphosphate isomerase enzyme.
- Of these compounds, oxidation takes place of only 3-PGAL.
- Hence as 3-PGAL is oxidised, DHAP keeps on changing to 3- PGAL.
