The process by which glucose is produced from glycogen is called glucogenolysis. This process takes place in the liver and kidneys.

Glucose production in the reverse process of glycolysis is called gluconeogenesis. It occurs more in animal body. Less occurs in plant cells. The oil stored in the seeds of plants like rapeseed, sunflower etc. is broken down in the process of gluconeogenesis to produce sucrose or glucose. It helps in the growth of sprouts.

1. The rate of glycolysis increases when the use of ATP is faster. The rate of this process slows down when the use of ATP is reduced.
2. The amount and supply of glucose regulates this process.
3. Allosteric enzyme phosphofructokinase which catalyzes the formation of fructose 1, 6-bisphosphate from fructose 6-phosphate. Glycolysis process is dependent on its speed.

1. A variety of substances produced in the glycolysis process have metabolic functions.
2. The process of glycolysis occurs in the cytoplasm of the cell (Salisbury,1996). Hence it is called cytoplasmic respiration.
3. In this process, glucose is oxidized in the organism.
4. The key to this process is the formation of pyruvic acid. Two molecules of pyruvic acid are produced from each molecule of glucose.
5. Pyruvic acid produced in this cycle is used as raw material in Krebs cycle.
6. Glycolysis produces ATP and NADPH+H+.
7. This cycle does not require oxygen.
8. The main source of energy from food is glycolysis.
9. If pyruvic acid is not produced in this process, respiration will stop.
10. The main pathway of fructose and galactose metabolism is glycolysis.
11. ATP and NADPH+H+ generated in glycolysis account for 17% of total latent energy. Only 4% of this is expended and about 80% of the energy is stored in pyruvic acid.

Out of 9 reactions in glycolysis process, 1st, 3rd and 9th reactions are unidirectional, rest are bidirectional. The reactions are:
1. Glucose 6-phosphate is produced from glucose by the action of hexokinase enzyme. During this reaction, ADP takes part and produces ATP.
2. Fructose 6 phosphate is produced from glucose 6 phosphate under the influence of phosphoglucoisomerase enzyme. The reaction is bidirectional.
3. In the presence of the enzyme phosphofructokinase, fructose 6-phosphate is converted to fructose 1, 6-bisphosphate. At this time, ATP takes part in the reaction and produces ADP.
4. 3-phosphoglyceraldehyde and dihydroxyacetone phosphate are produced from fructose 1,6 bisphosphate by the action of aldolase enzyme. The reaction is bidirectional.
5. 1, 3 bisphosphoglyceric acid is produced from 3 phosphoglyceraldehyde under the influence of phosphoglyceral dehydrogenase enzyme. At this time, NADP participates in the reaction to form NADPH+H+. The reaction is bidirectional.
6. Phosphoglyceric acid is converted to 1, 3 bisphosphoglyceric acid, 3-phosphoglyceric acid with the help of kinase enzyme. During this reaction, ADP takes part and produces ATP. The reaction is bidirectional.
7. 2-phosphoglyceric acid is formed from 3-phosphoglyceric acid in the presence of phosphoglyceromutase enzyme. The reaction is bidirectional.
8. 2-phosphoenol pyruvic acid is produced from 2-phosphoglyceric acid by the action of inolase enzyme. The reaction is bidirectional.
9. Pyruvic acid is produced from 2-phosphoenol pyruvic acid under the action of pyruvic acid kinase enzyme. During this reaction, ADP takes part and generates ATP.

Out of 9 reactions in glycolysis process, 1st, 3rd and 9th reactions are unidirectional, rest are bidirectional. The reactions are:
1. Glucose 6-phosphate is produced from glucose by the action of hexokinase enzyme. During this reaction, ADP takes part and produces ATP.
2. Fructose 6 phosphate is produced from glucose 6 phosphate under the influence of phosphoglucoisomerase enzyme. The reaction is bidirectional.
3. In the presence of the enzyme phosphofructokinase, fructose 6-phosphate is converted to fructose 1, 6-bisphosphate. At this time, ATP takes part in the reaction and produces ADP.
4. 3-phosphoglyceraldehyde and dihydroxyacetone phosphate are produced from fructose 1,6 bisphosphate by the action of aldolase enzyme. The reaction is bidirectional.
5. 1, 3 bisphosphoglyceric acid is produced from 3 phosphoglyceraldehyde under the influence of phosphoglyceral dehydrogenase enzyme. At this time, NADP participates in the reaction to form NADPH+H+. The reaction is bidirectional.
6. Phosphoglyceric acid is converted to 1, 3 bisphosphoglyceric acid, 3-phosphoglyceric acid with the help of kinase enzyme. During this reaction, ADP takes part and produces ATP. The reaction is bidirectional.
7. 2-phosphoglyceric acid is formed from 3-phosphoglyceric acid in the presence of phosphoglyceromutase enzyme. The reaction is bidirectional.
8. 2-phosphoenol pyruvic acid is produced from 2-phosphoglyceric acid by the action of inolase enzyme. The reaction is bidirectional.
9. Pyruvic acid is produced from 2-phosphoenol pyruvic acid under the action of pyruvic acid kinase enzyme. During this reaction, ADP takes part and generates ATP.

1. Glycolysis is the first stage of respiration.
2. It occurs in the cytoplasm of the cell. Hence it is also called cytoplasmic respiration.
3. This process does not require oxygen.
4. The amount of energy produced in this process is less.
5. CO2 is not produced at this stage.
6. In this process partial oxidation of respiratory material (glucose) takes place.
7. This process is called EMP trajectory.

The word Glycolysis is formed from the Greek words Glykos meaning sugar and lysis meaning splitting. The biochemical process in which one molecule of glucose is broken down step by step into two molecules of pyruvic acid by the action of different types of enzymes is called glycolysis. In 1918, German scientists Gustave George Embden, Otto Meyerhof and Jakob Karol Parnas discovered the reactions of glycolysis. As their name suggests, glycolysis is abbreviated as the EMP pathway. Since the reactions of glycolysis take place in the cytoplasm of the cell, it is called cytoplasmic respiration.

Respiration can be divided into two stages based on the presence or absence of oxygen.
1. Aerobic Respiration: This respiration requires free oxygen and produces more energy. Respiration occurs in numerous bacteria, most fungi, algae, bryophyta, pteridophyta, plants and animals.
2. Anaerobic respiration: This respiration does not require free oxygen and produces less energy. Abiotic respiration occurs in some bacteria and single-celled fungi.

All the substances or materials that are used as raw materials in the process of respiration are called respiratory substances. Carbohydrates are the main respiratory substances. However, proteins, amino acids, fats, fatty acids, glycerol and various types of organic acids are used as respiratory substances. Glucose is the main translocated sugar in the animal body. It is used as a direct inhalation agent. Sucrose is the main translocated sugar in plants. It is broken down to produce glucose and fructose and is used in digestion.