Give an account of glycolysis, Where does it occur ? What are the end products? Trace the fate of these products in both aerobic, and anaerobic respiration.

Explanation

Glycolysis occurs in the cytoplasm. The end product of glycolysis is pyruvic acid.
Glycolysis is the process in which glucose undergoes partial oxidation to form two molecules of pyruvic acid. It is as follows.
1) in the first of glycolysis, a phosphate group is added to glucose molecule in the formation of glucose-6-phosphate. ATP is, utilised. This reaction is catalysed by hexokinase enzyme.
Glucose + ATP `overset( "hexokinase")rarr` Glucose-6-phosphate + ADP
2) Phosphohexokinase enzyme catalyses the conversion of glucose-6-phosphate to its-isomer fructose-6-phosphate.
Glucose-6-phosphate `overset("phosphohexose isomerase")rarr` Fructose 6-phosphate
3) Fructose-6-phosphate undergoes phosphorylation resulting Fructose-1,6 bisphosphate. In this step ATP is utilised. This reaction is done by enzyme phosphofructokinase.
Fructose-6-phosphate + ATP `overset("Phosphofructokinase")rarr` ructose1-6 bisphosphate + ADP
4) Fructose. 1-6 bisphosphate with the help of enzyme aldolase splits into 2 molecules. They are glyceraldehyde 3 phosphate and dihydroxyacetone phosphate (DHA Fructose-1,6 bisphosphate `overset("Aldolase")rarr` Glyceraldehyde-3 phosphate + Dihydroxyacetone phosphate
5) Among the two trioses, only Glyceraldehyde 3 phosphate directly participates in the subsequent reaction.s.
On the other hand, dihydroxyacetone phosphate gets converted into glyceraldehyde-3-phosphate in the presence of triose phosphate isomerase and can participate in the next reaction of glycolysis.
Dihydroxyacetone phosphate, `overset("Triose phosphate isomerase")rarr` Glyceraldehyde-3-phosphate.
6) Glyceraldehyde-3-phosphate undergoes oxidation as well as phosphorylation in the presence of glyceraldehyde 3 phosphate dehychoganase resulting in the formation of 1-3 bisphospho glyceric acid and NADH.
Glyceraldehyde-3-phosphate + `NAD^(+)`
`overset("Glyceraldehyde-3-phosphate dehydrogenase ")rarr` 1,3 bisphosphoglyceric acid + NADH + `H^(+)`
7) Phosphoglycerokinase enzyme catalyses the dephosphorylation of 1,3 bisphosphoglyceric acid resulting in the formation of 3 phosphoglyceric acid. ADP molecule.accepts the phosphate released in this reaction and gets converted into high energy. compound ATP. This process of formation is known as substrate level phosphorylation.
1,3 bisphosphoglyceric acid + ADP+iP `overset("Phosphoglycerokinase ")rarr` 3 Phosphoglyceric acid + ATP
8) Phosphoglyceromutase enzyme catalyses the transfer of phosphate group from 3-carbon.position of 3 PGA to 2-carbon: position leading to the formation of 2PGA.
3 PGA `overset("Phosphoglyceromutase")rarr` 2 PGA
9) The enzyme enolase catalyses the removal of one water molecule from 2-phospho- glyceric acid resulting in the formation of phosphoenol pyruvic acid.
2 phosphoglyceric acid `overset("Enolase")rarr` Phosphoenol pyruvic acid `+H_2O`
10) Phosphoenol pyruvic acid undergoes dephosphorylation in the presence of the enzyme pyruvic, kinase and results in the formation of pyruvic acid. ADP is converted to ATP. This is substrate level of phosphorylation.
Phosphoerol pyruvic acid (PEP) + ADP `overset("Pyruvic kinase")rarr` Pyruvic acid + ATP
Fate of Pyruvic acid : The ultimate fate of pyruvic acid which is an end product of glycolysis depends upon the availability of oxygen. In the presence of oxygen it is completely oxidized into `CO_2` and `H_2O` If oxygen is not available, the pyruvic acid is converted to ethyl alcohol or other organic substances by fermentation during anaerohir roeninntion .