Significance Of Glycolysis

Glycolysis is found in many living organisms and is the first step in cellular respiration. It is a glycolytic pathway, resulting in a partial breakdown of glucose to pyruvate. Glycolysis is the same pathway used for both aerobic and anaerobic respiration.

Glycolysis is an ancient metabolic pathway that has evolved long ago and is present in all organisms. It does not require oxygen and is an important pathway to produce energy in the form of ATP, both aerobically and anaerobically, which is essential for the functioning of all cells. Thus, it is an essential metabolic pathway.

All cells and tissues use this pathway to obtain energy, which is stored as ATP and NADH.

It occurs in both prokaryotes and eukaryotes.

It is used in both aerobic and anaerobic respiration.

The process of glycolysis occurs in the cytosol, making it a vital process for energy generation in organisms that lack mitochondria.

Pyruvate, the end product of glycolysis, is an intermediate of various processes including gluconeogenesis, fatty acid synthesis, and fermentation.

Even intermediates of the glycolysis process, such as DHAP (dihydroxyacetone phosphate), are utilised in other metabolic pathways; DHAP is reduced to form glycerol 3-phosphate, which is used in the formation of triglycerides.

Glycolysis interacts with a variety of other metabolic pathways, including lactate and ethanol fermentation, transamination to form alanine, the pentose phosphate pathway, glycogen metabolism, and more.

When there is a high demand of energy in muscles and there is an insufficient supply of oxygen, anaerobic glycolysis pathway is used to generate energy.

Erythrocytes derive energy from lactic acid fermentation due to the absence of mitochondria, and the lens of the eye is another example of anaerobic glycolysis.

Gluconeogenesis reversibly generates glucose back from pyruvate, as most of the reactions are reversible.

Check Out: MCQs on Prokaryotes

Overview of Glycolysis

Glycolysis is a series of enzymatic reactions that take place in the cytoplasm and is also referred to as the EMP pathway (Embden Meyerhof Parnas pathway). It is the initial step in cellular respiration, and plants and animals obtain energy from the breakdown of carbohydrates. Plants store sucrose, which gets converted to glucose and fructose; these monosaccharides then enter the glycolytic pathway in order to generate energy.

Two molecules of pyruvate are produced by the partial oxidation of glucose.

There are two phases in the process:

  • Preparatory phase, where ATP is consumed
  • Pay off phase, where ATP is produced.

There is a net yield of 2 ATPs and 2 NADH.

It is a series of ten enzymatic reactions, which converts 6C Glucose into two molecules of 3C pyruvate.

In the first phase, Glucose is phosphorylated to form fructose-1,6-bisphosphate in a three-step process, and then broken down to 3C compounds G3P (Glyceraldehyde-3-phosphate) and DHAP (Dihydroxyacetone phosphate). G3P is generated by DHAP. During this phase, two ATPs are utilized.

The second phase is an energy capturing phase, where G3P is converted into pyruvate in five steps. This process yields 4 ATPs and 2 NADH molecules.

In eukaryotic cells, pyruvate enters the mitochondria, where it is oxidatively decarboxylated to form acetyl CoA, which then enters the Krebs cycle or Citric acid cycle. In aerobic prokaryotes, this reaction occurs in the cytosol.

In anaerobic respiration, pyruvate is converted into either lactate (e.g. in muscles) or acetaldehyde, which is then further converted into ethanol and CO2 in bacteria and yeast.

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