Question

What is the main purpose of Glycolysis?

Answer 1

Glycolysis is an ancient metabolic pathway that has evolved over time and is found in almost all living organisms. In living organisms, glycolysis is the first step in the cellular respiration process. It takes place in both prokaryotes and eukaryotes.

Complete answer:
Glycolysis is a series of reactions that break glucose into two three-carbon molecules called pyruvates and extract energy from it. Glycolysis, on the other hand, does not require oxygen, and it is found in many anaerobic species that do not use oxygen.

The first step of glycolysis consumes energy, while the second phase completes the conversion to pyruvate and produces ATP and NADH for cell use. Glycolysis yields a net gain of two pyruvate molecules, two ATP molecules, and two NADH molecules for use as energy by the cell. After the conversion of glucose to pyruvate, the glycolytic pathway connects to the Krebs Cycle, which provides extra ATP for the cell's energy needs. Some important characteristics of glycolysis are-

- Both prokaryotes and eukaryotes have it.
- It is used in aerobic as well as anaerobic respiration.
- Since glycolysis takes place in the cytosol, it is a critical source of energy for organisms that lack mitochondria.
- And glycolysis intermediates are used in other metabolic pathways; for example, DHAP (dihydroxyacetone phosphate) is reduced to glycerol 3-phosphate, which is used in triglyceride production.
- Lactate and ethanol fermentation, transamination to form alanine, the pentose phosphate pathway, glycogen metabolism, and other processes are all interconnected by glycolysis.
- When muscles have a high demand for energy and there is a lack of oxygen, the anaerobic glycolysis pathway is used to produce energy.
- Since erythrocytes lack mitochondria, they rely on lactic acid fermentation for energy. Another example of anaerobic glycolysis is the lens of the eye.
- The purpose of glycolysis is to produce energy from sugar in the form of ATP and NADH. It also produces pyruvate which is the intermediate for several other nutrient metabolisms.

The main purpose of glycolysis is to provide pyruvate for the trichloroacetic acid (TCA) cycle, not to make adenosine 5′-triphosphate. The glycolytic production of pyruvate reduces the cytosol by increasing the ratio of NADH [a reduced form of $NAD^+$ (nicotinamide adenine dinucleotide)] to $NAD^+$.

Note: The net gain of the energy-rich molecules ATP and NADH during the second half of glycolysis is known as the 'pay-off phase.' Because glucose produces two triose sugars in the preparatory phase, each reaction in the pay-off phase occurs twice for each glucose molecule. This results in 2 NADH molecules and 4 ATP molecules, for a net gain of 2 NADH molecules and 2 ATP molecules from the glycolytic pathway per glucose molecule.