The metabolic pathway of glycolysis involves the oxidative breakdown of one glucose molecule into two pyruvates by capturing some amount of ATP and NADH. Glycolysis is the common pathway that happens in both aerobic and anaerobic respiration.
Glucose is the only source of energy that is supplied to the brain, to function the brain properly the body must supply a sufficient amount of glucose to the brain via blood. Hence we can tell that glycolysis is the important process that takes place in the cell.
Glycolysis: Pathway Energetics and Significance
Glycolysis occurs in both the prokaryotes and eukaryotes. Even though there are different mechanisms that happen in the body, glycolysis is the most important one as it produces the intermediate that is required for other metabolic processes. The glycolysis process occurs in the cytosol and it is a very important process in organisms that do not contain mitochondria. The end product of glycolysis is pyruvate, which acts as an intermediate of various pathways such as gluconeogenesis, fermentation, etc.
The energetics of glycolysis include, from one glucose molecule, two molecules of glyceraldehyde 3-phosphate are formed in the second stage of glycolysis from which, the two molecules of pyruvate are obtained as end products of glycolysis. Hence the energy of glycolysis is calculated by considering two molecules of glyceraldehyde 3-phosphate.
Significance of Glycolysis:
Glucose - 6 - p is the common intermediate that is required for various metabolic reactions like glycogen synthesis, HMP pathway, etc.
Fructose - 6 - P is required for the synthesis of glucosamine.
In the HMP pathway for the synthesis of pentose, triose like glyceraldehyde - 3 - P is used.
Energetics of Anaerobic Glycolysis
Anaerobic glycolysis occurs in the absence of oxygen, during insufficiency of oxygen, and in case of the high demand of energy in the muscles, the anaerobic glycolysis pathway occurs. As the RBCs lack mitochondria, they derive energy from lactic acid fermentation. Another example where anaerobic respiration takes place is in the lens of the eye.
Two processes occur under anaerobic glycolysis, they are:
Lactic acid fermentation: This process occurs in the absence of oxygen in the muscles where lactate is converted into pyruvate with the help of an enzyme called lactate dehydrogenase.
Ethanol fermentation: In this process, glucose gets converted into ethanol instead of pyruvate.
Hence we can tell that the end product of anaerobic respiration is lactic acid or ethanol along with the ATP molecules.
Importance of Glycolysis
Glycolysis is the most important pathway,
Most of the energy used by cells comes from glucose.
It is the first pathway that is used to convert glucose into energy.
It is one of the ancient pathways that is seen as it is used by all living organisms.
It is the first main metabolic pathway of cellular respiration that produces energy in the form of ATP.
Evolutionary Significance of Glycolysis
The evolutionary significance of glycolysis includes:
Ancient prokaryotes used glycolysis before oxygen was present in the atmosphere.
Bacteria produced O2 exclusively from photosynthesis → prokaryotes generate ATP exclusively from glycolysis.
Glycolysis is the most widespread metabolic pathway and does not require any membrane-enclosed organelles.
Gluconeogenesis is a pathway that consists of a series of eleven enzyme-catalyzed reactions. The pathway will begin in either the liver or kidney, in the mitochondria or cytoplasm of those cells, it is dependent on the substrate used.
The gluconeogenesis significance is as follow:
When sufficient amounts of carbohydrates are not obtained from diet this process provides the required glucose.
By the process of glycogenolysis, the glycogen stored in the adipose tissue and skeletal muscle is converted into glucose.
It is used to clear the products of the metabolism of other tissues from the blood.
Energetics of Gluconeogenesis
Energetics of gluconeogenesis are; the six nucleotide triphosphate molecules are hydrolyzed for the synthesis of glucose from pyruvate in gluconeogenesis, whereas only two molecules of ATP are generated in glycolysis in the conversion of glucose into pyruvate.