Amphibolic Pathway
May 09, 2023, 16:45 IST
Amphibolic pathways are responsible for the breakdown as well as synthesis of compounds in the body. Cellular respiration is a prominent example of an amphibolic pathway which includes Glycolysis, Krebs cycle and Electron Transport System.
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Introduction
The term ‘amphibolic’ was coined by B.Davis in 1961. A biochemical cycle that involves both anabolic and catabolic reactions is referred to as an Amphibolic pathway. Anabolism is the synthesis of larger compounds from smaller molecules and energy whereas Catabolism is the breakdown of huge compounds to yield small molecules and energy. These reactions are the backbone of metabolism in living beings.
Respiration as an Amphibolic Pathway
Respiration is the degradation of sugars, proteins and fatty acids to produce energy in the form of ATP (Adenosine Triphosphate). However, the substrates and by-products formed in the breakdown of these compounds are utilised for synthesis of other useful molecules. Glycolysis and Krebs cycle provide many intermediate compounds and ATP for the synthesis of biomolecules. Hence respiration is amphibolic in nature.
Amphibolic Nature of Glycolysis and Krebs Cycle
Glucose is derived from carbohydrates and is converted to pyruvate by glycolysis. One glucose molecule provides about 36 ATP molecules. Pyruvate enters the Krebs cycle by a link reaction and is converted to Acetyl-CoA. When glucose is not required by the body it is converted into glycogen by glycogenesis and stored in the body.
Fats are disintegrated into glycerol and fatty acids. Glycerol is converted into glyceraldehyde-3-phosphate which is an intermediate in glycolysis and goes on to form pyruvate. Fatty acids are broken down to form Acetyl-CoA on the requirement of energy and Acetyl-CoA is used to synthesise fatty acids and phospholipids on the requirement of fats.
Proteins on the other hand are broken down into amino acids by protease enzymes. The amino acids are thus introduced into the Krebs cycle as pyruvates. Several products in the Krebs cycle are utilized for synthesis of compounds.
