Amphibolic Pathway - Both Catabolic and Anabolic Pathway

An amphibolic pathway is a metabolic pathway that comprises both anabolic and catabolic processes.  

B. Davis coined the term amphibolic pathway. A biochemical pathway, which involves both catabolism and anabolism is known as an amphibolic pathway.

An amphibolic pathway is the one which is used for both breaks down and synthesis of reactions. Krebs cycle is amphibolic because it provides the number of intermediates for the anabolic pathway. In this process, both catabolism and anabolism occurs.

Glucose is the main  substrate for respiration and it is only biomolecule that is oxidised during respiration. Although All types of  carbohydrates may used during restoration but these carbohydrates first converted into glucose before they are used for respiration.

Other substrates can also be used in

respiration but  they can not involved since beginning in respiration or not enered in first step of respiration.

Fat as Respiratory substrate  Fats are  broken down into glycerol and fatty acids . If fatty acids are used as respiratory substrate than it is transformed into acetyl CoA and than  enter into the respiratiry pathway. Glycerol enters into  pathway when it is converted into phosphoglyceric acid.

Protein as Respiratory substrate

 The proteins are decomposed into amino acids  by the enzyme  proteases. After the  deamination, each amino acid enters into  different steps of Kreb cycle on the baisis of their structure. These amino acids may also enters  within the Krebs’ cycle  in form of pyruvic acids  or acetyl CoA. 

It has been mentioned at erlier thar fatty acids  are broken down into acetyl CoA before the entering into  respiratory pathway when it is used as a substrate. But if any  organism needs to synthesise fatty acids, than acetyl CoA would be withdrawn from the respiratory pathway for it. In this way, we can say that  respiratory pathway involve both  breakdown and synthesis of fatty acids. Similarly, both the  breakdown and synthesis of protein also takes place when it is used as respiratory substrate.

👌👌Remember - In the respiration, substrates are broken therefore   respiratory process is considered as  catabolic process But it is a amphibolic pathway.