Glucose is favourite sulphate for respiration as carbohydrates are first converted into glucose. Prior the to used for respiration, Fats are acetyl CO-A are broken down intob glycerol and fatty acid which is further degraded into acetyl Co-A, while protein is degraded into smaller units amino acids.

Respiratory process involves the breaking down of substrate is catabolic Proceses. Sometimes the fatty acid is required them synthesis of it occurs by withdrawing acetly Co-A. This synthesising phase is the anabolic process.

Thus, respiratory pathway involves the catabolic process (break down) and anabolic pathway synthesis of molecules using respiratory intermediates frant link, it is called as an amphibolic pathway.