Amphibolic pathway : Respiratory pathway is involved in both anabolism and catabolism, thus the respiratory pathway is an amphibolic pathway rather than as a catabolic one.
Respiration involves the breakdown of substrates. The respiratory process has traditionally been considered a catabolic process and the respiratory pathway as a catabolic pathway.
The intermediates of the respiratory pathway are withdrawn and used for the synthesis of the other substrates.
Fatty acids are usually broken down to acetyl-CoA before entering the respiratory pathway. here it is used as a substrate. But when the organism needs to synthesise fatty acids, acetyl CoA is withdrawn from the respiratory pathway for the synthesis of fatty acids. Hence, the respiratory pathway has both synthesis and breakdown of fatty acids.
Similarly, respiratory intermediates, are the link in the synthesis and breakdown of proteins too. Thus, it is amphibolic pathway.