Exemplar Problems

Question:

Discuss “The respiratory pathway is an amphibolic pathway.”

Answer:

The statement “The respiratory pathway is an amphibolic pathway” refers to the dual role of the respiratory pathway in both catabolic and anabolic processes. In biochemistry, an amphibolic pathway is one that can be used for both breaking down (catabolism) and synthesizing (anabolism) molecules. The respiratory pathway, primarily involving the process of cellular respiration, perfectly illustrates this concept:

1. Catabolic Aspect: In the catabolic aspect, the respiratory pathway involves the breakdown of organic molecules, primarily glucose, to produce energy. This process includes glycolysis, the Krebs cycle, and the electron transport chain, where glucose is oxidized to carbon dioxide and water, releasing energy that is captured in the form of ATP.

2. Anabolic Aspect: The intermediates produced in the respiratory pathway, particularly during the Krebs cycle, serve as precursors for the biosynthesis of various biomolecules, marking its anabolic aspect. For example:

• Amino Acid Synthesis: Some of the intermediates are used as precursors for the synthesis of amino acids.

• Nucleotide Synthesis: Certain intermediates provide the carbon skeletons needed for the synthesis of nucleotides.

• Lipid Synthesis: Acetyl-CoA, an intermediate in metabolism, is a key precursor for fatty acid synthesis.