Question

2. What is necessary in an enzyme's active site in order for a symmetric molecule to react asymmetrically with the enzyme? Please provide an example of this phenomenon using an enzyme from the citric acid cycle. 3. Metabolic functions must occur with high efficiency to insure continued survival of the organism. Why is a process as complex as the citric acid cycle actually an economical way for cells to do their metabolic business? How does the citric acid cycle interact with other pathways that we have talked about in this class? Do such overlaps between the citric acid cycle and other pathways enhance or hinder overall metabolic efficiency?

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Answer 1

Ans. This is a perfect case of induced fit hypothesis, where the substrate bounds to the active site. As the active site is flexible certain conformational changes would occur for the binding to proceed these may be induced by temperature, pH and numerous other cascades. Adenylate kinase is a perfect example of induced fit model.

Ans. Citric acid cycle is considered as economical due to the fact that limited number of molecules would result in generation of large number of NADH and FADH molecules for providing energy. The NADH generated is widely utilised for oxidative phosphorylation in the electron transport chain. These two cycles in union would result in the formation of ATP molecules as a source of energy.