Question

Metal cations may do all of the following except A. donate electron pairs to functional groups found in the primary structure of the enzyme protein. B. serve as Lewis acids in enzymes. C. participate in oxidation-reduction processes. D. stabilize the active conformation of an enzyme. E. form chelates with the substrate, with the chelate being the true substrate.

Short answer

Answer: (A) Donate electron pairs to functional groups found in the primary structure of the enzyme protein.

Step-by-step solution

Understand the roles of metal cations in enzyme function

Metal cations are positively charged ions that can play several roles in the function of enzymes. They can act as cofactors, help in catalysis, or stabilize enzyme structure.

Analyze each option

A. Donate electron pairs to functional groups found in the primary structure of the enzyme protein - Metal cations usually accept electron pairs, not donate them, so this statement is possibly incorrect. B. Serve as Lewis acids in enzymes - Lewis acids accept electron pairs, which can happen for metal cations in enzyme function. So, this statement is correct. C. Participate in oxidation-reduction processes - Metal cations can act as cofactors and participate in redox reactions. So, this statement is correct. D. Stabilize the active conformation of an enzyme - Metal cations can help in stabilizing the enzyme's structure, including the active site. So, this statement is correct. E. Form chelates with the substrate, with the chelate being the true substrate - Metal cations can form chelate complexes with the substrate, leading to an active enzyme-substrate complex. So, this statement is correct.

Identify the incorrect option

After analyzing all the options, Option A is the only one that is incorrect as it states that metal cations donate electron pairs to functional groups found in the primary structure of the enzyme protein, which is not their role. So, the answer is (A).