Describe how protein functional groups can act as acid and base catalysts. How is it possible for a single amino acid side chain to function as both?

By changing the transition state and pH of the medium

Explanation:

Enzymes are proteins that bind to their corresponding substrates at their active sites in order to form complexes that catalyze specific chemical reactions. A key feature of this process is the fact that both acid and base catalytic activities may be combined in the same reaction. The acceleration in the velocity of the enzymatic reaction due to the addition of acids and bases is known as acid–base catalysis, where the acid or base is not consumed during the reaction. For example, enzymes can partially transfer a proton to the medium, thus changing the transition state of the chemical reaction and also decreasing its pH.

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