2.2 Enzymes are highly specific both in the reaction catalyzed and in their choice of substrates (i.e, reactants). 2.2.1 An enzyme usually catalyzes a single chemical reaction or a set of closely related reactions(side reactions leading to the wasteful formation of by-products rarely occur) 2.2.2 Enzymes exhibit various degrees of specificity in accord with their physiological functions(what of the following? ): Low specificity: some peptidases, esterases and phosphatases Intermediate specificity: hexokinase, alcohol dehydrogenases, trypsin. Absolute or near a bsolute specificity: Many enzymes belong to this group, and in extreme cases, stereochemical specificity is exhibited (i.e, enantiomers are distinguished as substrates or products ).2.2 Enzymes are highly specific both in the reaction catalyzed and in their choice of substrates (i.e., reactants). 2.2.1 An enzyme usually catalyzes a single chemical reaction or a set of closely related reactions (side reactions leading to the wasteful formation of by-products rarely occur). 2.2.2 Enzymes exhibit various degrees of specificity in accord with their physiological functions (what of the following?): Low specificity: some peptidases, esterases, and phosphatases. Intermediate specificity: hexokinase, alcohol dehydrogenases, trypsin. Absolute or near absolute specificity: Many enzymes belong to this group, and in extreme cases, stereochemical specificity is exhibited (i.e., enantiomers are distinguished as substrates or products)