Steric effects can influence catalysis in several ways. Firstly, they can affect the binding of substrates to the catalyst. For instance, bulky substituents on a substrate might prevent it from fitting into the active site of the catalyst, thereby reducing the reaction rate. Conversely, the catalyst itself might have bulky groups that can create a steric hinderance, blocking certain reactants from accessing the active site and thus enhancing the selectivity of the reaction.