Describe catalyst and its function. Check all that apply. A catalyst is a substance that is not used up during a reaction. A catalyst affects the products obtained in the reaction. A catalyst does not change the pathway of the reactants to products in a way that reduces the activation energy and lowers the speed of the reaction. A catalyst does not affect the products obtained in the reaction. A catalyst changes the pathway of the reactants to products in a way that reduces the activation energy and speeds up the reaction. A catalyst is a substance that is used up during a reaction.