why do you think a small amount of catalst or enzyme can have such a large effect on a chemical reaction?

Answer 1

There are two reasons that a catalyst works to improve the speed of reactions.

The first is that the catalyst/enzyme will lower the activation energy of the reaction by any of several mechanisms. The catalyst/enzyme may fix a molecule in a certain configuration that allows favorable collisions with other reactants, or it may stress a bond that allows it to break more easily, etc, etc,etc. By lowering the energy of activation, it increases the number of molecules that are above the threshold allowing the reaction to proceed

The second is that the enzyme or catalyst is not consumed in the reaction. So a small amount will go a long way.

Answer 2

A catalyst lowers the activation energy of a reaction. The activation energy is the energy needed for the reactants to form products. That's also why a reaction is sped up by a catalyst.

Answer 3

Because, by definition, a catalyst (an enzyme is a type of catalyst) is regenerated during a reaction. Therefore, it can continue to be reused in the reaction

Answer 4

because that's their job-- to catalyse that specific reaction