Which of the following is true of an enzyme? mark all that apply.

it is a protein.
it is a catalyst.
it binds to many different substrates.
it is small compared to its substrates.

The answer is: It is a protein; It is a catalyst.

Enzymes are proteins and they act as catalysts in a cell. They increase the rate at which chemical reactions occur within the cell. After the reaction, they are not altered or consumed fully. An enzyme can act as a catalyst of the same chemical reaction multiple times.  

The answer would be true.