Enzymes speed up chemical reactions by

Here is the full statement: Enzymes speed up chemical reactions by LOWERING THE ACTIVATION ENERGY OF THE REACTION.

Explanation:

Enzymes are chemical substances that speed up the rate of chemical reactions. Activation energy on the other hand refers to the minimum amount of energy that reacting species must have in order for chemical reaction to occur.

Enzymes generally function by lowering the amount of activation energy that a particular chemical reaction needs to occur. For instance, if the activation energy needed for oxygen and hydrogen to react and form water is 1000 J, an enzyme used for the reaction can reduce the activation energy to 50 J, thus, making it easy for the reaction to occur more rapidly.