There are 2 correct options for this problem.
1) They only speed up the chemical reactions. : True
Enzymes are biological catalysts. A catalyst lowers the activation energy of the reaction. When a reaction needs less energy to start, it occurs at a faster rate.
Many biological reactions that occur in our body are occurring at body temperature. The reactions would become very slow at this temperature . Therefore enzymes act a catalyst to speed up these reactions.
2) They act as catalysts, each for one specific reaction. : True
This option is true because as discussed above, enzymes are catalyst and their job is to speed up a chemical reaction. Enzymes have active sites where a particular substrate can bind during the reaction. Therefore a given enzyme acts a catalyst for a specific reaction only.
