Enzymes act as catalysts in chemical reactions in cells. They are not used up themselves or altered in doing so.
They are used in digestion to break down large, insoluble food molecules, into smaller, water-soluble molecules.
if your choices are these then its D
a. changing one type of macromolecule to another
b. providing high-energy molecules that fuel cell processes
c. making up support structures in cells and tissues
d. supporting reactions involving energy transfer
