Why are enzymes necessary?

A) to regard the rate of decomposition
B) to act as a catalyst in chemical reactions
C) to conserve the stored energy of a cell

The current thought on the structure of the cell membrane is: a. a static phosphate sandwich of lipids b. a fluid-mosaic of phospholipids and proteins c. a bilayer of proteins with static lipid molecules d. an impermeable bilayer of protein molecules e. a static and permeable phospholipid single layer