Most of the membrane's diverse functions are carried out by
a)
proteins
b)
cholesterol
c)
phospholipids
d)
nucleic acids
e)
hormones

A) 
proteins

Cell membranes contain membrane proteins that  allows all the interaction that occurs within the cell. It makes the cell membrane selectively permeable because of its characteristics as being fluid or its fluidity which means to say that they can move freely within the lipid bilayer. The membrane proteins can also be stored in the lipid bilayer together with the enzymes. It cannot be denied that membrane proteins have a lot of functions based on its type. They can be integral proteins, peripheral proteins and lipid bound proteins. 

Biochemistry, it deals with the chemical constitution, the breakdown and the synthesis of plant and animal products.