Answer:
Proteins
Explanation:
Cell membranes are composed of a bilayer of phospholipids in which proteins are embedded. One of the major differences between the cell membranes of distinct cells is the presence of cell-specific proteins in them.
The cell membranes have specific enzymes based on the functions of the cells. The cell membranes of the cells that make the lining of the small intestine secrete various enzymes to assist in the chemical digestion of nutrients. Enzymes of ATP synthesis are present in the inner mitochondrial membrane of mitochondria and thylakoids of chloroplasts.
Glycoproteins that serve as recognition proteins impart distinct identity of the various cells of an organism so that the immune cells do not attack the self-cells. The cell membrane of various cells has different types of receptor proteins that serve as a binding site for specific neurotransmitters and hormones. Distinct channel proteins and pumps, connection proteins, etc also differ among different cell types.