In a typical human cell, what fraction of the plasma membrane by mass is protein?

1. For a typical human cell, protein accounts for about 50 percent of membrane composition by mass. 2. Lipids of all types account for about 40 percent, and carbohydrates make up the remaining 10 percent. 3. So 40 percent is the lipid share and 10 percent is the carbohydrate share, not the protein share. 4. These proportions vary between different cell membranes, but 50 percent is the typical human cell figure. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 5 "Structure and Function of Plasma Membranes", section 5.1 Components and Structure_