The cell membrane is a selectively permeable bilayer composed of phospholipids, proteins, and carbohydrates. Phospholipids form a bilayer with hydrophobic tails facing inward and hydrophilic heads facing outward. Embedded and peripheral proteins carry out important functions like transporting molecules through the membrane. The membrane controls what enters and exits the cell.

1. cell (plasma)
membrane
selectively
permeable
phospholipids
bilayer
proteins
transmembrane
(integral) proteins
peripheral proteins
transport proteins
carbohydrates
glycoproteins
cholesterol
polar molecules
non-polar
molecules
hydrophobic tail
hydrophilic head
protein channels
protein pumps
(permeases)
antigens