Identify the molecules in the plasma membrane that provide basic membrane structure, cell identity, and membrane fluidity.

The main molecules present in the plasma membrane are phospholipids, those molecules are made of a polar, hydrophil end(glycerol with a phosphate group attached) and two non-polar, hydrophobe ends(two fatty acids rests). The cell identity is determined by proteins present in the membrane, a  very important type of protein that determines the identity of a specific cell is called marker. The membrane fluidity is reduced by a lipid with a ring structure, cholesterol, this molecule belongs to a class of biomolecules called steroids.