Phospholipid bilayer

The cell membrane or plasma membrane is made up of a phospholipid bilayer

At its most basic, the phosphilipid bilayer consists of two layers (bi) of molecules of phospholipids 

Liquid/fluid, hydrogen bonding holds the two layers together 

Induvidual phospholipids and unanchored proteins can move through the membrane 

Saturated fatty acids make the membrane less fluid than unsaturated fatty acids 

Warm temperatures make the membrane more fluid than cold temperatures

Cell membranes contain: 

Phospholipid bilayer 

transmembrane proteins 

interior protein network 

Cell surface markers for example: glycolipid and glycoprotein

Image of phospholipid bilayer

Channel proteins- transmembrane proteins involved in transport across the membrane 

Glycoproteins- protein molecules with polysaccarides attached

Glycolipids- lipid molecules with polysaccarides attached

Membrane proteins have various functions: 

transporters

enzymes

cell surface receptors

cell surface identity marker

cell to cell proteins

attachement to the cytoskeleton