Parts of the cell membrane

Phospholipids

• A molecule made up of glycerol, two fatty acid chains and a phosphate group

• form the phospholipid bilayer of the cell membrane

• head of mol. is hydrophilic and tail is hydrophobic → they only allow small, lipid soluble molecules to diffuse across (flexible) membrane

Cholesterol

• Occurs within bilayer (animal only)

• adds strength

• very hydrophoobic so forms waterproof layer to prevent water loss from cells

• makes membrane less fluid in high temps.

• made in liver

proteins

• extrinsic proteins on surface bilayer provide mechanical support, some are enzymes

• ex. proteins often in conjunction with glycolipids - receptors

• protein channels extend across bilayer (water filled)

• carrier proteins bind to ions/mols and change shape to move mols across mem (active transport/facilitated diffusion)

• channels are specific, open and close and vary amount

Glycolipid

• carbohydrate and lipid

• recognition sites

• help membrane stability by forming hydrogen bonds with water surrounding each cell

• helps cells attach to one another

Glycoproteins

• carb chains attached to proteins

• recognition sites

• help cells attach to one another

• help cells recognise each other i.e lymphocytes to know self from non-self

Fluid-mosaic

• phospholipids are flexible and can move (fluid)

• proteins are embedded in bilayer (mosaic)