Fluid Mosaic Model

Structure
—> hydrophilic phosphate head
—> 2 hydrophobic fatty acid tails
—> arranged in a bilayer with hydrophobic fatty acid tails pointing inwards
hydrophilic phosphate heads on the surface

Function
—> partially permeable - regulates movement of molecules across membrane by size and charge
—> allows small uncharged/non-polar, fat sociable molecules to dissolve and pass through the phospholipid bilayer by diffusion (down a concentration gradient)

Structure
—> only found in cell surface membrane
—> phospholipid with a carbohydrate chain attached to the phosphate head
—> carbohydrate chain points out of cell

Function
—> acts as a cell marker called an antigen
—> used by immune system to recognise cells as self or non-self

{the carbohydrates chain can contain different carbohydrates so can be different shapes to show self or non-self}

Structure
—> spans both layers of phospholipid bilayer

Function
—> makes membrane selectively permeable
—> channel proteins - aqueous/hydrophilic channels allow movement of charges and polar molecules by diffusion (down a concentration gradient)
—> carrier proteins - move molecules by diffusion (down a concentration gradient) + active transport (against a concentration gradient) BUT the protein has to change shape to allow this

Structure
—> spans one layer of phospholipid bilayer or associated to one of the surfaces of the bilayer

Function
—> transport of molecules across the membrane

Structure
—> only found in cell surface membrane
—> intrinsic protein with a carbohydrate chain attached
—> carbohydrate chain points out of the cell

Function
—> acts as a receptor for a chemical messenger to bind to
—> complementary in shape to the chemical messenger
—> allows cell to ‘communicate’ in cell signalling

Structure 
—> lipid molecule 

Function 
—> regulates fluidity of membrane by increasing rigidity when temperature increases 
—> provides support for the membrane and strengthens it 
—> prevents loss of ions