AQA BIOLOGY AS UNIT 1

1. THE PLASMA MEMBRANE
 Thisis the membrane foundonthe surface of animal cellsandjustinside the cell wall of plantcellsandprokaryoticcells
 The structure of all membranesisbasicallythe same-they`re composedof lipids(mainlyphospholipids), proteinsandcarbohydrates(usuallyattachedtothe
proteinsorlipids)
 It regulatesthe movementof substancesintoandoutof the cell
 Alsohasreceptormoleculesonit,whichallowittorespondtochemicalslike hormones
 in1972- fluidmosaicmodel was suggestedtodescribe the arrangementof moleculesinthe membrane
 inthe model,phospholipidmoleculesformacontinuous,doublelayer(bilayer)
 Thislayeris`fluid`because the phospholipidsare continuouslymoving-proteinmoleculesare scatteredthroughthe layer,like tilesinamosaic