Summary OCR A-Level Biology - Cell Membranes

membranes




Contents:
• Cell Membrane Structure
• Permeability
• Passive Movement
• Active Movement
• Osmosis

, cell membrane structure



said model
mosaic


fluid mosaic model describes the structure of the plasma membrane as a mosaic of

phospholipids;cholesterol;proteins;carbohydrates thatgives the membrane a fluid
character



fluid' area is due to phospholipid bilayer
mosaic area is made up of various proteins;carbohydrates;lipid molecules that

punctuate membranes



plasma membrane is permeable, defining the boarders cells and
partially of mostorganelles
-




partially permeable-

means the membrane controls the movement ofmaterials freely
into or outof the cell




phospholipide

arrange themselves into a sun-lonm thick bilayer
contains 1 molecule
glycerol
contains 2 fatty acids, which are hydrophobic so face inwards in the bilayer
contains phosphate
1 -
linked head group, which are hydrophilic so face outwards
in the bilayer



i
Pi

FATTY ACID


fATTY ACID




cholesterol

cholesterol is a lipid sits
that with phospholipids in the core the
of membrane,
bound to fatty acid hydrophobic tails


increase membrane rigidity in order to help maintain cell shape
not found in bacterial cell membranes