AQA Biology 3.5 the cell-surface membrane

Question	Answer
what is the cell surface membrane made up of?	phospholipid bilayer
why are phospholipids important in the membrane?	-hydrophilic heads point inwards to the cytoplasm -the outer layer has hydrophilic heads pointing out to interact with water outside the cells -hydrophobic tail point to the centre of the membrane.
what are the functions of the phospholipids?	-allow lipid soluble substances to enter and leave the cell -prevent water-soluble substances entering and leaving the cell -make the membrane flexible
what are the 2 types of proteins found on the cell surface membrane?	extrinsic and intrinsic
what do extrinsic proteins do?	give mechanical support or act as cell receptors for hormones
where to extrinsic proteins occur?	on the surface or only partly embedded in it
what are intrinsic proteins?	act as carriers to transport water-soluble molecules across membrane or are enzymes
ere are they found?	span the bilayer from one side to the other
what are the 6 main functions of these proteins?	-structural support -carriers transport water-soluble molecules -allow active transport though ion channels -recognition sites by identifying cells -help cells adhere -act as receptors
why is it called a FLUID mosaic model?	individual phospholipids can move relative to each other. gives membrane a flexible structure and is constantly changing shape
why is it called a fluid MOSAIC model?	the proteins embedded in the bilayer vary in shape, size and pattern so looks like a mosaic

Resource summary

	Created by Charlotte Hewson almost 9 years ago