membranes
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width of membrane
7-10 nm
what is cell membrane made up of
• phospholipid bilayer • intrinsic and extrinsic proteins • glycoproteins • cholesterol
what did Gortner and Grendel do?
• study structure of cell membrane in different mammals • total SA of red blood cells measured in sample, compared to SA formed by single lipid layer extracted • lipid layer floated on water • single layer double total surface area, phospholipids fold over each other
what can get through phospholipid bilayer?
small, uncharged and lipid soluble molecules
why is it selectively permeable?
non-polar tails repel water soluble, large charged molecules
channel proteins
intrinsic - pores lined with polar groups, allows water soluble substances to pass through
carrier proteins
intrinsic - allows large polar molecules to pass through, molecules bind to protein and is released on other side of the membrane
what do extrinsic proteins do?
cell recognition form receptors cell signalling anchor cell components
what does cholesterol do?
associates with the kinked tails of unsaturated fatty acids - allows phospholipids to pack closely together and behave like a fluid (maintains membrane fluidity)
what is the fluid mosaic model?
Singer and nicholson = fluid mosaic structure fluid= all components can independently move mosaic = proteins float in phospholipids, no fixed arrangement or pattern