biological membranes
fluid mosaic model
newman and
molecules within membranes
phospholipid bilayer
intrinsic/ proteins
extrinsic/ proteins
glycoproteins
glycolipids
cholesterol
glycocalix
fluid because proteins are constantly moving
mosaic because phospholipid heads lined up look like a mosaic
roles of cell surface membrane
antigens to identify themselves
allow some things to get into cell
roles of internal membranes
things that affect membrane permeability
temperature
alcohol
low temperatures cause ice crytals which pierce membranes
below 0˚C
higher temperatures cause more kinetic energy in phospholipids and disrupt cell surface membrane
above 40˚C, phospholipids melt and membrane is damaged
proteins denature
dissolves cell membrane
cell signalling
nervous system
neurotransmitters sent between synapses of two nerve cells or nerve cell and muscle cell
glycoproteins and glycolipids act as receptors for signalling molecule
have specific shapes for signalling molecule to bind to it
diffusion across the membrane
simple diffusion
very small or non-polar/lipid-soluble molecules do this
molecules pass through the phospholipid bilayer
facilitated diffusion
specific molecules are helped by specific proteins to get across the membrane
done by polar molecules or ions
carrier or channel proteins do this
osmosis
water moves from an area of high water potential to an area of low water potential through a partially permeable membrane
movement of a substance from an area of high concentration to an area of low concentration