module 2: biological membranes Flashcards
what structure do cell membranes have
fluid mosaic
what are their permeability
partially permeable
how are phospholipids arranged
-bilayer
- heads hydrophilic tails hydrophobic
what does cholesterol do
-gives rigidity and stability
- at low temps- increases fluidity
function of proteins in the membrane
- channel proteins- allow small or charged particles through
- carrier proteins- transport molecules and ions across membrane by active transport or facilitated diffusion
- act as receptors
glycolipids and glycoproteins
-stabilise membrane
-site for drugs antibodies and hormones to bind
-receptors in cell signalling
-antigens
what does cell signalling allow
communication between cells
role of receptors in cell signalling
-have specific shapes
-different receptors are on different cells
-target cells respond to specific messenger molecule
-for drug reception
how to investigate cell membrane permeability with temperature
-5 equal sizes of beetroot
-rinse them to remove excess pigment
-place in 5 test tubes with water
-place in water bath at 5 degree intervals for same amount of time
-remove pieces of beetroot leaving liquid
-use colorimeter to assess how much pigment released
what is the effect of increasing temp on membrane permeability
higher permeability, phospholipid bilayer starts to move more and melt, proteins deform
what is the effect of changing the solvent on membrane permeability
-surrounding cells in solvent increases permeability e.g. ethanol
define diffusion
the net movement of particles from a high concentration to a low concentration
what type of molecules diffuse
small, non-polar
factors affecting rate of diffusion
-concentration gradient
- thickness of exchange surface
-surface area
-temperature
what proteins does facilitated diffusion use
carrier and channel
