Cell Membranes Flashcards
what is a plasma membrane
a membrane on the outside of a cell controlling what enters and leaves the cell
how are substances transported
osmosis, diffusion and active transport through the partially permeable membrane
what functions does the plasma membrane have
cell recognition (allows immune system to recognise it), cell signalling and substance movement
what are the functions of intracellular membranes
compartmentalisation, vesicles, substance movement
what is compartmentalisation
where the regions of a cell are split up this increases the rate of metabolic reactions
what is the fluid-mosaic model
represents the parts of a cell membrane the phospholipids being the fluid part as they continuously move and the proteins being the mosaic
why is a bilayer created
the hydrophobic tails face inwards to get away from the water with the heads facing the opposite way
why are water soluble substances stopped
the centre is hydrophobic making them repel water soluble substances
what does cholesterol do
located within the phospholipids it makes them pack tightly keeping the stability of the membrane
which proteins help ions into the cell
channel proteins and carrier proteins assist molecules that wouldn’t be able to get into the cell otherwise e.g. ions
what do glycolipids and glycoproteins do
stabilise membrane (hydrogen bonding), cell signalling (acts as an antigen), receptor cell
what are ‘membrane bound receptors’
proteins in the cell membrane which pick up signals
what does a complimentary receptor mean
the receptor is specific to the shape of the messenger molecule
what effect does a low temperature have on membranes
low temps-packed too closely together deforming carrier and channel proteins, very rigid due to low phospholipid movement
what effect does a normal temperature have on membranes
normal temperatures- allow phospholipids to gain kinetic energy and therefore it is less rigid and partially permeable
what effect does a high temperature have on membranes
a high temperautre increaes the kinetic energy too much as water begins to expand, therefore deforming the cell membrane making it more permeable
how does changing the solvent affect membranes
surrounding membranes in a solvent like ethanol would increase the permability as there strucutre would dissolve therefore deform
what is a passive process
it requires no energy
what is diffusion
net movement of particles from a high concentration to a low concentration
what molecules diffuse easiest
small non polar molecules
what process does water use
osmosis
what factors affect the rate of diffusion
concentration gradient, surface area,temperature and diffusion distance
what is facilitated diffusion
where larger/polar molecules use carrier and channel proteins, also a passive process, they use a molecule as a signal to allow the shape to change and open
what is active transport
`a molecule attaches to a carrier protein which changes its shape. it uses energy and goes against the concentration gradient. e.g. sodium-potassium pump (in plasma membranes)
