membrane stuff Flashcards
key stuff about membranes
what are cell surface membranes mainly comprised of?
phospholipids
why can phospholipids form bi layers?
as they have a polar head and a non polar tail
what is the function of cholesterol
regulates membrane fluidity
name two things glycoproteins and glycolipids do
.act as self antigens
.help join cells together
why is diffusion a passive process
as it only requires the energy of the particles themselves and no energy in the form of ATP
what is osmosis
osmosis-movement of water across a partially permeable membrane from high water potential to low water potential until dynamic equilibrium has been reached.
what are the units of water potential
Kpa
what is the highest water potential?
0Kpa
what is active transport?
the movement of partcles from a low to high concentration
why is active transport an active process?
As it requires energy in the form of ATP
how phospholipids arranged in the bilayer of a membrane?
the hydrophobic tails point inwards the hydrophillic heads point outwards
name three factors that affect rate of diffusion
temperature,surface area,diffusion distance
what happens to a red blood cell if it loses too much water
water leaves the cell and the cell shrinks
what happens to a red blood cell if it gains too much water
it undergoes haemolysis(bursts)
what is the function of cell surface membranes
they are a barrier between the cell and it’s enviroment
they control what substances can enter and exit the cell
how does the cell surface achieve it’s function
it’s partially permemable they let some molecuels through but not others.
name three ways substances can pass through a cell surface membrane
osmosis,diffusion and active transport
what is the function of channel and carrier proteins do in the cell membrane
allow large molecules and ions to pass through the membrane
either by facilitated diffusion or active transport
how does the phospholipid bilayer allow non-polar/hydrophobic molecules to pass through the bilayer
the centre of the bilayer is hydrophobic
so it doesn’t allow water soluble substances to diffuse through it
outline how carrier proteins carry out facilitated diffusion
a large molecule attaches to a carrier protein in the membrane
then the protein changes shape
this releases the molecule on the other side of the membrane
outline how channel proteins work
they form pores in the membrane for charged particles to diffuse through
name two factors affecting the rate of facilitated diffusion
the concentration gradient
the number of channel or carrier proteins
how are cells adapted for rapid exhange
by large number of channel/carrier proteins in their membrane
by having a large surface area
