1.4 Flashcards
what is diffusion
the movement of particles from a region o f higher concentration to a region of low concentration - results in the random motion of particles
what are the two types of diffusion
simple and fascilitated dissuasion
how is movement across a partially permeable membrane affected
temperature - molecules diffuse faster at high temp
surface area - increase in SA allows more molecules to diffuse
size of particles - smaller molecules diffuse faster
concentration gradient of diffusing particles - the bigger the gradient the faster the diffusion
where does simple diffusion occur
in a gas or liquid medium and only requires a concentration gradient - occurs in both living and non-licign systems
when does simple diffusion not work
if molecules are too big or if they are charged such as ions and repelled by hydrophobic tails
what is facilitated diffusion
is a similar process to simple diffusion, it requires a channel protein or carrier proteins which are specific to the molecules being transported across the plasma membrane.
eg chloride ion channels that only allow facilitated transport of chloride ions
what is osmosis
the passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration across a partially permeable membrane
what solution does water move by
osmosis from hypotonic solution to the hypertonic solution
what happens in a hypotonic solution
there is a high water potential outside and Lower inside, osmotic uptake of water which can lead to bursting
what happens in an isosmotic solution
there is an equal water potential outside and inside so there is no net movement of water
what happens in a hypertonic solution
there is a low water potential outside and a high potential inside
osmotic loss of water, causing shriveling
what is important during medical procures
that tissues and organs are kept in solution that maintain the cells in a state as close to normal structure as function as possible
What is active transport
the movement of particles across membranes, requiring energy in the form of ATP, against a concentration gradient from a region of low concentration to one of a higher concentration
give an example of an active transport
the sodium -potassium pump
important in the nervous system for the maintenance of resting potential in neurons
summarise the sodium potassium pump
when the pump is open to the inside of the axon, three sodium ions enter to the pump and attach to their binding sites
the ATP donates a phosphate group to the pump
causing a change to the protein to change the shape expelling the sodium to the outside
Then, two potassium ions from outside enter and attach to their binding sites
the binding of K+ leads to the release of the phosphate which causes the pump to change shape again so that it is only open to the inside of the axon
k + is released inside
Na+ can now enter the pump again
