Transport Flashcards
diffusion
the passive movement of a molecule or ion down a concentration gradient from high to low concentration
main factors affecting rate of diffusion
concentration gradient
thickness of membrane
surface area
equation linking main factors of diffusion
SA x concentration gradient/ thickness of the membrane
other factors affecting diffusion
temperature
availability of ion channels and pores
size of diffusing molecule
lipid solubility
aquaporins
channel proteins that move water across the cell membrane, they have hydrophilic pores which allows water to pass by osmosis
osmosis
the net passive diffusion of water molecules across a selectively permeable membrane from a region of higher water potential to low
water potential
the tendency of water molecules to move out of a solution via osmosis
water potential is measured in
kPa/ kilopascals
pure water
0 tendency, has the highest concentration
adding a solute to water
gives water potential a negative value
higher concentration of solute=
stronger pull of water= lower water potential
solute potential
measures how easily water molecules move out of solution
more solute=higher conc=more tightly held molecules= lower tendency
pressure potential
water entering by osmosis expands the vacuole so pressure is put against the cell wall
makes the cell turgid
water potential equation
pressure potential+solute potential= water potential of cell
plasmolysis
the vacuole shrinks, and the cytoplasm draws away before becoming flaccid
flaccid
plant cells that have lost water and become limp and floppy
incipient plasmolysis
the external concentration is high and the cell loses enough water so that the membrane pulls away
hypotonic
wp of external>inside so water moves inside
hypertonic`
wp of internal>external so water flows outside
isotonic
external=inside, no net movement
hypotonic solution for animal and plants
animal= no cell wall so will experience cell lysis/ haemolysis in RBCS
plant= cell wall so will take in until pressure prevents it=turgid
facilitated diffusion
passive transfer of molecules or ions down concentration gradient across a membrane
completed by intrinsic protein
co transport
type of facilitated diffusion that brings molecules and ions across the membrane together by the same transport protein
stages of cotransport:sodium glucose
- glucose and 2 sodium ions bond to carrier protein which changes shape and deposits them inside the cell
- glucose and sodium separately diffuse through
- glucose passes into blood by FD
- sodium is carried out by active transport and potassium moves in
- more sodium moves from lumen bringing more glucose in also
phagocytosis
active process of the cell membrane engulfing large particles bringing them into the cell in a vesicle
eg granulocytes engulf bacteria, lysosome fuses with vesicle and enzymes digest
exocytosis
substances leave the cell having been transported through the cytoplasm in a vesicle
the cell membrane is constantly having portions…
removed or added through phagocytosis and exocytosis
pinocytosois
the same mechanism as phagocytosis but with the uptake of liquid and smaller vesicles
active transport
the movement of substances across a membrane against a concentration gradient using ATP from respiration
why is AT against a concentration gradient so important
it allows solutes to be accumulated in a cell giving it an appropriate balance
active transport happens through
carrier proteins
the rate of active transport is limited by
number and availability of carrier proteins
active transport processes
muscle contraction
nerve transmission
glucose reabsorption into kidney
mineral uptake into plants
active uptake of single molecule/ion
- ion combines with carrier protein
- atp transfers a phosphate group to carrier protein inside which changes shape and carries it across the membrane
- phosphate ion is released from carrier back to cytoplasm and recombines with adp
4.carrier protein returns to original shape
rate of uptake is reduced with the addition of
respiratory inhibitor, eg. cyanide
cyanide function in respiratory inhibition
prevents aerobic respiration and the production of ATP by inhibiting cytochrome oxidase so oxygen cannot bind
if more oxygen is available to cells
more active transport
