cell transport Flashcards
(28 cards)
what is diffusion?
movement of particles from a region of high concentration to a region of low concentration along the concentration gradient
what is the concentration gradient?
difference in concentration between two regions
what molecules does diffusion allow to diffuse?
non-polar molecules
small molecules
lipid-soluable molecules
when does diffusion occur?
kinetic energy in molecules
concentration gradient
(no ATP needed)
what is facilitated diffusion?
passive transport via channel/carrier proteins
how do channel proteins carry out diffusion (properties)?
polar/charged molecules allowed through
can be gated
each protein is specific and will only allow one type of ion through
how do carrier proteins carry out diffusion (properties)?
particular molecule will attach to protein at binding site causing protein to change shape and release molecule through membrane
what molecules do carrier proteins allow to diffuse?
large molecules
what molecules do channel proteins allow to diffuse through?
polar/charged molecules
what does the graph look like for facilitated diffusion?
graph plateaus off
not directly proportional
what conditions do there have to be for facilitated diffusion to occur?
no concentration gradient
in a state of random movement due to kinetic energy
proteins present
(no ATP needed)
what is osmosis?
movement of water from an area of high water potential to an area of low water potential down a water potential gradient across a partially permeable membrane
what is water potential?
tendency for water molecules to enter or leave a solution by osmosis
what is the water potential of pure/distilled water?
0 kPa
how do you find the water potential of plant cells?
solute potential of cytoplasm + pressure potential
what happens to cells in HYPOTONIC solutions?
water potential of solution is higher
water moves into cell by osmosis
what happens to an animal cell when water moves into it?
lysis (cell bursts)
what happens to a plant cell when water moves into it?
turgidity (cell bursts)
what happens to cells in HYPERTONIC solutions?
water potential of solution is lower
water moves out of the cell by osmosis
what happens to an animal cell when water moves out of it?
crenation of the cell
what happens to a plant cell when water moves out of it?
cell is plasmolysed
what are isotonic solutions?
water potential value is the same in the solution and cell
(50% of cells are plasmolysed)
what is active transport?
movement of ions and other molecules across the membrane via carrier proteins
from an area of low concentration to high concentration against the concentration gradient
how does active transport via carrier proteins work?
molecules combine with specific protein
ATP transfers a phosphate group to carrier protein
protein changes shape and carries molecule across membrane into cell
molecule is released into cytoplasm
phosphate ion is released back to cytoplasm to recombine with ADP to make ATP
protein returns to original shape
