passive transport Flashcards
what is passive transport?
no energy required
what is diffusion?
the movement of a substance from an area of high concentration to an area of low concentration (down a concentration gradient)
how do living things use diffusion?
small, uncharged molecules use diffusion to cross the cell membrane (ex. oxygen, carbon dioxide)
when is diffusion useful and why?
over short distances- takes too long otherwise
what is osmosis?
the diffusion of a solvent across a membrane separating any two solutions which contain the same solvent (commonly thought of as the diffusion of water)
what does the direction of osmosis depend on?
the relative concentration of water molecules on either side of the membrane
what is osmoses affected by?
the concentration of solute in the solution
what is osmotic pressure?
the pressure created by water molecules as they try to reach equilibrium across a membrane
what is turgor pressure?
the outward pressure on the cell wall exerted by water in the vacuole of a plant cell (keeps the plant from wilting)
what is plasmolysis?
the shrinkage of the cell membrane away from the cell wall due to the loss of water (causes wilting)
what is facilitated diffusion?
diffusion across a membrane at a faster rate than would otherwise be expected
what causes facilitated diffusion?
assistance from membrane proteins
what are the two possible mechanisms for facilitated diffusion?
carrier proteins
channel proteins
carrier proteins
why can they change shape?
to allow certain molecules (ex. glucose) to cross
carrier proteins
what do they accept?
certain uncharged molecules only
