biological membranes part 2 Flashcards
biological membranes
selectively permeable
active transport
requires chemical energy (ATP); low to high
passive transport
does not require chemical energy (ATP); high to low
concentration gradient
where energy for passive transport comes from, the difference in concentration of a substance across space
diffusion
the process of random movement toward equilibrium
diffusion rate depends on
-size and mass of molecules or ions: smaller molecules diffuse faster
-temperature of the solution: higher temps equals faster diffusion
-density of the solution: low density equals faster diffusion
-concentration gradient: steeper gradient equals faster diffusion
-area and distance: short distance and large surface area equals faster diffusion
osmosis
diffusion of water; direction depends on the relative concentrations of water molecules
isotonic
equal solute concentrations
hypertonic
higher solute concentration outside cell
hypotonic
lower solute concentration outside shell
aquaporins
water can cross membranes through special channels
ion channels
channel proteins with hydrophilic pores
gated
can be closed or open to ion passage
facilitated diffusion
polar and charged molecules diffuse with concentration gradients, but facilitated by protein channels or carriers
channel proteins
integral membrane proteins that form a tunnel