movement of molecules Flashcards
1
Q
define osmosis
A
water diffuses across semi-permeable membranes from an area of higher water potential to an area of lower water potential until a dynamic equillibrium is established
2
Q
define faciliated diffusion
A
- passive process
- specific channel or carrier proteins with complementary binding sites transport large and / or polar molecules / ions (not soluble in hydrophobic phospholipid tail) down concentration gradient
3
Q
define simple diffusion
A
- passive process requires no energy from ATP hydrolysis
- net movement of small, lipid soluble molecules directly through the bilayer from an area of high concentration to an area of lower concentration (down a concentration gradient)
4
Q
explain how channel and carrier proteins work
A
channel: hydrophilic channels bind to specific ions = one side of the protein closes and the other opens
carrier: bind to complementary molecule =conformational change releases molecule on other side of membrane; in faciliated diffusion = passive process; in active transport = requires energy from ATP hydrolysis
5
Q
define active transport
A
- specific carrier protein transports molecules / ions from area of low concentration to an area of higher concentration (against gradient)
- active process: ATP hydrolysis releases phosphate group that binds to carrier protein, causing it to change shape
6
Q
define endocytosis
A
- bulk transport of material into a cell, active process
- two types:
phagocytosis: uptake of solid particles, cell membrane forms pseudopods which fuse together forming a vesicle
pinocytosis: uptake of liquids, cell membrane invaginates to form vesicle
7
Q
define exocytosis
A
- bulk transport of material out of a cell, active process
- reverse phago / pino cytosis
- vesicles fuse with cell membrane and contents are released out of cell
8
Q
name 5 factors that affect rate of diffusion
A
- temperature
- diffusion distance
- surface area
- size of molecule
- difference in concentration (steepness of gradient)
