unassisted membrane transport

Question 1

what are the 2 ways by which molecules and ions can move across the plasma membrane passively and unassisted

Answer 1

diffusion across a conc. gradient OR movement along an electrical gradient

Question 2

state the Fick’s Laws of diffusion and what they refer to

Answer 2

they are the factors that influence the rate of net diffusion across a membrane: magnitude of conc. gradient, SA of membrane across which diffusion is
taking place, the lipid solubility of the substance, molecular weight of substance, distance through which diffusion must take place

Question 3

describe the relationships between the factors in Fick’s Laws and the rate of net diffusion

Answer 3

increase SA = increase diffusion
increase liquid solubility = increase diffusion
increase magnitude conc. gradient = increase diffusion
decrease molecular weight = increase diffusion
decrease distance = increase diffusion

Question 4

describe what the electrical gradient is and its relationship with ions

Answer 4

electrical gradient is the difference in charge between 2 adjacent areas, it promotes movement of ions towards area of opposite charge

Question 5

describe what an electrochemical gradient is and how it effects the plasma membrane

Answer 5

when a conc.(chemical) gradient and electrical gradient are working on an ion simultaneously, the net effect of this is called the electrochemical gradient
electrochemical gradients contribute to the electrical
properties of the plasma membrane

Question 6

describe what osmosis is

Answer 6

osmosis = net diffusion of water down its own conc. gradient through a selectively permeable membrane

Question 7

describe the movement of water across membranes, what area will it move to?

Answer 7

water will move by osmosis to the area with a higher solute conc.

Question 8

describe what osmolarity is

Answer 8

osmolarity = the conc. of osmotically active particles in a solution

Question 9

describe what tonicity is

Answer 9

tonicity = the effect a solution has on cell volume

Question 10

state the meaning of the terms iso-, hypo- and hyper tonic

Answer 10

isotonic = no change in cell volume
hypotonic = increase cell volume
hypertonic = decrease cell volume