Physiology- Membrane Transport

Question 1

Two properties which influence whether a particle can permeate the plasma membrane without assistance?

Answer 1

• solubility of particle in lipid

- size of particle

Question 2

Passive drive across membrane

Answer 2

Diffusion down concentration gradient

movement along an electrical gradient

osmosis

Question 3

Components of Fick’s Law of Diffusion

Answer 3

• magnitude of concentration gradient
• surface area of membrane across which diffusion is taking place
• lipid solubility of substance
• molecular weight of substance
• distance through which dissuasion takes place

Question 4

Fick’s Law

Answer 4

rate of transfer of molecules or atoms by diffusion through a unit area is proportional to concentration gradient

Question 5

What generates an electrical gradient?

Answer 5

difference in charge between two adjacent areas

Question 6

electrochemical gradient

Answer 6

the net effect of simultaneous electrical and concentration on an ion

Question 7

Osmosis

Answer 7

Net diffusion of water down its own concentration gradient through a selectively permeable membrane

Question 8

Does water move to an area of higher or lower SOLUTE conc by osmosis?

Answer 8

Higher

Question 9

Osmolarity

Answer 9

Concentration of osmotically active particles present in a solution

body fluids ~300mOsm/l

Question 10

Tonicity

Answer 10

the effect a solution has on cell volume

can be iso, hypo or hypertonic

no units

Question 11

Selective transport

Answer 11

carrier mediated or vesicular transport

Question 12

carrier mediated transport

Answer 12

substance binds to carrier, undergoing conformational change to transport substance

Question 13

Three important characteristics that determine the kind and amount of material transferred across the membrane

Answer 13

Specificity, saturation and competition

Question 14

Two forms which carrier mediated transport can take

Answer 14

facilitated and active

Question 15

Two forms of active transport

Answer 15

Primary and secondary active transport

Question 16

Primary active transport

Answer 16

Energy is directly required to move a substance against its concentration gradient

ATP driven

Question 17

Secondary active transport

Answer 17

Energy required but not directly used to produce uphill movement

transfer of solute across membrane coupled with transfer of ion which supplies driving force (usually Na+)

ion coupled

Question 18

Ratio of Na+ out to K+ in

Answer 18

3 Na+ in: 2 K+ out

Question 19

Na+-K+ ATPase

Answer 19

NA+-K+ pump which is a more complicated primary active transporter

Question 20

3 important roles of the Na+-K+ pump

Answer 20

1. establish Na+ and K+ conc gradients across plasma membrane of cells
2. regular cell volume by controlling solute conc inside cell
3. energy used to drive pump serves as an energy source for secondary active transport

Question 21

2 mechanisms in which secondary active transport occurs

Answer 21

Symport/ cotransport

antiport/ exchange/ countertransport

Question 22

symport

Answer 22

solute and Na+ move in the same direction

Question 23

antiport

Answer 23

solute and Na+ move in opposite directions (Na+ into cell)

Question 24

endocytosis

Answer 24

• pinching off membrane to engulf substance

- type of vesicular transport

Question 25

exocytosis

Answer 25

• vesicle fuses with plasma membrane and releases its contents into ECF
• type of vesicular transport