Ch 7 - Movement of molecules across the CM

Question 1

what type of barrier is the cell membrane?

Answer 1

a lipid barrier

Question 2

what type of molecules can move across the cell membrane and what type of molecules cannot?

Answer 2

lipophilic molecules readily cross the CM.
- molecules that carry a charge do not. the CM is a diffusion barrier to these ions and polar molecules, they require a transmembrane channel or transporter to cross.

Question 3

what is the major role of the CM?

Answer 3

to serve as a diffusion barrier for selective movement of molecules in or out of the cell

Question 4

permeability

Answer 4

the ease with which a specific molecular species can cross a membrane

Question 5

how are molecules moved across the transmembrane?

Answer 5

either by diffusion or protein mediated transport

Question 6

diffusion: definition

Answer 6

process by which molecules intermingle because of their random thermal (Brownian) motion

the net movement of solute molecules from an area of hi concentration to low concentration

Question 7

Fick’s law of diffusion

Answer 7

the rate at which solute molecules can be determined:

J = DA(C1-C2)/X

Question 8

permeability constant

Answer 8

P = D/X

Question 9

what is the driving force of diffusion?

Answer 9

the concentration gradient! It provides the energy for net movement of molecules from one solution to another.

Question 10

how does the negative sign dealie work

Answer 10

when you are measuring the rate of diffusion of a molecular species from the high concentration solution, J has a negative sign because the concentration is deceasing

Question 11

factors that influence movement of ions across a membrane

Answer 11

1. concentration gradient
2. electrical gradient
3. permeability
   for any molecule to move in a solution, you must have a DRIVING FORCE

Question 12

Electrochemical equilibrium

Answer 12

the concentration gradient = the electrical gradient

requires ION selective semipermeable membrane

net ion flux by diffusion = 0

Question 13

the 3 major factors that influence the movement of ions across a cell membrane:

Answer 13

1. concentration gradient
2. electrical gradient
3. permeability

Question 14

what is the alignment of ions as a result of RMP?

Answer 14

negative ions on the inside and positive ions on the outside

Question 15

what can cause a change in permeability?

Answer 15

1. depolarization
2. hyperpolarization
3. permeability

Question 16

depolarization

Answer 16

when the cell (RMP) becomes LESS NEGATIVE

Question 17

hyperpolarization

Answer 17

when the cell (RMP) becomes MORE NEGATIVE

Question 18

permeability changes for an ion (and its effects on the change of RMP)

Answer 18

when the permeability for a specific ion increases, the RMP will move toward that ion’s equilibrium potential.
for K+ that will be hyperpolarizing
Na+ will be depolarizing

Question 19

what is important about Na+

Answer 19

it sets the action potential for a cell.