Lecture 3

Question 1

When K+ leak channels are placed…

Answer 1

• membrane becomes permeable to k+
• flow along an chemical gradient
• making inside more negative
• electrochemical gradient will attract k+ ions back in (opposite attracts)

Question 2

The intracellular and extracellular environements are in _______ & _________ disequillibrium

Answer 2

1. electrical
2. chemical

Question 3

why are ions unevenly distributed across cell membranes

Answer 3

• due to the selective permeability of the cell membrane to different ions
• based on the presence of ion channels and transporters in the plasma membrane

Question 4

give K+ concentrations

Answer 4

ICF: 140mM
ECF: 4mM

Question 5

give Na+ concentrations

Answer 5

ICF: 15mM
ECF: 145mM

Question 6

give Ca2+ concentrations

Answer 6

ICF: 0.001mM
ECF: 1.8mM

Question 7

give Cl- concentrations

Answer 7

ICF: 4mM
ECF: 115mM

Question 8

give P concentrations

Answer 8

ICF: 40mM
ECF: 2mM

Question 9

give protein concentrations

Answer 9

ICF: 4mM
ECF: 0.2mM

Question 10

What is the major contributor to cell negativity?

Answer 10

K+

Question 11

Define the resting membrane potential (RMP)

Answer 11

• the net charge difference between the intercellular fluid and extracellular fluid at rest
• due to the unequal distribution of ions on each side of the membrane that results in both electrical and concentration gradient

Question 12

membrane potential

Answer 12

measured from inside the cell relative to the outside

Question 13

What is the equilibrium potential

Answer 13

The potential where the electrical gradient opposes the concentration gradient and there is no net movement of the ion

Question 14

When Vm = Ex

Answer 14

Equilibrium is achieved

Question 15

The nernst equation calculates what

Answer 15

Equilibrium potential of an ion (Ex = (61/Z) log Iout/Iin)

Question 16

The GHK equations predicts what

Answer 16

• Predicts the membrane potential that results from all ions that can cross the membrane
• based on combined contributions of concentration gradients and relative membrane permeability for each ion

Question 17

Most cells are ______ times more permeable to k+ than NA+

Answer 17

40

Question 18

If the membrane potential becomes less negative than the resting potential the cell _________

Answer 18

Depolarizes

Question 19

If the membrane potential becomes more negative, the cell ______________

Answer 19

Hyperpolarizes

Question 20

What contributes to the negativity in the cell

Answer 20

1. Sodium potassium pump
2. K+ leak channels
3. Negatively charged proteins