04 Resting Potential

Question 1

2 What is the formula for salt?

Answer 1

NaCl

Question 2

2 Water molecules are nonpolar.

Answer 2

False

Question 3

2 What is an anion and cation?

Answer 3

Negatively and positively charged molecules respectively

Question 4

3 How thick is the lipid bilayer?

Answer 4

5 nm

Question 5

4 How is separation of charges responsible for potential?

Answer 5

Charges line up along the membrane and the rest of the fluid is electrically neutral. You only get the membrane potential right up against the membrane because the + and - charges line up on the membrane.

Question 6

4 What are the two basic properties that account for resting membrane potential?

Answer 6

1)Unequal distribution of key ions across the cell membrane. (like more sodium than potassium ions) 2) Differences in membrane permeability to these ions.

Question 7

5 How long does it take for charge to become evenly distributed after depolarization?

Answer 7

100 picoseconds or 10-10 seconds

Question 8

6 Hyperpolarization and what cause it?

Answer 8

Increase in potential (polarization). Membrane more negative than resting membrane potential. Reason: The extra K+ that go out of the channel because the gate is slow to close.

Question 9

8 How do Ions get across the membrane:

Answer 9

through pumps, channels and exchangers

Question 10

8 What is a gated channel?

Answer 10

A channel that is only open when it is bound by a specific molecule or ion.

Question 11

8 What are exchangers in a cell membrane?

Answer 11

A channel that will trade an ion from the cytosol with an ion outside the cell.

Question 12

8 Which pore is designed to maintain polarity across the cell membrane?

Answer 12

Na/K pump.

Question 13

8 Why is it that potassium ions are more free to move in and out of the cell, while sodium ions are not?

Answer 13

Potassium ions are free to move across many channels, while sodium relies on gated channels.

Question 14

8 How long does it take for ions to find gate and move through it?

Answer 14

Milliseconds

Question 15

11 How does diffusion work?

Answer 15

Molecules move from an area of high concentration to low concentration

Question 16

12 What does Ohm’s Law describe?

Answer 16

Describes ionic current flow across the membrane for a particular ion.

Question 17

14 What keeps the cell polarized?

Answer 17

Transmembrane potential

Question 18

15 What do you find mostly in the cytosol?

Answer 18

Potassium

Question 19

15 Considering that the cytosol has a lot of potassium ions (positively charged), how is it that the cytosol carries a negative charge?

Answer 19

Cytosol also contains many negatively charged proteins, phosphates, and chlorine anions.

Question 20

16 The equilibrium state for charged molecule (ions) is determined by what?

Answer 20

electrochemical gradient

Question 21

16 What is the Electrochemical equilibrium potential (Eion) ?

Answer 21

When electrical and concentration gradients exactly balance one another. Resulting in no net movement of a specific ion across the membrane.

Question 22

17-18 What are the concentration gradients for K+ and Na+? And what is the electrical gradient for K+ and Na+?

Answer 22

Concentation gradient for K+ is outward, for Na+ is inward. Electrical gradient: inward for both.

Question 23

17 It takes a large change in ion concentration to trigger depolarization.

Answer 23

False: a change of 10-5 mM of K is sufficient to change membrane potential from 0mV to - 80mV

Question 24

18 How thick is the cell membrane?

Answer 24

Membrane is less than 5nm thick

Question 25

22 Potassium is _____X more permeable than sodium.

Answer 25

40

Question 26

19 Each ion has its own equilibrium potential.

Answer 26

True

Question 27

21 How do you measure resting membrane potential?

Answer 27

Nernst equation

Question 28

21 What is the resting membrane potential of potassium ions?

Answer 28

-80mV

Question 29

21 What is the resting membrane potential of sodium ions?

Answer 29

61.54 mV

Question 30

22 Which way is chlorine going to move if the resting potential outside the cell is 65 mv and inside the cell is 65 mv?

Answer 30

Not moving anywhere because chlorine is the same value as the resting membrane potential

Question 31

23 What does the Goldman equation calculate?

Answer 31

Calculates the resting membrane potential based on the relative permeability of different ions

Question 32

23 What is the ratio of sodium outside the cell to inside the cell?

Answer 32

10: 1

Question 33

23 According to Goldman’s equation, what is the average resting membrane potential of a cell?

Answer 33

-65mV

Question 34

24 Concentration gradients are created and maintained by ______?

Answer 34

Active transporters: ATPase pumps; Ion exchangers; Co- transporters etc.

Question 35

26 What does the blood brain barrier limit?

Answer 35

Potassium

Question 36

26 ____________ have potassium pumps and channels that move K+ into the cell.

Answer 36

Astrocytes