Resting membrane potential

Question 1

What is meant by membrane potential?

Answer 1

Magnitude of electrical charge that exists across a plasma membrane
inside relative to outside

Question 2

How is the membrane potential measured?

Answer 2

Microelectrode penetrates cell membrane
connected to voltmeter
all in a conducting solution

Question 3

What is a cell’s normal membrane potential at rest?

Answer 3

Negative

Question 4

What are the units of membrane potential?

Answer 4

mV

Question 5

What are the two requirements of producing a membrane potential?

Answer 5

Asymmetric distribution of ions across plasma membrane

Selective ion channels

Question 6

What is the open channel of channel proteins filled with?

Answer 6

Water

Question 7

Which ions can flow through an open ion channel?

Answer 7

The specific ion that the channel protein is for

Question 8

How do ions move through open ion channels?

Answer 8

Move through open ion channel in both directions

but net flow is down the electrochemical gradient of the ion

Question 9

What ion is the plasma membrane most permeable to? Why?

Answer 9

Potassium

open potassium ion channels are more common than that for other ions

Question 10

What is the concentration gradient for potassium ions across the plasma membrane?

Answer 10

Higher intracellular concentration than extracellular

Question 11

What is the electrical gradient for potassium ions across the plasma membrane?

Answer 11

For it to move to inside the cell from outside the cell

Question 12

How do potassium ions move across the plasma membrane?

Answer 12

Na+ K+ ATPase actively transports potassium ions into the cell
they then diffuse out of the cell through open potassium ion channels

Question 13

When does potassium stop moving across the plasma membrane?

Answer 13

When chemical and electrical gradients of potassium ions are opposite and equal

Question 14

What is the resting membrane potential?

Answer 14

The negative charge inside the cell compared to outside the cell
when potassium ions stop moving across the plasma membrane

Question 15

What makes the inside of cells negatively charged?

Answer 15

Contain anions

e.g. phosphate, bicarbonate etc.

Question 16

What is the equilibrium potential?

Answer 16

The membrane potential when the electrical and chemical gradients are opposite and equal
so there is no net flow of that ion

Question 17

How is the equilibrium potential for an ion calculated?

Answer 17

Nernst equation

Question 18

What does the equilibrium potential of an ion depend on?

Answer 18

Its charge

Its intracellular and extracellular concentrations

Question 19

What are Ek and ECl relatively?

Answer 19

Negative

Question 20

What are ENa and ECa2+ relatively?

Answer 20

Positive

Question 21

If the plasma membrane was permeable to absolutely only potassium ions, what would the resting membrane potential be?

Answer 21

Ek

Question 22

Is the normal resting membrane potential equal to Ek?

Answer 22

No

it’s less negative

Question 23

Why is the normal resting membrane potential less negative than Ek?

Answer 23

Because the plasma membrane is also somewhat permeable to other ions
e.g. sodium
calcium
moves the membrane potential a bit closer to their E values, hence less negative

Question 24

The normal resting membrane potential is closest to the equilibrium potential of which ion? Why?

Answer 24

Potassium

because plasma membrane is most permeable to potassium ions

Question 25

What type of cell has a resting membrane potential very close to Ek? Why?

Answer 25

Skeletal muscle cells

very rich in open potassium ion channels

Question 26

What type of cell has a resting membrane potential that’s almost 0? Why?

Answer 26

Red blood cells

have fery few open potassium ion channels