Origin of membrane potentials

Question 1

What occurs during a membrane potential?

Answer 1

Separation of opposite charges across the membrane

Different charges on each side of the membrane

Question 2

The plasma membrane of all cells are ……… electrically

Answer 2

Polarised

Question 3

Is the membrane itself charged?

Answer 3

No

Question 4

When can you tell if a membrane has more potential when comparing to other membranes?

Answer 4

More ions seen on other membranes compared to aother would mean it has more of a membrane potential

Question 5

What do excitable cells have the ability to create?

Answer 5

Membrane potential

Question 6

What is a resting membrane potential?

Answer 6

Constant in non-excitable cells, and in excitable cells at rest

Question 7

What is an Em due to?

Answer 7

Differences in concentration and permeability of key ions

Question 8

What is found in higher concentration in the extracellular environment due to evolutionary factors?

Answer 8

Na+ Cl-

Question 9

What ions are concentrated more in the intracellular compartment of the membrane?

Answer 9

K+, A-

Question 10

At resting potential the membrane is 100x more permeable to what?

Answer 10

K+ rather than Na+

Question 11

What are the two opposing forces acting on K+?

Answer 11

• The concentration gradient (tending to move K+ out of the cell)
• The electrical gradient (tending to move K+ into the cell)

Question 12

What happens to K+ when an equillibrium occurs?

What would the potential that exists at this equilibrium be called?

Answer 12

No further net movement

Equilibrium potential for k+ (Ek)

Question 13

What is the membrane potential of Ek and what do the charges symbolise?

Answer 13

-90mV

The polarity of the excess charge on the inside of the membrane

Question 14

Calculation for the Nernst equation

How can it be simplified for something in 37c?

Answer 14

Eion= RT/zF ln [ion]o/[ion]i

Eion=61log10[ion]o/i[ion]i

Question 15

What is the approximate resting Em potential for K+ and Na+ movement?

Answer 15

-70mV

Question 16

Why is Em not identical to Ek?

Answer 16

Slight inward leak of Na

Question 17

What benefit does the sodium potassium pump have on the Em?

Answer 17

Helps maintain the K+ and Na+ gradients across the membrane

Question 18

What is generates due to the sodium potassium pump exporting 3Na+ and 2K+ entering?

Answer 18

Hyperpolarizing current

Question 19

If the equilibrium potential is a higher number or lower umber what does this mean?

Answer 19

Lower- Sodium is more permeable

Higher- Potassium is more permeable

Question 20

What is the specialised use of Em in nerve and muscle cells?

Answer 20

Rapidly and transiently alter their membrane permeabilities in response to appropriate stimulation, resulting in fluctuations in Em.

Nerve impulses in nerve cells and triggering contraction in muscle cells