1/25: Cell Membrane, Membrane Transport, and Membrane Potential V

Question 1

What is a membrane potential?

Answer 1

Charge difference across the plasma membrane

Question 2

What is a membrane potential created by?

Answer 2

Unequal distribution of anions and cations across the cell membrane

Question 3

What is the source of energy in a membrane potential?

Answer 3

Charge separation

Question 4

What is the resting membrane potential?

Answer 4

Is the charge difference across the plasma membrane when the cell is at rest

Question 5

What is normal resting Vm (membrane potential)?

Answer 5

-70mV (varies by cell type)

Question 6

What does the sign in a Vm (membrane potential) represent?

Answer 6

The charge inside the cell

Question 7

What does the membrane potential create?

Answer 7

Electrical gradients for movement of ions into/out of cells

Question 8

What does the membrane potential do to ion channels?

Answer 8

Opens or closes gated ion channel

Question 9

What does membrane potential regulate?

Answer 9

Exocytosis

Question 10

What is an electrochemical gradient?

Answer 10

Two gradients for the passive transport of charged substances across the membrane

Question 11

What are the two types of membrane potentials?

Answer 11

1. Chemical gradient
2. Electrical gradient

Question 12

What is a chemical gradient?

Answer 12

Ions will move passively down concentration gradients

Question 13

What is an electrical gradient?

Answer 13

Ions will move passively down electrical gradient
*positive ion like Na or K they will move to the negative side of the membrane because opposites attract (move to a site of unlike charge)

Question 14

What does the strength of the electrical gradient depend on?

Answer 14

Valence of the ion and the magnitude of the membrane potential

Question 15

In which direction will there be net movement of K+?

Answer 15

Depends which is bigger

Question 16

When would there be no net movement of K+ through K+ channels?

Answer 16

Equal magnitude but opposite in direction

Question 17

What does equilibrium potential do?

Answer 17

Vm that creates a ΔE that is equal in strength but opposite in direction of the ΔC (ΔE-ΔC=0)
- electrochemical equilibrium
- no net ion movement through channels via facilitated diffusion

Question 18

What does the nernst equation calculate?

Answer 18

The equilibrium potential (E) when ion concentrations are known

Question 19

If Vm= -70mV, in which direction will there be net movement of K+ via facilitated diffusion?

Answer 19

Net flow out of cell; down EC gradient

Question 20

If Vm= -100mV, in which direction will there be net movement of K+ via facilitated diffusion?

Answer 20

Net flow into the cell

Question 21

If Vm= -90mV, in which direction will Cl- flow via facilitated diffusion?

Answer 21

Out of the cell

Question 22

At cell’s resting membrane potential, the equilibrium potentials for Na, K, Cl, and Ca are such that when an ion channel for one of these ions opens, the ions __________ their concentration gradient

Answer 22

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