Cell Physiology L1

Question 1

Every cell is surrounded by a ______.

Answer 1

Membrane

Question 2

What is a membrane potential?

Answer 2

Difference between +ve (cation) and -ve (anions) in ICF and ECF

Question 3

Is the inside of the cell positive or negative?

Answer 3

Negative

Question 4

Is the outside of the cell positive or negative?

Answer 4

Positive

Question 5

The resting membrane potential (RMP) is a balance of (a), (b) and (c) for each ion.

Answer 5

(a) concentration gradient
(b) electrical gradient
(c) permeability

Question 6

The RMP is calculated by the ______ equation.

Answer 6

Nernst equation

Question 7

There are more _____ ions on the inside of the cell.

Answer 7

K⁺ ion

Question 8

There are more _____ ions on the outside of the cell.

Answer 8

Na²⁺ ion

Question 9

Resting cells are ____ permeable to K⁺= greatest influence on RMP

Rest V_m closest to E_K

Answer 9

Most

Question 10

What is permeability? How is it calculated?

Answer 10

Ability to move across a membrane

Is calculated by the Gold-Hodgkin-Katz equation

Question 11

What is electrically neutral membrane potential?

Answer 11

Has no potential

(eg. 10+ve and 10-ve in cell)

Question 12

What is potential membrane potential?

Answer 12

Imbalance- Potential for work to happen

(Eg. More +ve than –ve)

Question 13

What is separated charges membrane potential?

Answer 13

• Responsible for potential
• Membrane isn’t charged
• Row of +ve outside cell
• Row of –ve inside cell
• The rest of the cell is neutral

Question 14

What is separated charges accumulated along a plasma membrane? Membrane potential

Answer 14

Question 15

What is the magnitude of potential membrane?

Answer 15

Membrane C > Membrane B > Membrane A

The greater the separation of charges across the membrane, the larger the potential

Question 16

ICF is _____ negative than ECF

Answer 16

more

Question 17

What are the 3 key ingredients for a membrane potential?

Answer 17

1. Ion concentration gradient (Na²⁺/K⁺ pump)
2. Cell membrane (permeable)
3. K⁺ leak channels (ungated ion channels)

Question 18

What are the 2 types of ion channels?

Answer 18

1. Active
   
   • Keeps Na²⁺ out
   • Lets K⁺ in
2. Passive
   
   • Allows free flow

Question 19

What is the Nernst equation?

Answer 19

E = -RT . log [ion]out

zF [ion]in

E = the equilibrium potential

R = gas constant, T = temp, F= Faraday constant

z = ion valence (e.g. +1 for K⁺ and Na⁺, -1 for Cl^-)

At 37^oC simplifies to: 61 log [ion]out mV

[ion]in

Question 20

What is the RMP for K⁺? What does that mean and why?

Answer 20

Resting cells are permeable to K⁺ ions

• RMP close to Nernst potential for K⁺

E_K = 61 log [5 mM] = -90 mV

+1 [150 mM]

(if just K⁺ involved- most cells are -

Question 21

What is the RMP for Na²⁺? What does that mean and why?

Answer 21

E_Na = 61 log [150 mM] = +60 mV

+1 [15 mM]

(very different to RMP -70mV, Na²⁺ is not very permeable