26.27. Bioelectric phenomena

Question 1

What is the resting potential?

Answer 1

• Electrical potential of a cell relative to its surroundings, when not stimulated / involved in passage of an impulse.
• Intracellular is always negative compared to extracellular

Question 2

What is the range of values of resting potential?

Answer 2

From -30 to -90 mV (depends on the cell)

Question 3

How is the resting membrane potential calculated?

Answer 3

Using microelectrodes connected to a voltmeter. Ground (reference) electrode placed outside of the cell and recording (active) electrode is inserted into the cell (or axon)

Question 4

Which ion is more concentrated inside the cell?

Answer 4

Potassium is the highest

Question 5

Which ions are more concentrated outside of the cell?

Answer 5

Sodium and Chloride ions

Question 6

What causes changes of the resting potential?

Answer 6

Flow of specific ions through the membrane

Question 7

What are the 3 types of transport of matter through the cell membrane?

Answer 7

1. Passive diffusion
2. Facilitated diffusion
3. Active transport

Question 8

What is the membrane permeability constant?

Answer 8

pm = Dm / d (m/s)
Dm : diffusion coefficient within the membrane
d : membrane thickness

Question 9

What is the partition coefficient formula?

Answer 9

k = cm1/cv1 = cm2/cv2 = constant
cm : concentration in the mb
cv : concentration outside the mb

Question 10

What is the partition coefficient?

Answer 10

Ratio of concentrations of a compound in a mixture of 2 immiscible solvents at equilibrium

Question 11

Aggregated permeability constant formula

Answer 11

p = k * pm

Question 12

What is the driving force of passive diffusion of particles?

Answer 12

chemical potential gradient

Question 13

What is the formula of the chemical potential gradient?

Answer 13

mu = mu0 + RT * ln (c)

mu0 : standard chemical potential

Question 14

What is the driving force of passive diffusion of ions?

Answer 14

Electrochemical potential

Question 15

What is the formula of the electrochemical potential?

Answer 15

mue = mu + zFQ
mu : chemical potential 
z : number of charges
F : faraday's constant
Q : electric potential (act phi)

Question 16

What are 4 properties of facilated diffusion?

Answer 16

1. Faster than passive diffusion
2. Selective
3. Can be inhibited selectively
4. Can be saturated

Question 17

What is active transport?

Answer 17

• Transport of molecules against their electrochemical gradient
• Uses energy : ATP driven (ATPase)

Question 18

What are the 3 types of active transport?

Answer 18

1. Uniport
2. Symport
3. Antiport

Question 19

What is the electric model of the membrane, if it was only a phospholipid bilayer?

Answer 19

A capacitor, alone

Question 20

What is the electric model of the membrane?

Answer 20

A capacitor, connected to resistor(s) in series. There are different resistors for different ions

Question 21

What is electric conductivity in the mb? (formula)

Answer 21

G = 1/R

Question 22

What is electric conductivity proportional to?

Answer 22

Proportional to permeability

Question 23

What is the formula of the specific conductivity of the membrane?

Answer 23

sigma = 1/RA