Electrophysiology of the Cell Membrane

Question 1

What are the major inorganic ions that carry electrical currents (across membrane)

Answer 1

Ca 2+ , Na + , K + , Cl − , and HCO3-

Question 2

What three integral membrane proteins are used for electric current flow

Answer 2

ion channels, electrogenic ion transporters and electrogenic ion pumps.

Question 3

what things are involded in hormone secretion, ionic homeostasis, osmoregulation, and regulation of muscle contractility.

Answer 3

channels proteins

Question 4

charge/lading is measured in?

Answer 4

coulombs

Question 5

what is z for Cl-?

Answer 5

z=-1

Question 6

what is e0?

Answer 6

unitary charge , 1.6022 × 10 −19

Question 7

( ε r)=?

Answer 7

dielectric constant

Question 8

( ℱ )=?

Answer 8

attractive electrostatic force

Question 9

why cant Na move from water to inside of membrane?

Answer 9

(high ε) to the interior of a phospholipid membrane (low ε) ~36 kcal/mole. This value is 60-fold higher than molecular thermal energy at room temperature.

Question 10

what is intracellular recording

Answer 10

The sharp tip of a microelectrode is gently inserted into the cell and measures the transmembrane potential with respect to the electrical potential of the extracellular solution, defined as ground (i.e., ψ o = 0).

Question 11

What is the Vm of a skelatal muscle cell?

Answer 11

-90mV

Question 12

what is E (E=Vm/a)

Answer 12

electrical field.

Question 13

Skeletal muscle cells, cardiac cells, and neurons typically have resting membrane potentials of approximately .. to …mV; smooth-muscle cells have membrane potentials in the range of … mV; and the V m of the human erythrocyte is only about .. mV. However, certain bacteria and plant cells have transmembrane voltages as large as ….

Answer 13

Skeletal muscle cells, cardiac cells, and neurons typically have resting membrane potentials of approximately −60 to −90 mV; smooth-muscle cells have membrane potentials in the range of −55 mV; and the V m of the human erythrocyte is only about −9 mV. However, certain bacteria and plant cells have transmembrane voltages as large as −200 mV.

Question 14

When are spectroscopic techniques used to meassure the Vm

Answer 14

very small cells such as erythrocytes, small intracellular organelles such as mitochondria, and fine processes such as the synaptic endings of neurons

Question 15

how do spectroscopic techniques work

Answer 15

cells or membranes are labeled with an organic dye molecule and the absorption or fluorescence of the dye is monitored

Question 16

what is another way of measuring Vm (not spectroscopic or microelectrode).

Answer 16

optically is to use cells that express genetically engineered voltage-sensing proteins that have been coupled to a modified version of the jellyfish green fluorescent protein (GFP).

Question 17

what does the optical method for measuring Vm benefit from

Answer 17

it can see that Vm changes are similar but delayed in the more distant neural processes inaccessible to the microelectrode.

Question 18

what 3 objects are needed for the fluorescent dye method?

Answer 18

light source
dichroic mirror
photodetector
(emmited red light changes with Vm

Question 19

what ois resting potential

Answer 19

steady value (Vm) when the cell is not undergoing active responses

Question 20

With what parameter does Vm have relationship?

Answer 20

Electrical field

Question 21

what are electrogenic transporters

Answer 21

transporters that can generate a current that sets up and electric potential accros the membrane.

Question 22

is the Na-K pump direct contribution to the Vm small or large?

Answer 22

small

Question 23

What happens if you switch CL to SO4

Answer 23

you eliminate the contribution of anions to Vm

Question 24

How is the Na-K pump responsible for Vm

Answer 24

indriect by generating and maintaining ion gradients

Question 25

WHat is the planar lipid bilayer

Answer 25

artificial cell membrane

Question 26

To what is the planar lipid bilayer similar intracellular recording or spectroscopic. and what is the main difference between PLB and the similar technieque

Answer 26

intracellular | both sides of the mebrane are accessible to manipulation

Question 27

Why does one add a suffienct amount of a nonelectrolyte to the side with lower KCL concentration (Planar Lipid Bilayers)

Answer 27

to ellimante osmotic flow

Question 28

What substance can you add to Planar Lipid Bilayer to eliminate osmotic flow.

Answer 28

mannitol | nonelectrolyte

Question 29

is the planar bilayer permeable or impermeable?

Answer 29

impermeable

Question 30

what are the minimal components for generating a Vm

Answer 30

impermeable membrane unequal ion solutions (ion gradient) ion-selective channels (conductance pathway)

Question 31

what do ion channels do for the membrane

Answer 31

a conductance pathway lowering the resistance

Question 32

what are diffusion potential

Answer 32

the membrane potential caused by , X diffuses down its concentration gradient (in planar-bilayer)

Question 33

what is simmilar to the diffusion potential at equilibrium

Answer 33

equilibrium potential ( E X )

Question 34

what gives the nernst equation

Answer 34

equilibrium potential ( E X )

Question 35

What are the two ways to predict Vm without the discovery of ion channels

Answer 35

is to measure the movemnt of a single ion species through the membrane. 2. summing up the currents carried by each species of ions present

Question 36

what is electrodiffusion?

Answer 36

process of ion permeation through the membrane

Question 37

what is the constant vield assumption

Answer 37

the electric field (=the change in voltage with distance) is constant.

Question 38

what is the Independence principle?

Answer 38

the movement of an ion through a membrane is independent from the movement of other ions

Question 39

Px=Dx*β/ a. | what are the parameters

Answer 39

px= permeabilty coeffiecient Dx is the diffusion coefficient in the mebrane a= the thickness of the membrane β is the membrane/water partition coefficient for the ion,

Question 40

what does the electrodiffusion model assume

Answer 40

homogenous membrane constant electric field ions move independently from one another a constant permeabilty coeffiecient.

Question 41

what laws do we use do calculate current of a single ion (with electrodiffusion model assumptions)

Answer 41

1. fick's law of diffusion 2. the movement of ions in an electric field ((electrophoresis) 3. oHMS LAW

Question 42

What is the goldman-hodgkin katz current equations a result of

Answer 42

1. fick's law of diffusion 2. the movement of ions in an electric field ((electrophoresis) 3. oHMS LAW

Question 43

what is the Goldman-Hodgkin-Katz (GHK) current equation,

Answer 43

the constant-field assumption applied to Nernst-Planck electrodiffusion

Question 44

what is Ix

Answer 44

the rate of ions moving through a membrane (ampere)

Question 45

to what does the GHK equation relate the current of ion X?

Answer 45

internal external concentration of X, transmembrane voltage and the permability of the membrane to X

Question 46

is the inward going current negative going current or positive going current

Answer 46

negative going current | in to the cell

Question 47

is the outward going current negative going current or positive going current

Answer 47

positive going current | out of the cell

Question 48

is inward flow of CL- inward or outward current?

Answer 48

outward, because current is always direction of positive charge.

Question 49

what is the reversal potential equal to?

Answer 49

Nernst potential (Ex)

Question 50

when Vm is more negative than Vrev what will cations do

Answer 50

move inward

Question 51

when is the GHK voltage equation or the constant-field equation is valid

Answer 51

when zero net flux flowing across the membrane

Question 52

when does VM equal Vrev?

Answer 52

at resting membrane potential.

Question 53

What happens with hypoklamia to the TWIK-1 K2P channel

Answer 53

α becomes larger, causes depolarization that can trigger cardiac arrhythmia leading to cardiac arrest

Question 54

what ion and cause has a high permeability to vertebate skeletal muscle cells

Answer 54

Cl, Cl − equilibrium potential in skeletal muscle is essentially equivalent to the resting potential

Question 55

what is an EMF

Answer 55

voltage source of a battery. | electromotive force

Question 56

what is the emf of an ion

Answer 56

the equilibrium potential

Question 57

what is the variable resistor of K

Answer 57

the conductance provided by K channels

Question 58

what is a capacitor

Answer 58

a device that is capable of storing charge

Question 59

what is the capacitor of a cell

Answer 59

the lipid bilayer

Question 60

what is capacitance

Answer 60

the magnitude of the carge stoped per unit potenial difference. in farads

Question 61

what is (ε 0 ), in capacitance

Answer 61

vacuum permittivity constant

Question 62

what is (ε r ) in capacitance

Answer 62

the relative permittivity (dielectric constant) of the medium between the two plates

Question 63

what is A in capacitiance formula

Answer 63

surface area (A) of one side of a plate

Question 64

are cell membrane potential sustained by a small or large separation of charge

Answer 64

small

Question 65

does Cl depolarize or hyperpolaryise

Answer 65

both in most cells depolarize | in skeletal cells hyper polarize

Question 66

what is the capacitative current?

Answer 66

the current that only flows when Vm is changing.

Question 67

how does a condensator (capacitor) produce current

Answer 67

when a voltage across a capacitor changes the capicator either loses or gains charge.

Question 68

what is the time constant

Answer 68

The time required for the voltage to fall to 37% of its initial value

Question 69

what is a square pulse

Answer 69

current or voltage is abruptly changed to a fixed value, held constant for a certain time, and returned to the original value.

Question 70

what does square pulse of V do to Im

Answer 70

2 brief spikes

Question 71

what does square pulse of I do to Vm

Answer 71

the voltage changes to a new value with a rounded time course determined by the RC value of the membrane.

Question 72

what is electrophoresis

Answer 72

the movement of ions in an electric field