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Flashcards in 12) Surface Electric Charge Of Cells Deck (18)
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1
Q

Origin of the electric charge of the cell surface

A

Cellular membrane is composed of
Proteins
Lipids
Hydrocarbons

The surface of the membrane builds up electric charge due to
Dissociation of atomic groups
Adsorption of ions from the surrounding fluid from surface membrane

2
Q

Electric charge of proteins

A

Adsorption is weak because of the hydration of protein molecules

Dissociation can be acidic or basic

3
Q

Proteins in acidic soloutions

A

The basic OH dissociates from the protein molecule

Protein cations are obtained

E+ HCl= E+ H20 cl-

4
Q

Proteins in basic solutions

A

Acidic H dissociated from the protein

Anions are obtained

e + NaOH= e_ Na h20

5
Q

Electric charge of lipids and hydrocarbons

A

Lipids and hydrocarbons have no dissociating atomic groups

The adsorption of ions prevails

Anions are adsorbed more readily than cations because their hydrate shell is thinner

6
Q

Potential determining ions

A

The ions which remain on the cell surface on dissociation

Are attached to cell surface by adsorption

7
Q

Counterions

A

Dissolve in the liquid phase due to dissociation

Remain in liquid phases due to adsorption

8
Q

Electric charge on native cell surface

A

The surface of intact cells in w medium with normal Ph builds up a negative charge

The surface change of cells indices the voltage gated ion channels mainly the sodium ones

9
Q

Electrical double layer definition and structure

A

The system of the surface charge and then neutralising charge of the counterions close to the surface

The screening charge consist of 2 layers

Stern adsorption layer
Diffuse layer 2

10
Q

Stern layer and the diffuse layer

A

The ions of the stern layer are attached to the surface by adsorption forces

The ions of the diffuse layer are attracted by the coulomb

11
Q

The gouy chapman model for the double layer

A

Approximations

Flat solid surface
In contact with ionic solution
Uniformly distributed electric charge on the surface

12
Q

Equilibrium of counterions

A

The electrochemical potential does not change with the distance x from the solid surface

13
Q

Equilibrium distribution of electrical potential

A

Additional assumption

The total charge of the system is zero

The electrical energy of the counterions is much less than its thermal energy

Electrical potential decays exponentially away from the surface

14
Q

The Debye screening length lander

A

The distance lander from the surface at which the potential is e times less than on the surface

Lander = root of ktę/z2e2c infinity

15
Q

Electrical potential inside thin membrane

A

If the electrical potential on both sides of the membrane are equal the potential inside the membrane has the same value as the outside

If the electrical potential on both sides are not equal then the potential inside changes linearly between 2 values

16
Q

Electrical potential inside thick membrane

A

The electrical potential inside the membrane changes nonlineerly even if the potential on both sides is the same

17
Q

The transmembrane potential

A

The potential difference between the inner and outer surface of the membrane

18
Q

Cell Morrison in an electrical field

A

Some of the counterions move with the cell

The interface between double layers is the slipping plane

The electrokinetic potential is the electric potential at the slipping plane

Also called zeta potential t