7) Passive Transport Of Ions

Question 1

Driving force for the passive transport of ions

Answer 1

Facilitated diffusion

Diffusion through pores and channels in membrane

Simple non mediated diffusion through bilayer

Question 2

Electrochemical potential

Answer 2

This is the sum of the chemical electrical and conc potentials

Question 3

Magnitude and direction of ion flux density

Answer 3

Directed from high to low values of electrochemical gradient

Various models are used to calculate ionic currents

Question 4

Facilitated diffusion

Answer 4

Ionophore is small hydrophobic molecules that shield the change of the ion and facilitate its diffusion

Ion binds to ioniphore
Ionophore ion complex forms and diffuses to other side of membrane

Question 5

Facilitated diffusion carrier example

Answer 5

Valinomycin

Ring shaped proteins that facilities the diffusion of potassium ions by electrochemical gradient

Question 6

Diffusion through ion pores and channels

Answer 6

Hey are transmembrane proteins and have hydrophilic and hydrophobic groups

Question 7

Pore example

Answer 7

Gramacidin

Is a pore forming anntibiotic
Helical peptide chain of 15 AA

Question 8

Electrically fates ion channel

Answer 8

Structure
Has 2 states open channel and closed channel

State is controlled by electric field and mechanical stress

Question 9

Ligand gated ion channels

Answer 9

Drawing
Of bilayer with mesh
Ligand attaches and then the mesh splits down the middle

Question 10

Mechanically gated channel

Light gated ions

Answer 10

Membrane proteins capable of responding to mechanical stress

Non specific is Na k and ca H
Limitation changes conformation and opens the passage

Question 11

Electro diffusion model

Answer 11

Aim is to determine the flux density of ion through membrane

Assumptions
Membrane is a continuous homogenous medium

Question 12

Ion flux density

Answer 12

J = cv = -cu du/dx

U is ion mobility
X is coordinate axis

Question 13

Nernst plank equation

Answer 13

J= -D ( dc/dx + d / dx. C)

Question 14

Goldman equation

Answer 14

P = lander D/d

P is permeability
d is membrane thickness

Question 15

Input and output of ion flux densities

Answer 15

J = Ji- je

Input - output

Question 16

Diffusion rate

Answer 16

The diffusion rate for cations through membrane of nerve desks is 10 times higher than that of the diffusion rate of anions

Due to layer of negative charge

Question 17

Generation of diffusion potential

Answer 17

Conditions

2 neutral volumes separated by a membrane

Diffusion potential depends on conc and mobility of ions

Question 18

Diffusion potential

Answer 18

Can be produced in bio membranes when there is damage

It usually reverts back to 0 bc then conc on both sides becomes equal

Question 19

Nernst equation

Answer 19

Potential difference depends on the ion concentration ratio on both sides

Question 20

Ion equilibrium in biological systems

Answer 20

In cells potassium is close to equilibrium

Sodium ions are far from equilibrium