social cells 2- channels

Question 1

what is passive transport?

Answer 1

diffusion through bilayer

diffusion through protein channels

facilitated diffusion- mediated by carrier proteins

Question 2

describe difference between faciliated diffusion to normal diffusion

Answer 2

• transport mechanism is specific: it will only bind to substances it is able to carry
• limited capacity: if high substance, it can only take a certain amount before it is full
• transport can be affected by competition: will be determined by the concentration of the substance and how well they bind

Question 3

what is active transport

Answer 3

carrying substances against the concentration gradient: required energy

Question 4

what are the 2 mechanisms of active transport?

Answer 4

• primary active transport: ATP is direct source, hydrolysis ATP
• secondary active transport: stored potential energy

Question 5

describe ion pumps

Answer 5

• cells have a continous leakage of ions
• pumps can transport ions against their concentration gradient

Question 6

3 types of ion pump, describe them

Answer 6

• uniporter: transports ions in one direction
• symporter: 2 ions in same direction, can also go the other way
• antiporter: able to pump ions in different directions across membrane

Question 7

examples of ion pumps

Answer 7

sodium potassium ATPase

glucose

calcium

Question 8

describe the sodium-potassium ATP-ase

Answer 8

3 sodium pumped out of cell against concentration gradient, in return bring 2 potassium int the cell against concentration gradient. This generates membrane potential of the cell

Question 9

what are ion channels

Answer 9

• proteins within the cell membrane
• specific ions

Question 10

4 types of ion channel

Answer 10

• ligand-gated ion channels
• voltage-gated ion channels
• leak channels
• stretch- activated channels

Question 11

describe ligand-gated channels

Answer 11

ligand causes change of conformation in channel which allows ion to move through

have a messenger (ligand) that binds to receptor/ion channel which causes the conformational change

can be intra or extracellular

Question 12

example of a ligand gated channel

Answer 12

GPCR- G protein coupled receptor
- ligand binds to the receptor which activates the G proteins in the cell

Question 13

describe voltage-gated ion channels and an example

Answer 13

affected by a potential difference across the membrane

resting state is closed channel

change in voltage which causes a conformational change in the channel

depolarisation of the membrane around the channel, the change in voltage here causes the conformational change in the channel which, makes it open

the flow of sodium causes a further change in the membrane potential of the cell which closes the channel and it goes back to resting state

example sodium channel

Question 14

describe leak channels and an example

Answer 14

• pore thorhg the membrane
• always open
• allow transport of ions along there concentrations gradient
  sodium leak channels

Question 15

describe stretch-activated channels and give an example

Answer 15

bilayer model- activated by change in tension of the membrane
tether model- either tethered to ECM or cytoskeleton, tension transmitted along which affects the tether so the channel is pulled open
- example epithelium sodium channel or calcium-activated potassium channel

Question 16

importance of ion channels

Answer 16

• muscle paralysis
• heart disease
• local anaesthetics

Question 17

definition of resting potential membrane

Answer 17

the potential across the membrane when there is no action potential being propagated

Question 18

describe the cell membrane potential

Answer 18

extracellular: high calcium, chloride and sodium
intracellular: high potassium

Question 19

example of channel that contributes to resting membrane potential

Answer 19

Na/K ATPase pump in skeletal muscle

Question 20

hyperpolarisation

Answer 20

change in cell membrane potential where it becomes more negative than resting membrane potential

Question 21

depolarization

Answer 21

change in cell membrane where it becomes less negative/more positive than resting membrane potential