ELM2: Ion channels 101

Question 1

What is a carrier/transporter protein?

Answer 1

A substrate binds to one side
Undergoes conformational change and substrate flipped to other side
Passive or activE

Question 2

What is an ion channel?

Answer 2

Continuous pathway
Passive

Question 3

What are some properties of ion channels?

Answer 3

Transmembrane
Selectively permeable
Opening controlled with gating

Question 4

What is meant by the selective permeability of ion channels?

Answer 4

Choose which ions can enter and exit
Some ions are filtered out by the selectivity filter

Question 5

What is the ion gradient of sodium?

Answer 5

Higher outside
Open causes depolarisation

Question 6

What is the ion gradient of potassium?

Answer 6

Higher inside
Open causes hyperpolarisation

Question 7

What is the ion gradient of chlorine?

Answer 7

Higher outside
Open causes depolarisation

Question 8

What is the ion gradient of calcium?

Answer 8

Higher outside

Question 9

What is the overall state of voltage gated ion channels?

Answer 9

Closed state until depolarisation

Question 10

What are the three types of voltage gated ion channels covered?

Answer 10

Calcium
Sodium
Potassium

Question 11

What is the structure of voltage gated potassium channels?

Answer 11

Tetramer of 4 subunits
Transmembrane proteins
Crosses membrane 6 times

Question 12

What is the selectivity filter?

Answer 12

Rings of charge to filter out anions

Question 13

How does the selectivity filter filter out ions of the wrong size?

Answer 13

1. Strips hydration shell from ion
2. Ion enters channel
3. Ion already in channel pushed through
4. Ion is perfect size to both fit and interact with oxygen molecules in the wall of channel and remove hydration shell

Question 14

What is the hydration shell?

Answer 14

Ring of water molecules around an ion in solution

Question 15

How do sodium channels open and inactivate?

Answer 15

1. Voltage centre in channel has positive charge
2. Depolarisation causes voltage centre to move and open channel
3. Sodium crosses membrane
4. Potential increases and becomes positive
5. Ball and chain structure swings and blocks channel

Question 16

How do the subunits of potassium channels become the channel?

Answer 16

Four copies of subunit translated from mRNA
Come together to form channel

Question 17

How do sodium and calcium subunits become the channel?

Answer 17

Single sodium or calcium alpha subunit translated from mRNA and 4 pseudosubunits fold to form channel

Question 18

What is the physiological significance of voltage gated sodium channels?

Answer 18

Cause excitatory phase of action potentials in neurons and skeletal muscle

Question 19

What is the physiological significance of voltage gated potassium channels?

Answer 19

Help repolarise neurons during second phase of action potential
Involved in inhibitory responses to neurotransmitters

Question 20

What is the physiological significance of voltage gated calcium channels?

Answer 20

Excitatory phase of action potentials in cardiac muscle
Triggers vesicular release of neurotransmitters
Muscle contraction

Question 21

Which channel is involved in drugs for high blood pressure

Answer 21

Calcium channel blockers
EG Verapamil and nifedipine

Question 22

What channel is involved in drugs to treat pain?

Answer 22

Calcium channel blockers
EG lidocaine

Question 23

What channel is involved in drugs to treat heart rhythm disorders?

Answer 23

Calcium sodium and potassium channel blockers

Question 24

What channel is involved in drugs to treat angina?

Answer 24

Calcium ion channels
EG Verapamil and nifedipine