week 12: VGICs

Question 1

Q3. Which of the following correctly matches the ion with its VGIC?
A. Cav - Na⁺
B. Nav - K⁺
C. TRP - Ca²⁺ and Na⁺
D. Kv - Cl⁻

Answer 1

Answer: C. TRP - Ca²⁺ and Na⁺

Question 2

Q1. Which of the following ion channels is voltage-gated?
A. nAChR
B. Nav1.1
C. Aquaporin
D. CFTR

Answer 2

Answer: B. Nav1.1

Question 3

Q4. Which VGIC type is most diversified in the human genome?
A. NaV channels
B. CaV channels
C. Kv channels
D. TRP channels

Answer 3

Answer: C. Kv channels

Question 4

Q5. What kind of stimuli activate TRP channels?
A. Voltage only
B. Ligand binding only
C. Sensory stimuli like heat, touch, chemicals
D. Mechanical stretching only

Answer 4

Answer: C. Sensory stimuli like heat, touch, chemicals

Question 5

Q6. What is the structural basis for voltage sensitivity in VGICs?
A. Pore loop
B. S5 transmembrane helix
C. S4 transmembrane segment with positive charges
D. Cytoplasmic tail

Answer 5

Answer: C. S4 transmembrane segment with positive charges

Question 6

Q7. How do NaV and CaV channels differ structurally from Kv channels?
A. They are dimers
B. They are made of one large subunit with four homologous domains
C. They have fewer transmembrane domains
D. They lack a voltage sensor

Answer 6

Answer: B. They are made of one large subunit with four homologous domains

Question 7

Q8. The selectivity filter of VGICs is located in which region?
A. Between S1 and S2
B. Between S3 and S4
C. Between S5 and S6
D. At the N-terminal

Answer 7

Answer: C. Between S5 and S6

Question 8

Q9. Which channel has a selectivity filter that is 1000-fold more selective for its ion than other ions?
A. NaV
B. Kv
C. CaV
D. TRP

Answer 8

Answer: C. CaV

Question 9

Q10. What is the primary structure that allows VGICs to open in response to voltage changes?
A. The ligand binding domain
B. The ball and chain domain
C. S4 helix movement
D. β-subunit phosphorylation

Answer 9

Answer: C. S4 helix movement

Question 10

Q11. What does the “ball and chain” model explain?
A. Ion selectivity
B. Channel activation
C. Channel inactivation
D. Voltage sensing

Answer 10

Answer: C. Channel inactivation

Question 11

Q12. What is “deactivation” in the context of VGICs?
A. A permanent closure of the channel
B. Closing of the channel after the membrane potential returns to rest
C. Ligand-induced channel closure
D. Blocking by a toxin

Answer 11

Answer: B. Closing of the channel after the membrane potential returns to rest

Question 12

Q13. Which of the following is a function of β-subunits?
A. Form the pore of the channel
B. Determine ion selectivity
C. Regulate trafficking and localization
D. Directly bind neurotransmitters

Answer 12

Answer: C. Regulate trafficking and localization

Question 13

Q14. Which K+ channel type remains open for prolonged periods due to intracellular Ca2+?
A. A-type
B. Delayed rectifier
C. KCa channels
D. Inward rectifier

Answer 13

Answer: C. KCa channels

Question 14

Q15. Which regulatory mechanism can affect β-subunit function?
A. Phosphorylation
B. Oxidation
C. pH buffering
D. Glycosylation

Answer 14

Answer: A. Phosphorylation

Question 15

Q16. How do local anesthetics like lidocaine block NaV channels?
A. By binding to closed channels
B. By competing with Na+ for binding
C. By stabilizing the inactivated state via membrane fenestrations
D. By causing depolarization

Answer 15

Answer: C. By stabilizing the inactivated state via membrane fenestrations

Question 16

Q17. Why is NaV1.7 considered a target for pain therapy?
A. It is present in cardiac tissue
B. It is highly expressed in sensory neurons
C. It opens during repolarization
D. It regulates muscle contraction

Answer 16

Answer: B. It is highly expressed in sensory neurons

Question 17

Q19. Pregabalin acts on which VGIC-related structure?
A. TRP channel α-subunit
B. CaV channel β-subunit
C. NaV channel selectivity filter
D. Kv channel S4 domain

Answer 17

Answer: B. CaV channel β-subunit

Question 18

Q20. TRPV1 is activated by which compound?
A. Verapamil
B. Capsaicin
C. Lidocaine
D. Pregabalin

Answer 18

Answer: B. Capsaicin

Question 19

Q1. Which of the following is NOT a type of voltage-gated ion channel?
A. NaV
B. CaV
C. KV
D. nAChR

Answer 19

Answer: D. nAChR (it’s a ligand-gated channel)

Question 20

Q2. TRP channels are structurally related to VGICs but differ primarily in:
A. Their pore structure
B. Their selectivity filters
C. Their activation mechanisms
D. Their alpha subunits

Answer 20

Answer: C. Their activation mechanisms

Question 21

Q3. What structural component of VGICs confers ion selectivity?
A. The S1 domain
B. The cytoplasmic tail
C. The S4 segment
D. The S5-S6 pore loop

Answer 21

Answer: D. The S5-S6 pore loop

Question 22

Q4. What is the primary function of the S4 transmembrane segment in VGICs?
A. Drug binding
B. Ion selectivity
C. Voltage sensing
D. G-protein coupling

Answer 22

Answer: C. Voltage sensing

Question 23

Q5. What makes K+ channels 100-1000 times more selective for K+ over Na+?
A. Smaller pore size
B. Positive charge distribution
C. Selectivity filter structure
D. ATP binding domain

Answer 23

Answer: C. Selectivity filter structure

Question 24

Q6. What effect do accessory β subunits have on VGICs?
A. Form the ion pore
B. Control ion selectivity
C. Modify channel kinetics and expression
D. Block ion flow

Answer 24

Answer: C. Modify channel kinetics and expression

Question 25

Q7. Which mechanism explains the rapid closure of NaV channels after opening? A. Voltage deactivation B. Ball and chain inactivation C. ATP hydrolysis D. Ligand binding

Answer 25

Answer: B. Ball and chain inactivation

Question 26

Q8. What kind of VGICs are activated by intracellular calcium and remain open for long periods? A. T-type CaV channels B. Delayed rectifier K+ channels C. Ca2+-activated K+ channels D. P/Q-type CaV channels

Answer 26

Answer: C. Ca2+-activated K+ channels

Question 27

Q9. How do local anesthetics like lidocaine exert their effects on NaV channels? A. They bind to the extracellular side and block closed channels B. They block the pore from inside in a voltage-independent manner C. They bind to the inactivated state via fenestrations D. They degrade the channel protein

Answer 27

Answer: C. They bind to the inactivated state via fenestrations

Question 28

Q10. A mutation in which NaV channel leads to congenital insensitivity to pain? A. NaV1.4 B. NaV1.5 C. NaV1.7 D. NaV1.1

Answer 28

Answer: C. NaV1.7

Question 29

1. Functional States of VGICs Q1. Which of the following is NOT a functional state of voltage-gated ion channels? A. Open (activated) B. Inactivated C. Hyperactive D. Closed (resting)

Answer 29

✅ Answer: C. Hyperactive

Question 30

2. Ion Selectivity Q2. Ion selectivity in VGICs is primarily determined by: A. The β-subunit B. S4 transmembrane segment C. The cytoplasmic tail D. The S5-S6 pore loop (selectivity filter)

Answer 30

✅ Answer: D. The S5-S6 pore loop (selectivity filter)

Question 31

Q3. Why are K⁺ channels highly selective for potassium over sodium? A. They block Na⁺ with a membrane cap B. They use ATP to exclude Na⁺ C. The carbonyl oxygens in the selectivity filter precisely coordinate K⁺ D. K⁺ channels are gated by calcium

Answer 31

✅ Answer: C. The carbonyl oxygens in the selectivity filter precisely coordinate K⁺

Question 32

Q4. Which of the following is a function of the accessory (β) subunit in VGICs? A. Forms the ion pore B. Directly senses voltage C. Regulates trafficking and expression D. Controls neurotransmitter synthesis

Answer 32

✅ Answer: C. Regulates trafficking and expression

Question 33

Q5. Pregabalin acts on which component of the Ca²⁺ channel complex? A. α-subunit pore B. S4 voltage sensor C. β-subunit D. Selectivity filter

Answer 33

✅ Answer: C. β-subunit

Question 34

Q6. What causes voltage-gated ion channels to open? A. Binding of neurotransmitters B. Movement of the S4 segment due to depolarization C. Hydrolysis of ATP D. Calcium-induced phosphorylation

Answer 34

✅ Answer: B. Movement of the S4 segment due to depolarization

Question 35

Q7. The S4 transmembrane segment acts as: A. A ligand-binding site B. The inactivation gate C. A voltage sensor due to positive charges D. The ion selectivity filter

Answer 35

✅ Answer: C. A voltage sensor due to positive charges

Question 36

Q8. Which statement correctly describes Na⁺ and Ca²⁺ channels compared to K⁺ channels? A. They have fewer transmembrane domains B. They consist of a single large α-subunit with 4 domains C. They are tetramers of separate subunits D. They lack voltage sensors

Answer 36

✅ Answer: B. They consist of a single large α-subunit with 4 domains

Question 37

Q9. TRP channels are distinct from classic VGICs because they: A. Lack transmembrane domains B. Are activated by a wide range of stimuli including temperature and chemicals C. Have no ion selectivity D. Require ATP to function

Answer 37

✅ Answer: B. Are activated by a wide range of stimuli including temperature and chemicals

Question 38

Q10. How do local anaesthetics like lidocaine block Na⁺ channels? A. Compete directly with Na⁺ ions for the selectivity filter B. Bind to the closed state from outside the membrane C. Stabilize the inactivated state via membrane fenestrations D. Depolarize the membrane to prevent repolarization

Answer 38

✅ Answer: C. Stabilize the inactivated state via membrane fenestrations

Question 39

Q11. What makes local anaesthetics use-dependent blockers? A. They only act during synaptic transmission B. They bind better to frequently opening/inactivating channels C. They require ligand activation D. They phosphorylate the β-subunit

Answer 39

✅ Answer: B. They bind better to frequently opening/inactivating channels