Ion channels and sensors MCQs With Answer

Ion channels and sensors MCQs With Answer

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Introduction

Ion channels and sensors are central topics in Advanced Pharmaceutical Biotechnology, bridging physiology, pharmacology and biotechnological innovation. This set of MCQs is designed specifically for M.Pharm students to deepen their conceptual understanding and prepare for exams and research discussions. Questions cover structural features and gating mechanisms of major ion channels, electrophysiological techniques (patch-clamp variants, voltage clamp), quantitative concepts (Nernst potential, conductance, open probability), drug interactions and channelopathies, and biosensors used for ion and small-molecule detection (electrochemical, optical, ISFET, genetically encoded indicators). The items focus on applied knowledge for drug discovery, screening platforms and sensor design in pharmaceutical contexts.

Q1. What is the primary determinant of ion selectivity in most potassium channels?

  • The S4 voltage sensor segment
  • The selectivity filter composed of conserved amino acids in the pore loop
  • The cytoplasmic regulatory domain
  • The lipid composition of the membrane

Correct Answer: The selectivity filter composed of conserved amino acids in the pore loop

Q2. Which electrophysiological technique is best suited for measuring single-channel currents from isolated membrane patches?

  • Two-electrode voltage clamp (TEVC)
  • Whole-cell patch clamp
  • Single-channel patch-clamp (cell-attached or excised patch)
  • Extracellular field recording

Correct Answer: Single-channel patch-clamp (cell-attached or excised patch)

Q3. The Nernst equation is used to calculate:

  • The conductance of a channel at a given voltage
  • The equilibrium (reversal) potential for a single ion across a membrane
  • The rate of ion permeation through a multi-ion pore
  • The maximal open probability of a channel

Correct Answer: The equilibrium (reversal) potential for a single ion across a membrane

Q4. Which of the following is a genetically encoded fluorescent calcium sensor widely used for live-cell imaging?

  • Fura-2
  • Fluo-4
  • GCaMP
  • Rhod-2

Correct Answer: GCaMP

Q5. In voltage-gated channels, the S4 segment typically contributes to:

  • Forming the ion selectivity filter
  • Binding intracellular ligands
  • Sensing membrane potential through positively charged residues
  • Anchoring the channel to the cytoskeleton

Correct Answer: Sensing membrane potential through positively charged residues

Q6. An ISFET sensor detects ion concentration by measuring changes in:

  • Optical absorbance
  • Surface plasmon resonance
  • Gate voltage at the FET caused by ion-induced surface potential changes
  • Mass of adsorbed molecules on a quartz crystal

Correct Answer: Gate voltage at the FET caused by ion-induced surface potential changes

Q7. Open probability (Po) of an ion channel is best described as:

  • The single-channel conductance multiplied by membrane capacitance
  • The fraction of time a channel spends in conductive (open) states under given conditions
  • The number of channels expressed per cell
  • The total ionic flux through the membrane per second

Correct Answer: The fraction of time a channel spends in conductive (open) states under given conditions

Q8. Which sensor modality is most appropriate for real-time amperometric detection of a redox-active neurotransmitter like dopamine?

  • Ion-selective electrode
  • Amperometric electrochemical sensor with a carbon or metal electrode
  • Surface plasmon resonance sensor
  • Fluorescent pH indicator

Correct Answer: Amperometric electrochemical sensor with a carbon or metal electrode

Q9. In a patch-clamp experiment, replacing extracellular Na+ with an impermeant cation and observing a shift in reversal potential primarily tests:

  • Channel gating kinetics
  • Ion selectivity and permeability
  • Drug binding affinity
  • Membrane capacitance

Correct Answer: Ion selectivity and permeability

Q10. A classic signature of ligand-gated ion channels is:

  • Activation solely by changes in membrane voltage
  • Opening in response to binding of specific neurotransmitters or ligands
  • Permanent open state once synthesized
  • Exclusive expression in intracellular organelles

Correct Answer: Opening in response to binding of specific neurotransmitters or ligands

Q11. Which parameter describes how much current flows through a channel for a given driving force?

  • Reversal potential
  • Conductance (g)
  • Membrane resistance
  • Membrane capacitance

Correct Answer: Conductance (g)

Q12. In drug screening for ion channel modulators, automated patch-clamp systems primarily improve which aspect of the assay?

  • Single-molecule resolution
  • Throughput and reproducibility across many compounds
  • Theoretical modeling accuracy
  • Intrinsic ion selectivity of channels

Correct Answer: Throughput and reproducibility across many compounds

Q13. The Goldman-Hodgkin-Katz (GHK) equation is used to calculate:

  • Electrical coupling between neurons
  • Membrane potential considering multiple permeant ions and their permeabilities
  • The diffusion coefficient of ions in solution
  • The total number of ion channels in a membrane patch

Correct Answer: Membrane potential considering multiple permeant ions and their permeabilities

Q14. Which of the following is an advantage of genetically encoded fluorescent sensors over synthetic dyes?

  • They cannot be targeted to specific subcellular compartments
  • They allow long-term and cell-type-specific expression in living cells or organisms
  • They are always brighter than synthetic dyes
  • They have no photobleaching

Correct Answer: They allow long-term and cell-type-specific expression in living cells or organisms

Q15. Patch-clamp “whole-cell” configuration is especially useful for measuring:

  • Single-channel openings with picoampere resolution
  • Macroscopic currents from the entire cell membrane and intracellular dialysis
  • Extracellular field potentials in tissue slices
  • Optical properties of membrane proteins

Correct Answer: Macroscopic currents from the entire cell membrane and intracellular dialysis

Q16. In ion channel pharmacology, an allosteric modulator typically:

  • Blocks the pore by physically occluding it
  • Binds at a site distinct from the agonist binding site and alters channel function
  • Irreversibly phosphorylates the channel
  • Increases membrane cholesterol to change channel expression

Correct Answer: Binds at a site distinct from the agonist binding site and alters channel function

Q17. Which sensor principle relies on measuring changes in refractive index near a metal surface due to biomolecular binding?

  • Amperometry
  • Surface plasmon resonance (SPR)
  • Ion-selective field-effect transistor (ISFET)
  • Fluorescence resonance energy transfer (FRET)

Correct Answer: Surface plasmon resonance (SPR)

Q18. The Hill coefficient derived from ligand-response curves provides information about:

  • Single-channel conductance value
  • Cooperativity of ligand binding to receptor or channel complexes
  • Electrical capacitance of the membrane
  • Number of ions passing per unit time

Correct Answer: Cooperativity of ligand binding to receptor or channel complexes

Q19. Nanopore sensors detect analytes primarily by:

  • Measuring optical fluorescence emission from labeled molecules
  • Recording transient ionic current blockades as molecules translocate through a nanoscale pore
  • Measuring mass changes on a crystal microbalance
  • Detecting changes in magnetic resonance signals

Correct Answer: Recording transient ionic current blockades as molecules translocate through a nanoscale pore

Q20. Which factor most directly influences the time constant (tau) for channel activation or inactivation kinetics in simple kinetic models?

  • Membrane thickness
  • Transition rate constants between states (opening/closing rates)
  • Ambient room temperature only
  • Type of recording pipette used

Correct Answer: Transition rate constants between states (opening/closing rates)

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