Membrane transport MCQs With Answer provide B. Pharm students a focused review of mechanisms that govern drug movement across biological membranes. This concise, exam-oriented introduction covers passive diffusion, facilitated diffusion, active transport, carrier proteins, ion channels, uniport/symport/antiport, osmosis, electrochemical gradients, ABC transporters, P‑glycoprotein, and clinical implications for absorption, distribution, and drug–drug interactions. Each question emphasizes pharmacokinetic relevance—drug absorption, blood‑brain barrier penetration, ion trapping, and transporter-mediated resistance—so you build both conceptual depth and application skills. Perfect for revision before pharmacology and biopharmaceutics exams, these MCQs reinforce key mechanisms, kinetics (Km, Vmax), and transporter types essential for B.Pharm practice. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What best defines passive diffusion across a biological membrane?
- Movement of molecules from low to high concentration using ATP
- Movement of molecules from high to low concentration without energy input
- Transport of ions via ATP-dependent pumps
- Vesicular uptake of large particles
Correct Answer: Movement of molecules from high to low concentration without energy input
Q2. Which property distinguishes carrier-mediated facilitated diffusion from ion channels?
- Carrier-mediated transport is non-saturable
- Ion channels exhibit Michaelis–Menten kinetics
- Carriers show saturation at high substrate concentrations
- Channels consume ATP directly
Correct Answer: Carriers show saturation at high substrate concentrations
Q3. Which statement correctly describes primary active transport?
- Uses an electrochemical gradient established by another transporter
- Moves solutes down their concentration gradient without energy
- Directly uses ATP hydrolysis to move solutes against their gradient
- Occurs only by vesicular mechanisms
Correct Answer: Directly uses ATP hydrolysis to move solutes against their gradient
Q4. Secondary active transport is driven by which force?
- Direct ATP hydrolysis by the transporter
- Electrochemical gradient of one ion established by primary active transport
- Simple diffusion through lipid bilayer
- Endocytosis of extracellular fluid
Correct Answer: Electrochemical gradient of one ion established by primary active transport
Q5. Which of the following is an example of secondary active transport?
- Na+/K+ ATPase
- Glucose transport via GLUT1
- Sodium–glucose cotransporter (SGLT)
- Passive diffusion of ethanol
Correct Answer: Sodium–glucose cotransporter (SGLT)
Q6. What is the stoichiometry of the typical Na+/K+ ATPase per ATP hydrolyzed?
- 3 K+ out, 2 Na+ in
- 3 Na+ out, 2 K+ in
- 2 Na+ out, 3 K+ in
- 1 Na+ out, 1 K+ in
Correct Answer: 3 Na+ out, 2 K+ in
Q7. ABC transporters (e.g., P-glycoprotein) are characterized by which feature?
- They transport substrates by passive diffusion
- They use ATP to efflux drugs and xenobiotics
- They symport glucose with sodium
- They are voltage-gated ion channels
Correct Answer: They use ATP to efflux drugs and xenobiotics
Q8. Which pump is classified as a P-type ATPase?
- Glucose transporter GLUT4
- Na+/K+ ATPase
- P-glycoprotein (ABCB1)
- Sodium–glucose cotransporter (SGLT1)
Correct Answer: Na+/K+ ATPase
Q9. What defines an antiport transporter?
- Transport of two solutes in the same direction
- Transport of a single solute only
- Transport of two solutes in opposite directions
- Vesicular transport of macromolecules
Correct Answer: Transport of two solutes in opposite directions
Q10. Facilitated diffusion by carriers often follows which kinetic model?
- First-order irreversible kinetics
- Michaelis–Menten kinetics with a Vmax and Km
- Zero-order kinetics at all concentrations
- Henderson–Hasselbalch equation kinetics
Correct Answer: Michaelis–Menten kinetics with a Vmax and Km
Q11. Ion channels differ from carriers in that channels typically:
- Are highly selective and allow rapid ion flux when open
- Exhibit strong saturation at low ion concentrations
- Require ATP for each ion transported
- Bind substrate and undergo large conformational cycling like carriers
Correct Answer: Are highly selective and allow rapid ion flux when open
Q12. Paracellular drug absorption occurs through which route?
- Directly through the lipid bilayer of cells
- Through transcytosis vesicles within cells
- Between adjacent cells via tight junctions
- Only through active transporters
Correct Answer: Between adjacent cells via tight junctions
Q13. Osmosis is best described as the movement of:
- Solute particles from high to low concentration
- Solvent (usually water) from low solute to high solute concentration across a semipermeable membrane
- Ions across a membrane via ion channels
- Macromolecules by receptor-mediated endocytosis
Correct Answer: Solvent (usually water) from low solute to high solute concentration across a semipermeable membrane
Q14. Tonicity of a solution depends mainly on:
- Total solute concentration including penetrating solutes
- Concentration of non-penetrating solutes that affect cell volume
- The membrane potential only
- Temperature of the solution
Correct Answer: Concentration of non-penetrating solutes that affect cell volume
Q15. The reflection coefficient (σ) for a solute across a membrane equals zero. This means:
- The solute is completely impermeable to the membrane
- The solute is freely permeable across the membrane
- The membrane is electrically insulating
- The solute is actively pumped out of the compartment
Correct Answer: The solute is freely permeable across the membrane
Q16. The Nernst equation is used to calculate:
- The permeability coefficient of a solute
- The equilibrium potential for a single ion across a membrane
- The Vmax and Km of a transporter
- The osmotic pressure of a solution
Correct Answer: The equilibrium potential for a single ion across a membrane
Q17. At resting membrane potential, which ion most strongly influences the potential in many cells?
- Sodium (Na+)
- Calcium (Ca2+)
- Potassium (K+) due to K+ leak channels
- Chloride (Cl–) only
Correct Answer: Potassium (K+) due to K+ leak channels
Q18. Ion trapping (pH partition) causes weak bases to accumulate where?
- In alkaline compartments because they become neutral
- In acidic compartments because they become protonated and ionized
- Equally across all compartments regardless of pH
- Only inside lipid membranes
Correct Answer: In acidic compartments because they become protonated and ionized
Q19. Which drug property most increases passive transcellular absorption?
- High molecular weight and high polarity
- High lipid solubility (high partition coefficient)
- Strong positive charge at physiological pH
- Large hydrated radius
Correct Answer: High lipid solubility (high partition coefficient)
Q20. According to Fick’s law, which change will reduce passive diffusion flux across a membrane?
- Increasing membrane surface area
- Increasing the concentration gradient
- Increasing membrane thickness
- Increasing the permeability coefficient
Correct Answer: Increasing membrane thickness
Q21. What primarily limits paracellular drug absorption in epithelial barriers?
- Transporter-mediated efflux only
- Tight junction size and charge selectivity
- Active uptake by carriers
- Simple diffusion through lipid bilayer
Correct Answer: Tight junction size and charge selectivity
Q22. Which feature is NOT characteristic of the blood–brain barrier (BBB)?
- Tight junctions between endothelial cells
- High rate of transcytosis and fenestrated capillaries
- Low pinocytotic activity
- Expression of efflux transporters like P-glycoprotein
Correct Answer: High rate of transcytosis and fenestrated capillaries
Q23. P-glycoprotein (ABCB1) primarily affects drug therapy by:
- Enhancing passive diffusion into the brain
- Acting as an ATP-dependent efflux pump that reduces intracellular drug levels
- Functioning as a sodium-dependent cotransporter
- Directly metabolizing drugs to inactive forms
Correct Answer: Acting as an ATP-dependent efflux pump that reduces intracellular drug levels
Q24. Which statement correctly contrasts GLUT and SGLT glucose transporters?
- GLUT is secondary active; SGLT is facilitated diffusion
- Both require ATP directly to transport glucose
- GLUT mediates facilitated diffusion; SGLT is sodium-dependent secondary active transport
- Both are ion channels selective for glucose
Correct Answer: GLUT mediates facilitated diffusion; SGLT is sodium-dependent secondary active transport
Q25. A competitive inhibitor of a carrier-mediated transporter will typically cause which change in kinetics?
- Decrease Vmax without changing Km
- Increase Vmax and decrease Km
- Increase Km without changing Vmax
- No change in Km or Vmax
Correct Answer: Increase Km without changing Vmax
Q26. Uptake of low-density lipoprotein (LDL) particles into cells primarily occurs by:
- Simple diffusion through the lipid bilayer
- Receptor-mediated endocytosis via clathrin-coated pits
- Passive paracellular transport
- P-type ATPase activity
Correct Answer: Receptor-mediated endocytosis via clathrin-coated pits
Q27. Vesicular transport processes (endocytosis/exocytosis) are typically:
- Passive and energy-independent
- Saturable, selective, and energy-dependent
- Identical to carrier-mediated facilitated diffusion
- Responsible for small ion fluxes like Na+ and K+
Correct Answer: Saturable, selective, and energy-dependent
Q28. The electrochemical gradient that drives ion movement across membranes is composed of:
- Only the concentration gradient of the ion
- Only the membrane electrical potential
- Both the concentration gradient and the membrane electrical potential
- Neither concentration nor electrical components; it is purely osmotic
Correct Answer: Both the concentration gradient and the membrane electrical potential
Q29. Membrane transport processes influence pharmacokinetics by determining which of the following?
- Only the chemical stability of drugs in formulations
- Absorption, distribution, and elimination of drugs in the body
- Only the metabolic biotransformation pathways in the liver
- None of the ADME processes
Correct Answer: Absorption, distribution, and elimination of drugs in the body
Q30. Which process is characteristically stereospecific, saturable, and inhibitable by structural analogs?
- Passive diffusion through lipid bilayers
- Carrier-mediated transport via specific transport proteins
- Bulk flow of solvent across capillaries
- Nonselective ion channel permeation
Correct Answer: Carrier-mediated transport via specific transport proteins
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