Transport models in biopharmaceutics MCQs With Answer

Transport models in biopharmaceutics are essential for understanding how drugs move across biological barriers and reach their site of action. This brief quiz collection is designed for M.Pharm students to reinforce core concepts such as passive diffusion, carrier-mediated transport, permeability coefficients, and common in vitro models like Caco-2 and PAMPA. Questions emphasize quantitative interpretation of flux, Fick’s laws, partitioning behavior, unstirred water layers, and experimental setups such as Franz diffusion cells. By working through these targeted MCQs you will strengthen your ability to predict drug absorption behavior, choose appropriate analytical models, and interpret permeability data — skills critical for formulation development, bioavailability assessment, and regulatory biopharmaceutics.

Q1. Which mathematical law most directly relates diffusive flux to concentration gradient in passive transport?

• Higuchi equation
• Noyes-Whitney equation
• Fick’s first law
• Michaelis-Menten equation

Correct Answer: Fick’s first law

Q2. In the context of membrane permeation, the partition coefficient primarily influences which term in the permeability equation P = (KD)/h ?

• Membrane thickness (h)
• Diffusion coefficient (D)
• Drug partitioning into the membrane (K)
• Permeant surface area

Correct Answer: Drug partitioning into the membrane (K)

Q3. The unstirred water layer (UWL) adjacent to a biological membrane mainly affects which aspect of drug transport?

• Intrinsic membrane diffusion coefficient
• Rate of bulk convective flow across tissue
• Rate-limiting diffusional resistance external to the membrane
• Microbial degradation of drug

Correct Answer: Rate-limiting diffusional resistance external to the membrane

Q4. Which in vitro model is cell-based and expresses many intestinal transporters, making it suitable for assessing both passive and active absorption?

• PAMPA (Parallel Artificial Membrane Permeability Assay)
• Franz diffusion cell with synthetic membrane
• Caco-2 monolayer model
• Shake-flask partitioning test

Correct Answer: Caco-2 monolayer model

Q5. The Noyes-Whitney equation is primarily applied to describe which process relevant to biopharmaceutics?

• Transcellular passive diffusion across epithelium
• Drug dissolution rate from a solid dosage form
• Carrier-mediated transport saturation
• Enzymatic metabolism kinetics

Correct Answer: Drug dissolution rate from a solid dosage form

Q6. In PAMPA, what does the assay model most directly simulate?

• Active transport via P-glycoprotein
• Paracellular transport through tight junctions
• Passive transcellular permeability across lipid membranes
• Metabolic stability in hepatocytes

Correct Answer: Passive transcellular permeability across lipid membranes

Q7. Which parameter describes the steady-state amount of drug crossing a unit area of membrane per unit time per unit concentration difference?

• Permeability coefficient (P)
• Partition coefficient (K)
• Diffusion coefficient (D)
• Flux density (J) without normalization

Correct Answer: Permeability coefficient (P)

Q8. For a weak acid, which condition generally favors its passive absorption across the intestinal epithelium?

• High pH where the acid is ionized
• Low pH where the acid is unionized
• Presence of efflux transporter inhibitors
• High luminal bile salt concentration only

Correct Answer: Low pH where the acid is unionized

Q9. The Higuchi model is commonly used to describe release from matrix dosage forms. It assumes which primary transport mechanism?

• Zero-order convective release
• Saturation-limited carrier transport
• Diffusion-controlled release from a homogeneous matrix
• Enzymatic cleavage governed release

Correct Answer: Diffusion-controlled release from a homogeneous matrix

Q10. Which experimental measure is directly obtained from initial linear portion of cumulative amount versus time plot in a permeability study?

• Apparent permeability coefficient (Papp) only
• Steady-state flux (Jss)
• Diffusion coefficient in the membrane (D) only
• Partition coefficient (K) only

Correct Answer: Steady-state flux (Jss)

Q11. In the context of transporter kinetics, which model is used to describe saturable carrier-mediated uptake?

• Fick’s second law
• Michaelis-Menten kinetics
• Higuchi model
• Henderson-Hasselbalch equation

Correct Answer: Michaelis-Menten kinetics

Q12. The Biopharmaceutics Classification System (BCS) links solubility and permeability. A BCS class I drug is characterized by:

• Low solubility, low permeability
• High solubility, high permeability
• High solubility, low permeability
• Low solubility, high permeability

Correct Answer: High solubility, high permeability

Q13. Which factor would decrease the apparent permeability of a lipophilic drug across an epithelial monolayer?

• Increasing membrane fluidity with short-chain alcohols
• Formation of a drug-protein complex that reduces free drug concentration
• Raising concentration to saturate a binding site in the membrane
• Addition of a permeation enhancer

Correct Answer: Formation of a drug-protein complex that reduces free drug concentration

Q14. When applying Fick’s second law to predict time-dependent concentration profiles, what main feature is accounted for that Fick’s first law does not?

• Spatial concentration gradient at steady state
• Temporal change of concentration (non-steady-state diffusion)
• Partitioning into the membrane
• Effect of pH on ionization

Correct Answer: Temporal change of concentration (non-steady-state diffusion)

Q15. Which statement best describes paracellular transport in epithelia?

• It occurs through the lipid bilayer of cells and is highly lipophilic-dependent
• It is mediated by specific carrier proteins and is saturable
• It occurs through tight junctions and is typically limited to small hydrophilic solutes
• It requires active ATP-dependent pumps to move drug molecules

Correct Answer: It occurs through tight junctions and is typically limited to small hydrophilic solutes

Q16. In permeability experiments, maintaining sink conditions is important because:

• It prevents drug degradation in the donor compartment
• It ensures concentration gradient remains approximately constant for accurate flux measurement
• It increases unstirred water layer thickness to simulate in vivo conditions
• It selectively measures carrier-mediated transport only

Correct Answer: It ensures concentration gradient remains approximately constant for accurate flux measurement

Q17. The apparent permeability coefficient (Papp) in Caco-2 assays is typically calculated using which relationship?

• Papp = (dQ/dt) / (A * C0), where dQ/dt is steady-state rate, A is area, C0 donor concentration
• Papp = Kd * Vd / t, where Kd is dissociation constant
• Papp = (Cdonor – Creceptor) / membrane thickness
• Papp = log P + pKa

Correct Answer: Papp = (dQ/dt) / (A * C0), where dQ/dt is steady-state rate, A is area, C0 donor concentration

Q18. Which experimental technique allows measurement of transepithelial electrical resistance (TEER) to assess monolayer integrity?

• HPLC analysis of transported drug
• Electrochemical impedance measurement across cell layer
• UV-Vis spectrophotometry of donor solution
• PAMPA lipid membrane staining

Correct Answer: Electrochemical impedance measurement across cell layer

Q19. In two-compartment absorption models, the absorption rate constant (ka) primarily governs which process?

• Elimination of drug from the central compartment
• Transfer from central to peripheral compartment
• Rate of drug transfer from the absorption site into systemic circulation
• Metabolic clearance in the liver only

Correct Answer: Rate of drug transfer from the absorption site into systemic circulation

Q20. Which approach can be used to experimentally distinguish between passive diffusion and carrier-mediated uptake?

• Observe linearity of uptake with concentration and test for saturation at higher concentrations
• Measure pH of the donor solution only
• Use only lipophilic drugs in the assay
• Measure only final equilibrium concentration without time course

Correct Answer: Observe linearity of uptake with concentration and test for saturation at higher concentrations

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