Q60 - pH-Dependent Membrane Diffusion of Aspirin and Arginine
Polarity, charge and molecular weight of molecules can affect their rate of passive diffusion through membranes. Amino acids and drugs like aspirin differ in both efficiency and location of absorption. In the figure below the chemical structure the pKa values of aspirin and arginine are represented.
Figure Q.60
Figure 1.
Using the information and data, determine which of the statements are true or which are false.
A. Aspirin diffuses through membranes mainly in the stomach because more aspirin molecules are in deprotonated form at pH of about 1.6 in the stomach.
B. Based on molecular weight, one would expect Aspirin to diffuse more easily through membrane than Arginine
C. Optimal pH range for Arginine absorption by passive diffusion is between 2.18 and 9.04.
D. Omeprazole, a proton pump inhibitor, blocks the entry of Aspirin into the blood in the initial few minutes after oral administration.
Question reproduced from IBO 2016, Theoretical Paper B, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)