Drugs are small molecules that often occur in either a neutral or a charged form, depending on pH. For example, aspirin can be either neutral or lose a proton to be negatively charged. When aspirin is charged, it does not diffuse well into the body. pH varies in the gastrointestinal track. Since the stomach has a low pH (pH=3), it has a larger concentration of neutral aspirin (10-3 M), while the small intestine (pH=6) has a smaller neutral aspirin concentration (10-6 M). For the following, assume that the neutrally charged aspirin molecule has a diffusion coefficient through the cell of 1 x 10-6 cm2/s. A. If a cell is 20 microns in diameter, how long does it take neutrally charged aspirin to diffuseto the center of the cell where the prostaglandins that cause pain are made?B. Let's compare aspirin's uptake in the stomach vs small intestine. Assume the cells lining thestomach and small intestine are the same (same membrane thickness, same diameter, samediffusion coefficient). Also assume the concentration of aspirin is O inside these cells (so wecan calculate the maximum diffusive flux). Based on this, what is the ratio of the maximumdiffusive flux of aspirin into cells lining the stomach versus cells lining the small intestine?C. We'd like to figure out where in the body aspirin is absorbed as determined by its diffusionrate. If the small intestine has a surface area 50 times that of the stomach, what is the ratioof the diffusion rates in the stomach compared to the small intestine?D. In which part of the GI tract is most of the aspirin absorbed?

Since pH affects the solubility of the molecule, which determines the stability of pharmaceuticals,…

Answered: Drugs are small molecules that often…

Human Anatomy & Physiology (11th Edition)

11th Edition

ISBN:9780134580999

Author:Elaine N. Marieb, Katja N. Hoehn

Publisher:Elaine N. Marieb, Katja N. Hoehn

Chapter1: The Human Body: An Orientation

Section: Chapter Questions

Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...

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Drugs are small molecules that often occur in either a neutral or a charged form, depending on pH. For example, aspirin can be either neutral or lose a proton to be negatively charged. When aspirin is charged, it does not diffuse well into the body. pH varies in the gastrointestinal track. Since the stomach has a low pH (pH=3), it has a larger concentration of neutral aspirin (10-3 M), while the small intestine (pH=6) has a smaller neutral aspirin concentration (10-6 M). For the following, assume that the neutrally charged aspirin molecule has a diffusion coefficient through the cell of 1 x 10-6 cm2/s.

A. If a cell is 20 microns in diameter, how long does it take neutrally charged aspirin to diffuse
to the center of the cell where the prostaglandins that cause pain are made?
B. Let's compare aspirin's uptake in the stomach vs small intestine. Assume the cells lining the
stomach and small intestine are the same (same membrane thickness, same diameter, same
diffusion coefficient). Also assume the concentration of aspirin is O inside these cells (so we
can calculate the maximum diffusive flux). Based on this, what is the ratio of the maximum
diffusive flux of aspirin into cells lining the stomach versus cells lining the small intestine?
C. We'd like to figure out where in the body aspirin is absorbed as determined by its diffusion
rate. If the small intestine has a surface area 50 times that of the stomach, what is the ratio
of the diffusion rates in the stomach compared to the small intestine?
D. In which part of the GI tract is most of the aspirin absorbed?

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