Which substances are absorbed in the stomach?

Which substances are absorbed in the stomach?

• A. Weak acids and alcohol
• B. Lipophilic drugs
• C. Water
• D. Proteins

Answer: (A)

In the acidic environment of the stomach, absorption favors small, non-ionized molecules that can diffuse through the gastric mucosa. Weak acids become protonated at low pH, existing largely in the non-ionized form, which allows them to cross cell membranes readily and be absorbed there. Ethanol is a small, lipophilic molecule and also diffuses across the gastric lining efficiently, so it is absorbed in the stomach as well. Water is absorbed mostly later in the GI tract (primarily the small intestine), proteins are not absorbed intact in the stomach (they’re digested first), so the combination of weak acids and alcohol best represents what is absorbed in the stomach.

In the acidic environment of the stomach, absorption favors small, non-ionized molecules that can diffuse through the gastric mucosa. Weak acids become protonated at low pH, existing largely in the non-ionized form, which allows them to cross cell membranes readily and be absorbed there. Ethanol is a small, lipophilic molecule and also diffuses across the gastric lining efficiently, so it is absorbed in the stomach as well. Water is absorbed mostly later in the GI tract (primarily the small intestine), proteins are not absorbed intact in the stomach (they’re digested first), so the combination of weak acids and alcohol best represents what is absorbed in the stomach.