Question

Hartnup disease patients are able to get some of the benefit of the protein they consume because A. only the neutral amino acid carrier is defective. B. di-and tripeptides from protein digestion are absorbed by a different carrier (PepT1). C. their endo-and exopeptidases are normal. D. all of the above. E. none of the above.

Short answer

Answer: D. All of the above.

Step-by-step solution

A. Only the neutral amino acid carrier is defective

Hartnup disease is a disorder that affects the absorption of certain amino acids, specifically neutral amino acids. The cause is a malfunction in the specific carrier responsible for their absorption. This option could be one of the reasons why patients still get some benefit from protein consumption.

B. Di-and tripeptides from protein digestion are absorbed by a different carrier (PepT1)

Protein digestion involves breaking down proteins into smaller amino acid units, including di- and tripeptides. These smaller units are absorbed by other carriers in the intestine, such as PepT1. Since Hartnup disease only affects the carrier for neutral amino acids, patients can still absorb some peptides through a different carrier like PepT1. This option also contributes to the patients receiving some benefits from the proteins they consume.

C. Their endo- and exopeptidases are normal

Endo- and exopeptidases are enzymes that help break down proteins into smaller peptides and amino acids. In Hartnup disease, these enzymes are not affected and function normally. Therefore, the digestion of proteins still takes place, and some peptides may be absorbed. This option also plays a role in patients receiving some benefits from protein consumption.

D. All of the above

All the mentioned factors in options (A), (B), and (C) together contribute to Hartnup disease patients' ability to receive some benefits from protein consumption. They all explain different aspects of absorption and digestion, which play a role in the overall benefit of protein for these patients.

E. None of the above

Since options (A), (B), and (C) explain various aspects of how patients with Hartnup disease still get some benefits from protein, this option is incorrect. After analyzing all options, the correct answer is: D. All of the above.