KROK 1 2020 – Question 58 · KROK (Medicine) · Biological Chemistry

One of the causes of pernicious anemia is the disturbed synthesis of transcorrin - Castle’s intrinsic factor - in the parietal cells of the stomach. What substance is called Castle’s extrinsic factor?

  1. A. Pyridoxine
  2. B. Riboflavin
  3. C. Cobalamin
  4. D. Biotin
  5. E. Folic acid
Hint

In the two-part Castle system one component comes with food and the other is made by gastric parietal cells, so ask which nutrient needs a stomach-derived carrier.

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