Metabolism USMLE Step 1 Practice Question
A 4 year old boy recently immigrated from a resource limited region is brought to clinic for difficulty seeing at night. His mother says he frequently bumps into furniture when the lights are dim. Examination shows dry conjunctivae with foamy patches on the sclera. Deficiency of which of the following molecules is most likely responsible?
Answer choices
- APhylloquinone, a clotting factor cofactor
- BThiamine pyrophosphate, a dehydrogenase cofactor
- CTocopherol, a membrane antioxidant
- DCalcitriol, a steroid hormone
- ERetinal, a component of rhodopsinCorrect answer
- FRetinol, the storage form of vitamin A in the liver
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