Vitamins & Minerals MCQs

Biochemistry · 5 free questions with answers & explanations.

1. A 30-year-old chronic alcoholic is brought to the emergency department with confusion, ophthalmoplegia, and ataxia. Intravenous dextrose is started, and his condition acutely worsens. Deficiency of which vitamin is responsible, and why does glucose administration precipitate deterioration?
2. A 4-year-old child from a low-income household presents with bowed legs, widening of the wrists, and a rachitic rosary on chest examination. Serum calcium is low, phosphate is low, and parathyroid hormone (PTH) is elevated. 25-hydroxyvitamin D is severely deficient. In which organ does the hydroxylation of 25-OH-D3 to the biologically active 1,25-(OH)2-D3 (calcitriol) primarily occur?
3. Vitamin K is essential for the post-translational modification of clotting factors II, VII, IX, and X. The gamma-carboxylation of glutamic acid residues requires vitamin K. Warfarin inhibits VKORC1, blocking the recycling of vitamin K epoxide back to its active (reduced) form. Which of the following is the direct biochemical consequence of warfarin therapy?
4. A 6-month-old exclusively breastfed infant presents with pallor, a smooth red tongue, and hypersegmented neutrophils on peripheral smear. Serum B12 is normal, but red cell folate is low. The mother has been on methotrexate for rheumatoid arthritis. Methotrexate causes megaloblastic anemia by which mechanism?
5. A 55-year-old male patient with carcinoid syndrome undergoes workup. Carcinoid tumors divert tryptophan toward serotonin synthesis, leaving little tryptophan for niacin synthesis. The patient develops a dermatitis that worsens on sun-exposed areas, diarrhea, and dementia. Which vitamin's deficiency is classically described by the mnemonic '4 Ds'?