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Block 3 — Biochemistry MCQs
SZABMU · 425 MCQs with clinical pearls · Prof Jariya
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Sections in this szabmu
- Fatty Acid Structure and Classification — 43 MCQs
- Cholesterol Synthesis and Regulation — 27 MCQs
- Vitamin A — 23 MCQs
- Vitamin D — 21 MCQs
- Eicosanoids — 21 MCQs
- Cofactors and Coenzymes — 16 MCQs
- Vitamin K — 14 MCQs
- Enzyme Inhibition Clinical — 14 MCQs
- Thiamine — B1 — 13 MCQs
- Nutritional Significance of Lipids — 13 MCQs
- Lipoproteins and Lipoprotein Disorders — 13 MCQs
- Niacin — B3 — 11 MCQs
- Phospholipids — 11 MCQs
- Essential Fatty Acids — 10 MCQs
Sample MCQs with clinical pearls
A 6-year-old boy living in an orphanage presents with difficulty seeing at night. He has been surviving on a monotonous diet of rice and bread for the past year with no animal products. Eye examination is normal in daylight. Which vitamin deficiency is most likely responsible?
A) Vitamin A ✔
B) Vitamin B12
C) Vitamin C
D) Vitamin D
E) Vitamin E
NIGHT BLINDNESS - nyctalopia - is the EARLIEST sign of vitamin A deficiency, because 11-cis-RETINAL is the chromophore of RHODOPSIN in the rods, which mediate vision in dim light. The rods are affected before the cones. It is fully reversible with vitamin A if treated before structural eye damage occurs. Vitamin A deficiency remains a leading cause of preventable childhood blindness. MEMORY: 'The rods fail first, so the dark goes first.'
A 5-year-old boy presents to a community eye camp. He has whitish, foamy, triangular patches on the temporal side of his conjunctiva. His parents report that he often struggles to see in dim light. These whitish foamy patches represent which stage of vitamin A deficiency?
A) Bitot's spots ✔
B) Conjunctival xerosis
C) Corneal xerosis
D) Keratomalacia
E) Nyctalopia
BITOT SPOTS are foamy, triangular, greyish-white plaques on the bulbar conjunctiva, made of keratinised epithelium and gas-forming bacteria. They indicate established vitamin A deficiency, one stage beyond night blindness. Vitamin A maintains epithelial differentiation; its loss causes SQUAMOUS METAPLASIA and keratinisation of mucosal surfaces throughout the body, not only in the eye. MEMORY: 'Foamy triangles on the white of the eye mean vitamin A is gone.'
A malnourished 4-year-old child presents with severe eye discomfort. Examination shows loss of corneal lustre and dryness extending over the corneal surface. This ocular finding represents which stage of vitamin A deficiency?
A) Bitot's spots
B) Conjunctival xerosis
C) Corneal xerosis ✔
D) Keratomalacia
E) Nyctalopia
CORNEAL XEROSIS is drying and hazing of the cornea itself, a more advanced stage than conjunctival xerosis or Bitot spots. The xerophthalmia sequence runs: night blindness, conjunctival xerosis, Bitot spots, corneal xerosis, then KERATOMALACIA with corneal ulceration and melting. Up to corneal xerosis the changes are reversible; beyond it, scarring and blindness follow. This is a medical emergency needing immediate high-dose vitamin A. MEMORY: 'Once the cornea clouds, sight is on a deadline.'
425 MCQs are arranged to the learning outcomes of this szabmu.
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