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Exampromax – Stuvia US 2025/2026
Approved By:
Exampromax – Stuvia US
FIRST AID USMLE STEP 1 – VITAMINS Questions
with Detailed Verified Answers (100% Correct Answers)
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Vitamin A (retinol) – Function
Ans: Antioxidant; constituent of visual pigments (retinal); essential for
normal differentiation of epithelial cells into specialized tissue (pancreatic
cells, mucus-secreting cells); prevents squamous metaplasia. Used to treat
measles and acute promyelocytic leukemia (APL).
Vitamin A (retinol) – Deficiency
Ans: Night blindness (nyctalopia); dry, scaly skin (xerosis cutis); corneal
degeneration (keratomalacia); Bitot spots on conjunctiva;
immunosuppression.
Vitamin A (retinol) – Excess
Ans: Acute toxicity—nausea, vomiting, vertigo, and blurred vision.
Chronic toxicity—alopecia, dry skin (eg, scaliness), hepatic toxicity and
enlargement, arthralgias, and pseudotumor cerebri. Teratogenic (cleft
palate, cardiac abnormalities), therefore a ⊝ pregnancy test and two forms
of contraception are required before isotretinoin (vitamin A derivative) is
prescribed.
Vitamin A (retinol) – Extra
Ans: Retinol is vitamin A, so think retin-A (used topically for wrinkles and
Acne). Found in liver and leafy vegetables. Use oral isotretinoin to treat
severe cystic acne. Use all-trans retinoic acid to treat acute promyelocytic
leukemia. Isotretinoin is teratogenic.
Vitamin B1 (thiamine) – Function
Ans: In thiamine pyrophosphate (TPP), a cofactor for several
dehydrogenase enzyme reactions: +Pyruvate dehydrogenase (links
glycolysis to TCA cycle) +α-ketoglutarate dehydrogenase (TCA cycle)
+Transketolase (HMP shunt) +Branched-chain ketoacid dehydrogenase
Vitamin B1 (thiamine) – Deficiency
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Exampromax – Stuvia US 2025/2026
Approved By:
Exampromax – Stuvia US
Ans: Impaired glucose breakdown p ATP depletion worsened by glucose
infusion; highly aerobic tissues (eg, brain, heart) are affected first. In
alcoholic or malnourished patients, give thiamine before dextrose to reduce
risk of precipitating Wernicke encephalopathy. Diagnosis made by increase
in RBC transketolase activity following vitamin B1 administration.
Vitamin B1 (thiamine) – Extra
Ans: Think ATP: α-ketoglutarate dehydrogenase, Transketolase, and
Pyruvate dehydrogenase. Spell beriberi as Ber1Ber1 to remember vitamin
B1. Wernicke-Korsakoff syndrome —confusion, ophthalmoplegia, ataxia
(classic triad) + confabulation, personality change, memory loss
(permanent). Damage to medial dorsal nucleus of thalamus, mammillary
bodies. Dry beriberi —polyneuritis, symmetrical muscle wasting. Wet
beriberi —high-output cardiac failure (dilated cardiomyopathy), edema.
Vitamin B2 (riboflavin) – Function
Ans: Component of flavins FAD and FMN, used as cofactors in redox
reactions, eg, the succinate dehydrogenase reaction in the TCA cycle.
Vitamin B2 (riboflavin) – Deficiency
Ans: Cheilosis (inflammation of lips, scaling and fissures at the corners of
the mouth), Corneal vascularization.
Vitamin B2 (riboflavin) – Extra
Ans: FAD and FMN are derived from riboFlavin (B2 ≈ 2 ATP). The 2 C’s
of B2 .
Vitamin B3 (niacin) – Function
Ans: Constituent of NAD+, NADP+ (used in redox reactions). Derived
from tryptophan. Synthesis requires vitamins B2 and B6 . Used to treat
dyslipidemia; lowers levels of VLDL and raises levels of HDL.
Vitamin B3 (niacin) – Deficiency
