BH4 deficiency hyperphenylalaninemia Practice Question
Neuro deterioration DESPITE diet + dihydropteridine reductase
clinical diagnosis vignetteIncluded in free practice
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Question-First Step 1 Biochemistry Practice
USMLE Step 1 Biochemistry Practice Questions
Browse BiochemStep practice-question pages by foundational science domain, topic, and reasoning focus. Each page points back to the free Step 1-style question set so you can move from review to practice quickly.
Amino Acid Metabolism
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BH4 deficiency hyperphenylalaninemia Practice Question
Neuro deterioration DESPITE diet + dihydropteridine reductase
enzyme / mechanismIncluded in free practice
BH4 deficiency hyperphenylalaninemia Practice Question
Neuro deterioration DESPITE diet + dihydropteridine reductase
metabolic consequence / accumulation / deficiencyIncluded in free practice
Classic PKU (phenylalanine hydroxylase deficiency) Practice Question
Musty odor + eczema + fair complexion + developmental delay
clinical diagnosis vignetteIncluded in free practice
Classic PKU (phenylalanine hydroxylase deficiency) Practice Question
Musty odor + eczema + fair complexion + developmental delay
enzyme / mechanismIncluded in free practice
Classic PKU (phenylalanine hydroxylase deficiency) Practice Question
Musty odor + fair complexion + developmental delay
metabolic consequence / accumulation / deficiencyIncluded in free practice
Classic PKU (phenylalanine hydroxylase deficiency) Practice Question
Musty odor + fair complexion + developmental delay
treatment / physiology / regulationIncluded in free practice
CPS I deficiency Practice Question
Neonatal Hyperammonemia + Normal Orotic Acid
clinical diagnosis vignetteIncluded in free practice
CPS I deficiency Practice Question
Normal orotic acid + low BUN + hyperammonemia
enzyme / mechanismIncluded in free practice
CPS I deficiency Practice Question
Neonatal hyperammonemia with respiratory alkalosis and normal urinary orotic acid
metabolic consequence / accumulation / deficiencyIncluded in free practice
Maple syrup urine disease (BCKD complex deficiency) Practice Question
Day-5 neonate with progressive encephalopathy and sweet odor after a normal birth
clinical diagnosis vignetteIncluded in free practice
Maple syrup urine disease (BCKD complex deficiency) Practice Question
Day-5 neonate, progressive encephalopathy, sweet odor after normal birth
enzyme / mechanismIncluded in free practice
Maternal PKU teratogenicity Practice Question
Uncontrolled maternal Phe + fetal microcephaly + cardiac defects
clinical diagnosis vignetteIncluded in free practice
Maternal PKU teratogenicity Practice Question
Maternal Phe
metabolic consequence / accumulation / deficiencyIncluded in free practice
Maternal PKU teratogenicity Practice Question
Pre-conception diet
treatment / physiology / regulationIncluded in free practice
OTC deficiency Practice Question
Male infant + Hyperammonemia + Orotic aciduria
clinical diagnosis vignetteIncluded in free practice
OTC deficiency Practice Question
Neonate + Hyperammonemia + Low BUN + Orotic aciduria
mechanism of orotic acid elevationIncluded in free practice
Homocystinuria
Homocystinuria (cystathionine beta-synthase deficiency) Practice Question
Downward lens subluxation + marfanoid habitus + childhood thrombosis
clinical diagnosis vignetteIncluded in free practice
Homocystinuria (cystathionine beta-synthase deficiency) Practice Question
Downward lens subluxation + marfanoid habitus + thrombosis
enzyme / mechanismIncluded in free practice
Homocystinuria (cystathionine beta-synthase deficiency) Practice Question
Downward lens subluxation + marfanoid habitus + thrombosis
metabolic consequence / accumulation / deficiencyIncluded in free practice