Biochemistry
Lessons
Illustrated, high-yield walkthroughs of the biochemistry concepts the boards test most.
A board-focused sweep of the 13 essential vitamins — their coenzyme roles, classic deficiency syndromes, and toxicities — organized around the fat-soluble (ADEK) vs water-soluble split and the high-yield B12-vs-folate and thiamine pitfalls Step 1 loves to test.
The board-tested glycogen storage diseases (Von Gierke, Pompe, Cori, McArdle) and lysosomal storage diseases (sphingolipidoses and mucopolysaccharidoses), organized by the deficient enzyme, the substrate that accumulates, and the vignette buzzwords that separate the look-alikes.
A high-yield Step 1 review of glycolysis and gluconeogenesis: rate-limiting enzymes, the four irreversible bypass reactions, reciprocal control by fructose-2,6-bisphosphate/insulin/glucagon, and the classic tested diseases (pyruvate kinase deficiency, Von Gierke).
A board-focused walkthrough of the TCA cycle and oxidative phosphorylation, anchored on rate-limiting enzymes, shared cofactors, and the exact site plus clinical picture of each ETC poison and uncoupler (cyanide, CO, oligomycin, DNP, salicylates).
A Step 1–focused walkthrough of amino acid nitrogen handling and the urea cycle: enzyme sequence and compartments, CPS1/NAG regulation, orotic-acid localization of the block, and the hyperammonemia cascade — anchored by the OTC-deficiency neonate and hepatic-encephalopathy adult vignettes, the OTC vs. hereditary orotic aciduria distinction, and next-best-step management.
A board-focused walkthrough of fatty acid oxidation and synthesis: the carnitine shuttle, reciprocal malonyl-CoA/CPT-I regulation, and the FAO disorders (MCAD, primary carnitine deficiency, CPT-II) that present as hypoketotic hypoglycemia, plus why the liver makes but cannot use ketone bodies.
A board-focused walkthrough of purine and pyrimidine metabolism — de novo synthesis, salvage, and catabolism — tied to the two ways STEP 1 tests it: chemotherapy/immunosuppressant drug targets and inherited enzyme deficiencies (Lesch-Nyhan, ADA-SCID, hereditary orotic aciduria). Emphasizes next-best-step discriminators such as orotic aciduria vs. OTC deficiency.
A board-focused walk through the DNA replication fork (its enzymes and the drugs that block them) and the five DNA repair pathways, each paired with its classic inherited cancer-prone syndrome and next-best-step management.
Sample questions
Stems only. Sign up free to see answer choices, correct option, and the rationale.
A newborn with ambiguous genitalia and a 46,XY karyotype develops vomiting, low serum sodium concentration, and high serum potassium. Which of the following proteins is most likely to be abnormal?
A child has ambiguous genitalia including an apparent small phallus and scrotum. The child’s DNA hybridizes to probes from the sex-determining region of the Y (SRY). Based on the clinical findings and dot-blot analysis, which of the following terms applies?
The dot-blot shown below examines DNA from a child with ambiguous genitalia after polymerase chain reaction (PCR) amplification and hybridization with DNA probes from the X and Y chromosome. In this case, the Y chromosome probe is from the SRY region of Yp that has recently been characterized as the male-determining region. DNA from control male and female patients is also applied to the dot-blot. Based on the dot-blot results, which is the most likely conclusion?
Sample flashcards
Which one of the following steps results in the formation of a phospholipid? You picked: A. Step A
Cell cycle checkpoints?
Cytochrome P450 induction?
Cytochrome P450 inhibition?
Vitamin K function?
Translation overview?
FAQ
What's covered in the Biochemistry topic?
Biochemistry covers high-yield mechanisms, clinical presentations, diagnostic workup, and management — drawn from First Aid, Pathoma, and the NBME content outline.
How many practice questions does Biochemistry have?
489 board-style multiple-choice questions and 103 spaced-repetition flashcards. Sign up free to drill them with adaptive difficulty and a Socratic AI tutor that explains every wrong answer.
Is Biochemistry on USMLE Step 1 or Step 2 CK?
Biochemistry appears on both Step 1 (foundational mechanisms) and Step 2 CK (clinical decision-making). Our questions are tagged by exam target so you can filter to just the Step you're studying.
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