Biochemistry Cheat Sheet 2026

The 30 highest-yield Biochemistry facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Lesch-Nyhan syndrome results from a deficiency of which enzyme in purine metabolism? → Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)
2. The enzyme lactase cleaves lactose into which two monosaccharides? → Glucose + galactose
3. Hemoglobin is an example of a protein with which level of structural organization? → Quaternary
4. The net ATP yield from complete oxidation of one molecule of glucose through glycolysis and oxidative phosphorylation is approximately: → 30-32 ATP
5. Alpha-helices and beta-pleated sheets are examples of which level of protein structure? → Secondary
6. Glycogen is the storage polysaccharide in animals. Its branching involves which type of linkage? → Alpha(1→4) in chains with alpha(1→6) at branch points
7. Mass spectrometry in proteomics identifies proteins by measuring: → The mass-to-charge ratio (m/z) of peptide fragments
8. Vitamin C (ascorbate) is required for collagen synthesis because it is needed for: → Hydroxylation of proline and lysine residues
9. Pellagra, characterized by the 4 D's (Dermatitis, Diarrhea, Dementia, Death), is caused by deficiency of: → Niacin (B3)
10. Vitamin D3 (cholecalciferol) is hydroxylated first in the liver to 25-hydroxyvitamin D, then in the kidney to its active form: → 1,25-dihydroxyvitamin D (calcitriol)
11. Familial hypercholesterolemia is caused by a defect in: → LDL receptor function
12. In a Western blot, after SDS-PAGE and transfer to membrane, what is the purpose of the primary antibody? → To specifically recognize the target protein
13. Gluconeogenesis is the synthesis of glucose from non-carbohydrate precursors. Which of the following is NOT a gluconeogenic precursor? → Acetyl-CoA
14. Which of the following statements about the Cori cycle is TRUE? → Lactate produced in the muscles is converted back to glucose in the liver.
15. The fluid mosaic model of the cell membrane was proposed by: → Singer and Nicolson
16. CRISPR-Cas9 gene editing creates targeted double-strand DNA breaks using which component to guide it to the correct genomic location? → A single guide RNA (sgRNA) complementary to the target sequence
17. 5-Fluorouracil (5-FU) exerts its anticancer activity primarily by inhibiting which enzyme? → Thymidylate synthase
18. Which nucleotide intermediate serves as the branch point from which both AMP and GMP are synthesized in the purine de novo pathway? → IMP (inosine monophosphate)
19. Which type of fatty acid contains one double bond? → Monounsaturated fatty acid
20. Competitive inhibition of an enzyme: → Increases apparent Km without changing Vmax
21. Which of the following is a key regulatory enzyme in the citric acid cycle? → Isocitrate dehydrogenase
22. Which disaccharide is composed of glucose and fructose joined by an alpha(1→2) glycosidic bond? → Sucrose
23. PRPP amidotransferase, which catalyzes the first committed step of de novo purine synthesis, is allosterically inhibited by which molecules? → AMP, ADP, ATP, GMP, GDP, and GTP
24. Fatty acid synthesis occurs in which cellular compartment? → Cytosol
25. Vitamin K is required for the gamma-carboxylation of which proteins critical for blood clotting? → Clotting factors II, VII, IX, and X
26. The saponification number (saponification value) of a fat is a measure of: → The average molecular weight of fatty acids
27. Riboflavin (Vitamin B2) is the precursor for which two coenzymes? → FAD and FMN
28. Which of the following best describes the function of tRNA in translation? → Carries amino acids to the ribosome and matches them to the mRNA codon.
29. Collagen's unique triple-helix structure is stabilized primarily by which amino acid's repeated occurrence? → Both B and C
30. Ketone bodies are produced in the liver primarily from excess: → Acetyl-CoA