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MDCAT Prep · Biology · Quick Reference
Lesson 3 — Biological Molecules Cheat Sheet
In one line: Carbs, proteins, lipids and nucleic acids each have a signature test — pair the molecule with its test and its monomer, not just in isolation.
Key Ideas
1Carbohydrates. Mono (glucose, fructose, galactose), Di (sucrose, lactose, maltose), Poly (starch, glycogen, cellulose).
2Proteins. 20 amino acid monomers. 1° = sequence, 2° = α-helix/β-sheet (H-bonds), 3° = 3D shape.
3Lipids. Triglyceride = glycerol + 3 fatty acids. Saturated = solid, unsaturated (double bonds) = liquid.
4DNA vs RNA. DNA: double-strand, deoxyribose, A-T-C-G, nucleus. RNA: single-strand, ribose, A-U-C-G, nucleus+cytoplasm.
5Exam pairing. MDCAT loves pairing a test with its result — memorise them as pairs.
Biochemical Tests
Benedict's test
Reducing sugars → brick-red
Iodine test
Starch → blue-black
Biuret test
Proteins → purple
Emulsion test
Lipids → white/cloudy
DNA = deoxyribose + A-T-C-G, double strand
RNA = ribose + A-U-C-G, single strand