One-Page NEET Cheat Sheet for OC-09
Carbohydrates — Core Facts:
- Glucose: , aldohexose; SMILES:
OC[C@@H](O)[C@H](O)[C@@H](O)[C@@H](O)C=O - Fructose: , ketohexose (isomer of glucose); both reducing sugars
- Alpha-glucose: C1-OH down (Haworth); Beta-glucose: C1-OH up; interconvert by mutarotation
- Sucrose (alpha-1,2 bond, non-reducing) | Lactose (beta-1,4, reducing) | Maltose (alpha-1,4, reducing)
- Starch: amylose (alpha-1,4, linear) + amylopectin (alpha-1,4 + alpha-1,6, branched every 24-30)
- Glycogen: like amylopectin but branched every 8-12 units (more branched)
- Cellulose: beta-1,4 (indigestible by humans; no cellulase)
Proteins — Core Facts:
- General amino acid: -CHR-COOH; glycine (R=H) = only achiral amino acid
- Peptide bond: -CO-NH- (condensation; n-1 bonds for n amino acids; NOT broken by denaturation)
- Peptide bond: planar, partial double-bond character (~40%), restricted rotation
- 1° structure: AA sequence (peptide bonds); 2° structure: alpha-helix/beta-sheet (H-bonds)
- 3° structure: 3D fold (disulfide + hydrophobic + ionic + H-bonds); 4° structure: subunits
- Haemoglobin: 4 subunits (2α+2β); myoglobin: single chain
- Denaturation: breaks 2°/3°/4° but NOT 1° (peptide bonds intact)
Vitamins — Core Facts:
- Fat-soluble: A (retinol, night blindness), D (calciferol, rickets), E (tocopherol, infertility), K (phylloquinone, clotting delay)
- B1/thiamine → beriberi | B2/riboflavin → cheilosis | B3/niacin → pellagra (4Ds)
- B6/pyridoxine → convulsions | B9/folic acid → megaloblastic anaemia + NTDs
- B12/cyanocobalamin → pernicious anaemia (contains Co, needs intrinsic factor)
- C/ascorbic acid → scurvy (prolyl hydroxylase cofactor → collagen)
Nucleic Acids — Core Facts:
- DNA: deoxyribose + A,T,G,C; double helix; A-T (2 H-bonds); G-C (3 H-bonds)
- RNA: ribose + A,U,G,C; mostly single-stranded; U replaces T
- Chargaff: [A]=[T], [G]=[C] in dsDNA
- Higher G-C% → higher Tm (melting temperature)
- mRNA = genetic code carrier | tRNA = cloverleaf, anticodon, 3'-CCA | rRNA = ribosome structure
- Central dogma: DNA → RNA → Protein
Counting rules:
- Peptide bonds = n-1 (n = amino acids)
- Total H-bonds in DNA = (A-T pairs × 2) + (G-C pairs × 3)
- Chargaff: if [A]=x%, then [T]=x%, [G]=[C]=(100-2x)/2%