CBSE · Class 12 · Chemistry · Chapter 10

Biomolecules — Formula Sheet

Board Formulas

9 formulas

1.Molecular Formula of Glucose
$C_{6} H_{12} O_{6}, M = 180 g/mol; aldohexose$
Open-chain form has 5 –OH groups and one –CHO. Cyclic (pyranose) form is 6-membered ring — α and β anomers differ at C-1.
2.Sucrose Hydrolysis (Inversion of Sugar)★
$C_{12} H_{22} O_{11} + H_{2} O H^{+} / invertase glucose + fructose$
Sucrose is dextrorotatory but the product mixture is levorotatory (fructose has larger −ve rotation) — hence 'invert sugar'.
3.Reducing vs Non-reducing Sugars★
$Reducing: glucose, fructose, maltose, lactose; Non-reducing: sucrose$
Reducing sugars have a FREE hemiacetal/hemiketal (open-chain aldehyde/ketone available). Detected by Tollens', Fehling's, Benedict's test.
4.Peptide Bond Formation★
$R_{1} -COOH + H_{2} N-R_{2} - H_{2} O R_{1} -CO-NH-R_{2}$
Condensation of –COOH of one amino acid with –NH₂ of next. The C–N amide bond is planar and partially double-bond (resonance).
5.Zwitterion (Amino Acid at Isoelectric Point)
$H_{2} N-CHR-COOH ⇌ H_{3} N + -CHR-COO^{-}$
At isoelectric pH the amino acid exists as a dipolar ion. Solid amino acids have high m.p. and are crystalline because of ionic zwitterion form.
6.Chargaff's Rules (Base Pairing in DNA)★
$[A] = [T], [G] = [C], [A] + [G] = [T] + [C] = 50%$
Purines (A, G) pair with pyrimidines (T, C). Two H-bonds in A=T pair, three in G≡C pair.
7.α-Amino Acid General Structure
$H_{2} N-CH(R)-COOH (α -carbon bears -NH_{2}, -COOH, -H, -R)$
20 standard α-amino acids in proteins. Except glycine (R = H), all α-carbons are chiral ⇒ optically active. All natural amino acids are L-series (S-configuration except cysteine).
8.Michaelis-Menten Equation
$v = \frac{v _{m a x} [ S ]}{K _{m} + [ S ]}$
$v$ : Reaction velocity · $v_{m a x}$ : Maximum velocity (at saturating [S]) · $[S]$ : Substrate concentration · $K_{m}$ : Michaelis constant
Basic enzyme kinetics. Km = [S] at which v = v_max/2; small Km ⇒ high affinity.
9.Glycosidic Linkage Classification
$Maltose: α -1,4; Lactose: β -1,4; Sucrose: α -1, β -2; Starch amylose: α -1,4; Cellulose: β -1,4$
α-linkage: digestible by humans (starch, glycogen). β-linkage: indigestible fibre (cellulose).