Maharashtra State Board · Class 12 · Chemistry · Chapter 14

Biomolecules — Formula Sheet

Board Formulas

10 formulas

1.Peptide Bond★
$α -amino acid H_{2} N - C H R - C O O H + H_{2} N - C H R^{'} - C O O H \to H_{2} N - C H R - C O - N H - C H R^{'} - C O O H + H_{2} O$
Amide bond formed by condensation between −COOH and −NH₂ of two amino acids.
2.Zwitterion Form of Amino Acid
$H_{3} N + - C H R - C O O^{-}$
At isoelectric pH, amino acid exists as dipolar zwitterion. Explains high melting point and water solubility.
3.Isoelectric Point (pI)
$p I = \frac{1}{2} (p K_{a 1} + p K_{a 2})$
pH at which amino acid carries no net charge. Precipitates most easily here.
4.Glycosidic Bond★
$Two sugars + glycosidic bond \to disaccharide + H_{2} O$
Formed between anomeric −OH of one sugar and −OH of another. Basis of polysaccharides.
5.Fischer to Haworth Conversion — Cyclisation
$aldose or ketose ⇌ cyclic hemiacetal/hemiketal$
Glucose forms pyranose (6-membered), fructose forms furanose (5-membered). Anomeric C carries new −OH.
6.Base Pairing in DNA★
$A = T (2 H-bonds), G \equiv C (3 H-bonds)$
Chargaff's rule: %A = %T and %G = %C in any DNA.
7.DNA vs RNA — Sugar
$DNA: 2-deoxyribose; RNA: ribose$
DNA lacks 2′-OH; RNA has 2′-OH. Base uracil replaces thymine in RNA.
8.Enzyme Rate — Michaelis-Menten (simplified)
$v = \frac{V _{ma x} [ S ]}{K _{m} + [ S ]}$
Enzyme reaction rate. K_m = substrate concentration at half V_max. Not always in Maharashtra syllabus but appears in HOTS.
9.Optical Activity of Glucose★
$[α]_{D}^{25 ° C} = + 52.7° (equilibrium)$
Mutarotation: α-glucose (+112°) and β-glucose (+18.7°) equilibrate to give +52.7°.
10.Iodine Test for Starch
$Starch + I_{2} \to Deep blue colour$
Amylose forms complex with iodine giving characteristic blue colour. Cellulose does not.