# Biomolecules Notes, Class 12 Chemistry | SwaVid Biomolecules, NCERT Class 12 Chemistry: notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-12/chemistry/chapter/biomolecules Source: https://www.swavid.com/cbse/class-12/chemistry/chapter/biomolecules # Biomolecules ## Formulas and definitions ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 12 Chemistry on SwaVid ### Classification of carbohydrates ### Structure and reactions of glucose ### Disaccharides and polysaccharides ### Amino acids and peptide bond ### Structure and denaturation of proteins ### Nucleic acids ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 12 › Chemistry › Biomolecules Notes written by SwaVid from the NCERT textbook. Class 12 Chemistry, Unit 10. Key ideas, formulas and common mistakes. CBSE prints 7 marks for Unit 10, not for this chapter alone. Short answer. This chapter covers the structure, classification, and biological functions of carbohydrates, proteins, enzymes, vitamins, and nucleic acids. Students learn how complex chemical molecules sustain life processes through specific bonds and functional groupings. Source: NCERT Chemistry Part II (Reprint 2026-27) , Unit 10, Biomolecules Carbohydrates are polyhydroxy aldehydes or ketones, or substances that produce them on hydrolysis. They are divided into monosaccharides, oligosaccharides, and polysaccharides based on the number of sugar units formed during hydrolysis. Glucose is an aldohexose known as dextrose. It exhibits an open-chain structure containing one aldehyde and five hydroxyl groups, as well as cyclic pyranose structures that account for mutarotation and the existence of α- and β-anomers. Monosaccharides link together via glycosidic linkages formed by the loss of a water molecule. Sucrose is a non-reducing disaccharide composed of α-D-glucose and β-D-fructose, whereas starch and cellulose serve as storage and structural polymers respectively. Amino acids contain both amino and carboxyl functional groups. In aqueous solution, they exist as dipolar zwitterions, and they link through peptide bonds (-CO-NH-) to form polypeptides and proteins. Proteins have primary, secondary (α-helix and β-pleated sheet), tertiary, and quaternary levels of structure. Physical or chemical changes disrupt the hydrogen bonding in secondary and tertiary structures, causing denaturation without altering the primary structure. Nucleic acids are polymers of nucleotides, where each nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group. DNA contains adenine, guanine, cytosine, and thymine with 2-deoxyribose, while RNA contains uracil instead of thymine with ribose. Try each question first. Then tap it to see the answer. Identify the reagent: prolonged heating with HI acts as a strong reducing agent. Apply the reaction to the 6-carbon chain of glucose. All carbon atoms are reduced to form a straight chain alkane: n-hexane. n-Hexane Check the general formula of α-amino acids: R-CH(NH₂)-COOH. For glycine, the side chain R is -H, giving the formula H-CH(NH₂)-COOH. The central α-carbon is bonded to two identical hydrogen atoms, making it achiral. Glycine, because its α-carbon is achiral Identify the open-chain aldehyde group: glucose normally shows reactions of aldehydes. Recall the cyclic hemiacetal form: the -CHO group is involved in ring formation with the C5 hydroxyl group. Since only an extremely small fraction of free -CHO exists in dynamic equilibrium, it does not form the hydrogen sulphite addition product. The aldehyde group is locked within the stable cyclic hemiacetal ring structure. Aldehydes, Ketones and Carboxylic Acids . Amines . The 10 chapters of Class 12 Chemistry . CBSE does not give marks to one chapter. It prints 7 marks for Unit 10, Biomolecules, which includes Biomolecules. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. This is the last chapter in the NCERT books for Class 12 Chemistry. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Unit 10 NCERT book - 7 marks, Unit 10 - 3 quick checks - Calling sucrose a reducing sugar . Check the functional groups involved in the glycosidic bond. In sucrose, the reducing groups of both glucose (C1) and fructose (C2) are involved in linkage, making it a non-reducing sugar. - Confusing a nucleoside with a nucleotide . Remember that a nucleoside consists only of a base and a sugar. A nucleotide includes a base, a sugar, and a phosphate group. - Assuming denaturation breaks the primary structure of proteins . Denaturation disrupts hydrogen bonds and hydrophobic interactions of secondary and tertiary structures. The covalent peptide bonds of the primary structure remain unaffected. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 12](https://www.swavid.com/cbse/class-12) - [Chemistry](https://www.swavid.com/cbse/class-12/chemistry/chapters) - [Start free →](https://www.swavid.com/signup) - [All 10 chapters](https://www.swavid.com/cbse/class-12/chemistry/chapters) - [NCERT Chemistry Part II (Reprint 2026-27)](https://ncert.nic.in/textbook.php) - [Open notes](https://www.swavid.com/cbse/class-12/chemistry/chapter/aldehydes-ketones-and-carboxylic-acids) - [Open notes](https://www.swavid.com/cbse/class-12/chemistry/chapter/amines) - [Class 12 Chemistry](https://www.swavid.com/cbse/class-12/chemistry/chapters) - [Start free →](https://www.swavid.com/signup)