# Biomolecules Notes, Class 11 Biology | SwaVid Biomolecules, NCERT Class 11 Biology: notes with key ideas, key terms, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-11/biology/chapter/biomolecules Source: https://www.swavid.com/cbse/class-11/biology/chapter/biomolecules # Biomolecules ## Key terms ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 11 Biology on SwaVid ### Analysis of chemical composition ### Amino acids and proteins ### Lipids and polysaccharides ### Nucleic acids ### Dynamic state and metabolism ### Enzymes and their action ### Enzyme inhibition and cofactors ### Next chapter ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 11 › Biology › Biomolecules Notes written by SwaVid from the NCERT textbook. Class 11 Biology, Chapter 9. Key ideas, formulas and common mistakes. CBSE prints 15 marks for Unit III, not for this chapter alone. Short answer. This chapter describes the chemical composition, structure, and functions of biomolecules found in living organisms. It explains how small micromolecules form complex macromolecules like proteins, nucleic acids, and polysaccharides, and details how enzymes catalyse biochemical reactions. Source: NCERT Biology (Reprint 2026-27) , Chapter 9, Biomolecules Living tissue ground in trichloroacetic acid separates into an acid-soluble pool containing micromolecules and an acid-insoluble fraction containing macromolecules. Ash analysis reveals inorganic elements such as calcium and magnesium, while inorganic compounds like sulphates and phosphates are seen in the acid-soluble fraction. Amino acids are organic compounds containing an amino group and an acidic carboxyl group on the alpha-carbon. They link by peptide bonds to form proteins, which exhibit primary, secondary, tertiary, and quaternary structural organisations. Lipids are water-insoluble compounds with molecular weights not exceeding 800 Da, yet they appear in the acid-insoluble pellet because cell membranes fragment into insoluble vesicles. Polysaccharides are long chains of monosaccharides linked by glycosidic bonds, such as cellulose, starch, and glycogen. Nucleic acids are polymers of nucleotides composed of a nitrogenous base, a pentose sugar, and a phosphate group linked by phosphodiester bonds. In B-DNA, two antiparallel polynucleotide chains form a double helix with complementary base pairing. Biomolecules constantly transform into other biomolecules through metabolic reactions happening in living systems. The steady state of a living organism is a non-equilibrium state driven by continuous work, and living processes cannot exist at equilibrium. Enzymes are protein catalysts that lower the activation energy of chemical reactions without being consumed. Substrates bind to the active site to form a transient enzyme-substrate complex, which yields products and frees the enzyme. In competitive inhibition, a substance closely resembling the substrate binds to the active site and reduces the activity, such as malonate inhibiting succinic dehydrogenase. Many enzymes require non-protein cofactors like prosthetic groups, coenzymes, or metal ions to become catalytically active. Try each question first. Then tap it to see the answer. Distance between two successive base pairs in B-DNA = 0.34 nm Total length = 30 × 0.34 nm = 10.2 nm 10.2 nm Succinate is the natural substrate for succinic dehydrogenase. Malonate closely resembles succinate in chemical structure and binds reversibly to the active site. This prevents succinate from binding, thereby reducing enzyme activity. Structural similarity to substrate succinate leads to competition for the active site The protein portion is the apoenzyme and the non-protein constituent is the cofactor. Zinc forms coordination bonds with side chains at the active site in carboxypeptidase. Therefore, zinc is a metal ion cofactor. Apoenzyme and cofactor; zinc is a metal ion Cell Cycle and Cell Division . Cell: The Unit of Life . Respiration in Plants . The 19 chapters of Class 11 Biology . CBSE does not give marks to one chapter. It prints 15 marks for Unit III, Cell: Structure and Function, which includes Biomolecules. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Cell Cycle and Cell Division. 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. - Ch 9 NCERT book - 15 marks, Unit III - 3 quick checks - Classifying lipids as macromolecules because they occur in the acid-insoluble fraction . Remember that lipids have a molecular weight under 800 Da. They separate into the acid-insoluble pellet only because membrane structures break into insoluble lipid vesicles during grinding. - Confusing a nucleoside with a nucleotide . A nucleoside contains only a nitrogenous base attached to a pentose sugar. A nucleotide contains a nucleoside plus a phosphate group. - Believing living systems function at chemical equilibrium . Living systems maintain a steady, non-equilibrium state. Reaching equilibrium means zero free-energy change, which halts all biological work and leads to death. - Confusing coenzymes with prosthetic groups . Prosthetic groups are organic compounds tightly bound to the apoenzyme, such as haem in peroxidase. Coenzymes are organic compounds whose association with the apoenzyme is only transient during catalysis. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 11](https://www.swavid.com/cbse/class-11) - [Biology](https://www.swavid.com/cbse/class-11/biology/chapters) - [Start free →](https://www.swavid.com/signup) - [All 19 chapters](https://www.swavid.com/cbse/class-11/biology/chapters) - [NCERT Biology (Reprint 2026-27)](https://ncert.nic.in/textbook.php) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/cell-cycle-and-cell-division) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/cell-the-unit-of-life) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/respiration-in-plants) - [Class 11 Biology](https://www.swavid.com/cbse/class-11/biology/chapters) - [Start free →](https://www.swavid.com/signup)