Class 12 Biology – Biomolecules

1. Introduction

• Biomolecules are organic and inorganic molecules present in living organisms.

• They are essential for structure, energy, and regulation of biological processes.

• Broadly classified into carbohydrates, proteins, lipids, nucleic acids, and vitamins.

2. Carbohydrates

• Definition: Organic compounds made of carbon, hydrogen, and oxygen (C, H, O).

• Function: Primary source of energy, structural components, and storage.

• Types:

  • Monosaccharides: Simple sugars (glucose, fructose)

  • Disaccharides: Two sugars joined (sucrose, lactose)

  • Polysaccharides: Many sugars linked (starch, glycogen, cellulose)

• Importance:

  • Provide instant energy

  • Serve as structural material (cellulose in plants)

  • Act as energy storage (starch, glycogen)

3. Proteins

• Definition: Polymers of amino acids, containing carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.

• Function: Structural support, enzymes, transport, hormones, antibodies.

• Levels of Structure:

  • Primary: Sequence of amino acids

  • Secondary: Alpha-helix or beta-pleated sheets

  • Tertiary: 3D folding of protein chain

  • Quaternary: Multiple protein chains together

• Importance:

  • Structural support (keratin, collagen)

  • Catalysis (enzymes)

  • Defense (antibodies)

  • Transport (hemoglobin)

4. Lipids

• Definition: Hydrophobic biomolecules composed mainly of carbon, hydrogen, and a small amount of oxygen.

• Function: Energy storage, cell membrane structure, signaling molecules.

• Types:

  • Fats and oils: Energy storage

  • Phospholipids: Cell membrane structure

  • Steroids: Hormones and signaling

  • Waxes: Protective coatings

• Importance:

  • Long-term energy storage

  • Insulation and protection

  • Cell membrane integrity

5. Nucleic Acids

• Definition: Polymers of nucleotides (sugar + phosphate + nitrogenous base).

• Function: Storage and transmission of genetic information, protein synthesis.

• Types:

  • DNA: Stores genetic information

  • RNA: Helps in protein synthesis

• Importance:

  • Inheritance of traits

  • Protein coding and regulation

6. Vitamins and Minerals

• Vitamins: Organic molecules required in small amounts for metabolism and health.

  • Water-soluble: B-complex, C

  • Fat-soluble: A, D, E, K

• Minerals: Inorganic nutrients needed for enzyme function, bone formation, and osmoregulation.

7. Key Points to Remember

• Carbohydrates: Energy and structural support

• Proteins: Structural, enzymatic, transport, and defense roles

• Lipids: Energy storage, insulation, membrane components

• Nucleic acids: Genetic information and protein synthesis

• Vitamins and minerals: Micronutrients essential for metabolic and regulatory functions

• Biomolecules are essential for life processes, growth, and maintenance of organisms