class 11 chapter biology biomolecules notes

 

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Chapter: Biomolecules – Class 11 Biology

🔹 Introduction

• Biomolecules are organic and inorganic molecules that make up living organisms.

• They are involved in the structure and function of cells.

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🔹 Types of Biomolecules

1. Primary Metabolites

• Found in all cells and have identifiable functions.

• Examples: Sugars, amino acids, vitamins, nucleotides.

2. Secondary Metabolites

• Not found in all cells and are not directly involved in growth.

• Examples: Alkaloids, flavonoids, rubber, essential oils, pigments, drugs, spices.

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🔹 Chemical Composition of Living Tissues

• Elements: C, H, O, N, P, S, Ca, K, etc.

• 96% of body mass: C, H, O, N.

• Use analysis techniques like Kjeldahl method, chromatography, mass spectrometry.

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🔹 Biomacromolecules

• Large-sized molecules with high molecular weight (>1000 Da).

• Categories:

  1. Polysaccharides

  2. Proteins

  3. Nucleic acids

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🔹 Carbohydrates

🔸 Definition:

• Organic compounds of C, H, and O.

• General formula: $C_n(H_2O)_n$

🔸 Types:

1. Monosaccharides – Simple sugars (e.g., glucose, fructose).

2. Oligosaccharides – 2-10 monosaccharide units (e.g., sucrose, maltose).

3. Polysaccharides – Long chains of monosaccharides (e.g., starch, cellulose, glycogen).

🔸 Important Polysaccharides:

• Starch – Storage in plants.

• Glycogen – Storage in animals.

• Cellulose – Structural in plants.

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🔹 Proteins

🔸 Composition:

• Made of amino acids (20 types).

• Peptide bond: joins amino acids.

🔸 Structure Levels:

1. Primary – Sequence of amino acids.

2. Secondary – Folding (α-helix, β-sheet).

3. Tertiary – 3D structure.

4. Quaternary – More than one polypeptide chain.

🔸 Functions:

• Enzymes, hormones, antibodies, structural proteins.

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🔹 Enzymes

🔸 Definition:

• Biological catalysts (proteins) that speed up reactions without being used up.

🔸 Properties:

• Specific, efficient, work at optimal pH & temperature.

🔸 Mechanism:

• Lock and key model or Induced fit model.

🔸 Factors Affecting Activity:

• Temperature, pH, substrate concentration, inhibitors.

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🔹 Lipids

🔸 Structure:

• Composed of fatty acids and glycerol.

🔸 Types:

• Fats (solid at room temp), Oils (liquid).

• Phospholipids – Cell membranes.

• Steroids – Hormones like cholesterol.

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🔹 Nucleic Acids

🔸 Types:

1. DNA (Deoxyribonucleic acid) – Genetic material.

2. RNA (Ribonucleic acid) – Involved in protein synthesis.

🔸 Nucleotide = Nitrogenous base + Sugar + Phosphate

• Bases:

  • Purines: Adenine, Guanine

  • Pyrimidines: Cytosine, Thymine (DNA), Uracil (RNA)

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🔹 Metabolism

🔸 Definition:

• Sum of all biochemical reactions in a cell.

🔸 Types:

1. Anabolism – Building up (e.g., protein synthesis).

2. Catabolism – Breaking down (e.g., respiration).

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🔹 Enzyme Inhibition

• Competitive: Inhibitor competes with substrate.

• Non-competitive: Inhibitor binds elsewhere and changes enzyme shape.

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🔹 Important Formulas

• Glucose molecular formula: $C_6H_{12}O_6$

• Sucrose: Glucose + Fructose

• Peptide bond: Between –COOH of one amino acid and –NH₂ of another.

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