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Biological Molecules

Objectives

• Chemical Elements: Study the elements that make up carbohydrates, fats, and proteins.

• Subunits of Biological Molecules: Understand the monomers that form biological macromolecules.

• Food Tests: Learn how to test for starch, reducing sugars, proteins, fats, oils, and vitamin C.

• Role of Water: Explore the significance of water as a solvent in biological processes.

Biological Molecules

• Macromolecules: Large organic molecules formed by the process of polymerization.

  • Polymerization: Joining smaller units (monomers) through covalent bonds.

  • Essential macromolecules: include proteins, nucleic acids, carbohydrates, and lipids.

Biochemical Processes

• Living organisms rely on biochemical processes involving chemical reactions between compounds.

• Six elements constitute 99% of living tissue: C, H, O, N, P, S, forming the basis of cellular function.

Carbon

• Key Characteristics:

  • Carbon has 4 valence electrons, allowing it to form four covalent bonds.

  • Forms stable and complex structures known as organic molecules.

Organic vs. Inorganic Molecules

• Organic Molecules: Contain carbon (e.g., carbohydrates, lipids, proteins).

• Inorganic Molecules: Do not contain carbon (e.g., water, minerals).

  • Water is the most critical inorganic molecule for living organisms.

Biomolecules are Macromolecules

• Definition of Biomolecules: Also referred to as giant molecules made from smaller molecules.

• Polymerization Process: Building large compounds by joining smaller units called monomers to form polymers.

Classes of Organic Molecules

1. Carbohydrates

2. Lipids

3. Proteins

4. Nucleic Acids

Carbohydrates

• Composition: Chains of carbon, hydrogen, and oxygen (C, H, O); includes hydroxyl groups (-OH).

• Function: Main energy source for organisms; structural support for plants (cellulose) and storage (starch in plants, glycogen in animals).

Types of Carbohydrates

• Monosaccharides:

  • Simple sugars; monomers of carbohydrates (e.g., glucose, galactose, fructose).

• Disaccharides:

  • Two monosaccharides joined together (e.g., sucrose = glucose + fructose).

• Polysaccharides:

  • Large polymers formed from multiple monosaccharides (e.g., cellulose, starch, glycogen).

Simple Carbohydrates

• Sugars: Formed when two monosaccharides undergo dehydration reactions, releasing a water molecule.

• Hydrolysis: Reverse reaction requiring a water molecule to break covalent bonds.

• Examples:

  • Sucrose (table sugar) formed from glucose and fructose.

Functions of Polysaccharides

• Cellulose: Provides structural support in plants.

• Starch: Serves as an energy storage in plant cells.

• Glycogen: Main energy storage polysaccharide in animals.

Lipids

• Properties: Not soluble in water (hydrophobic); primarily composed of C and H atoms.

• Function: Energy storage, biological membranes, insulation, and waterproofing.

• Types of Lipids:

  • Fats: Saturated (single C-C bonds) and unsaturated (one or more C=C double bonds).

  • Oils: Liquid at room temperature, usually from plants.

  • Waxes & Steroids: Specialized types of lipids.

Nucleic Acids

• Function: Store and transmit genetic information.

• Components: Contain H, O, N, C, and P; monomers are nucleotides.

• Types:

  • DNA (double helix) and RNA.

Proteins

• Composition: Contain N, C, H, O; made of amino acids.

• Structure:

  • Four levels: primary (chain of amino acids), secondary (twisted/pleated), tertiary (3D structure), and quaternary (multiple chains).

• Functions:

  • Catalysts (enzymes), structural roles (collagen), transport, muscle formation, cell regulation.

Enzymes

• Role: Biological catalysts that increase reaction rates by lowering activation energy.

Composition of the Cell

• Major components:

  • Water: 70%

  • Fats: 10%

  • Proteins: 15%

  • Nucleic acids: 4%

  • Carbohydrates: 1%

Summary Table