BIOMOLECULES

Biological Molecules Overview

  • Biological molecules are complex and essential for life processes.

  • Composed mainly of carbon and hydrogen, with nitrogen, oxygen, sulfur, and phosphorus.

  • Four major classes: carbohydrates, lipids, proteins, and nucleic acids.

Objectives

  • Categorize biological molecules based on structure and function.

  • Explain the role of each biological molecule in metabolic processes.

Biomolecules Definition

  • Living systems consist of nonliving atoms and molecules that form complex biomolecules.

  • These biomolecules interact to constitute the molecular logic of life processes.

Carbohydrates

  • Composed of carbon, hydrogen, and oxygen.

  • Roles of Carbohydrates:

    • Chief energy source for organisms.

    • Backbone of other organic molecules (e.g., DNA, RNA).

    • Chemical energy storage (starch in plants, glycogen in animals).

    • Structural components (cellulose in plants, chitin in animals).

    Classification of Carbohydrates

    1. Monosaccharides (C6H12O6)

      • Examples: Glucose, Galactose, Fructose

      • Use: Building blocks for more complex sugars; serve as immediate energy sources for cells.

    2. Disaccharides (C12H22O11)

      • Examples: Sucrose (table sugar), Lactose (milk sugar), Maltose

      • Use: Formed from two monosaccharides through dehydration synthesis; provide energy and are broken down via hydrolysis.

    3. Oligosaccharides

      • Examples: Raffinose, Maltotriose

      • Use: Composed of 3 to 20 sugar units; involved in cell recognition and can serve as energy sources.

    4. Polysaccharides

      • Examples: Starch (energy storage in plants, composed of 2 substances: amylose, amylopectin that can be digested by the enzyme “amylase)

      • Glycogen (energy storage in animals, found in the liver and muscles)

      • Cellulose (structural component in outer wall of plant cell walls which used for support and protection, can be broken down by enzyme “cellulase”)

      • Chitin (Rigid, hard and inflexible, functions as support and protection in outer coverings of insects and crustaceans)


      • Use: Composed of more than 20 sugar units; serve various roles in energy storage and structural support.

    • Serve various roles in energy storage and structural support.

Lipids

  • Diverse group of nonpolar biological molecules, insoluble in water (hydrophobic).

  • Important types include: fats, phospholipids, steroids.

Classification of Lipids

  1. Fatty Acids

    • Essential Fatty Acids: Not synthesized by the body; must be consumed.

    • Non-essential Fatty Acids: Synthetized by the body.

    • Types:

      • Saturated Fats: Single bonds, solid at room temperature.

      • Unsaturated Fats: Double bonds, liquid at room temperature.

      • Trans Fats: Produced via hydrogenation; linked to health risks.

  2. Triacylglycerol (TAG)

    • Long-term energy storage; provides insulation and protects organs (stored in adipose tissue)

  3. Waxes

    • Energy storage for plankton; water-repellant properties.

  4. Phospholipids

    • Major component of cell membranes; forms bilayer structure that serves as barrier between the cell and its surroundings, has hydrophilic (polar) head and two (nonpolar) hydrophobic tails.

  5. Steroids

  • Involved in signaling (e.g., hormones); maintain cell membrane structure.

  • Types:

  • Bile Acids: acts as emulsifying agent in digestive system.

  • Cholesterol: regulates the fluidity of the cell membrane, starting point for the synthesis of other steroids.

  • Steroidal hormones: hormones derived from cholesterol that act as chemical messengers in the body. (Male - Androgen and Testosterone) (Female - Estrogen and Progesterone)

Proteins

  • Proteins make up over half of solid matter in cells; known as the building blocks of life.

  • Functions of Proteins:

    1. Enzymatic: Catalyze biochemical reactions.

    2. Defensive: Protect against disease (e.g., antibodies).

    3. Storage: Reservoir for metal ions and amino acids (e.g., casein, ovalbumin).

    4. Transport: Facilitate movement of molecules (e.g., hemoglobin).

    5. Hormonal: Regulate physiological processes (e.g., insulin).

    6. Receptor: Respond to chemical signals.

    7. Contractile: Enable movement (e.g., actin, myosin).

    8. Structural: Provide support and shape (e.g., collagen, keratin).

Levels of Protein Structure

  1. Primary Structure: Linear sequence of amino acids.

  2. Secondary Structure: Patterns formed by hydrogen bonds (alpha helix, beta sheets).

  3. Tertiary Structure: Three-dimensional shape formed by side-chain interactions.

  4. Quaternary Structure: Combination of multiple polypeptide chains.

Denaturation of Proteins

  • Disorganization of protein shape leading to loss of function due to denaturing agents.

  • Denaturing agents- reagents or conditions that brought the unfolding of a protein

Amino Acids

  • Building blocks of proteins.

  • Contain carbon, hydrogen, oxygen, and nitrogen atoms.

  • Essential for protein synthesis.

Classification of Amino Acids

  • Based on side chains:

    • Nonpolar: Hydrophobic & low solubility in water.

    • Polar: Hydrophilic & highly soluble in water.

    • Electrically Charged: Involved in enzyme reactions.

  • Based on synthesis:

    • Essential: Must be obtained through diet.

    • Non-Essential: Can be synthesized by the body.

Enzymes

  • Biological catalysts, usually proteins, that accelerate chemical reactions.

  • Functions:

    • Break down large molecules.

    • Aid in energy generation (e.g., ATP synthase).

    • Assist in ion movement across membranes.

How Enzymes Work

  • Enzymes lower activation energy required for reactions.

  • Active Site: Where substrates bind and reactions occur.

  • Substrates: Molecules the enzyme acts upon.

Theories of Enzyme Action

  • Lock-and-Key Model and Induced Fit Theory (adjustments made for optimal fit).

Factors Affecting Enzyme Activity

  • Substrate Concentration: Affects reaction rate until saturation.

  • Enzyme Concentration: More enzymes increase reaction speed.

  • Temperature: Optimal temperature increases activity; extreme heat denatures enzymes.

  • pH Levels: Each enzyme has an optimal pH range.

  • Inhibitors: Substances that reduce enzyme activity.

Types of Inhibitors

  1. Competitive Inhibitors: Compete with substrate for active site.

  2. Non-competitive Inhibitors: Bind to allosteric site, affecting enzyme shape.

  3. Uncompetitive Inhibitors: Bind only to enzyme-substrate complex.

Nucleic Acids

  • Macromolecules made of nucleotides (DNA and RNA).

  • Enable reproduction of complex components across generations.

Structure of DNA and RNA

  • DNA: Genetic material, composed of deoxyribose sugar and nitrogen bases (A, T, G, C). Strands are antiparallel with phosphodiester bonds.

  • RNA: Contains ribose sugar, uracil replaces thymine, usually single-stranded.

Types of RNA

  1. Messenger RNA (mRNA): Template for protein synthesis.

  2. Transfer RNA (tRNA): Transfers amino acids during translation.

  3. Ribosomal RNA (rRNA): Component of ribosomes.