Organic Molecules and Their Functional Groups

Understanding Organic Molecules

  • Organic vs Inorganic Molecules
    • An organic molecule contains at least both carbon (C) and hydrogen (H).
    • Example: Methane (CH₄) is organic because it has C and H.
    • Carbon Dioxide (CO₂) is not organic despite being produced by living organisms, as it lacks hydrogen.

Monomers and Polymers

  • Monomers: Single subunits that can join together to form larger structures.
  • Polymers: Though made up of repeated units of the same monomer.
    • Building Polymers: This process involves chemical reactions to link monomers.
    • Breaking Down Polymers: Uses different reactions to separate monomers.

Four Classes of Biological Molecules

  1. Carbohydrates
  2. Lipids
  3. Proteins
  4. Nucleic Acids
  • Focus on understanding Carbohydrates first before proceeding to other macromolecules.

Importance of Carbon in Organic Molecules

  • Carbon can form four covalent bonds, leading to diverse structures and combinations, making it the backbone of organic chemistry.
  • Bonding variations include single, double, or triple bonds with other atoms.
  • Can create complex ring structures and chains, essential for biological molecule diversity.

Functional Groups in Organic Chemistry

  • Definition: A functional group is a specific group of atoms that imparts characteristic properties and behaviors to a molecule regardless of its structure.
  • Significance: Understanding functional groups allows prediction of molecular behavior, including solubility and reactivity.

Common Functional Groups

  1. Hydroxyl (-OH)

    • Polar and hydrophilic, often found in alcohols and carbohydrates (e.g., glucose).
    • Provides water-solubility due to its polar nature.

  2. Methyl (-CH₃)

    • Nonpolar and hydrophobic.
    • Common in organic molecules such as fatty acids.

  3. Carboxyl (-COOH)

    • Contains both a carbonyl and a hydroxyl group.
    • Makes compounds acidic as it can donate a proton (H⁺) in water.
    • Found in organic acids such as acetic acid (vinegar).

  4. Amino (-NH₂)

    • Acts as a base, can pick up protons in solution to become positively charged (NH₃⁺).
    • Common in amino acids, which are the building blocks of proteins.

  5. Phosphate (-PO₄)

    • Important for energy transfer (e.g., ATP) and in DNA and RNA structure.
    • Generally charged, making it hydrophilic.

  6. Sulfhydryl (-SH)

    • Important in protein structure (e.g., cysteine).
    • Can form disulfide bonds which are important for protein stability.

Reactions Involving Polymers

  • Dehydration Synthesis (Condensation Reaction)

    • Combines monomers by removing water, forming a covalent bond and producing a polymer.

  • Hydrolysis

    • Breaks down polymers by adding water to separate monomers, reversing the dehydration synthesis action.

Carbohydrates – Structure and Function

  • Carbohydrates consist only of carbon, hydrogen, and oxygen in the ratio of 1:2:1.
  • Monomer: Monosaccharide (simple sugars like glucose, fructose).
    • Disaccharides: Formed by joining two monosaccharides (e.g., sucrose, lactose).
    • Polysaccharides: Large polymers made up of many monosaccharides (e.g., starch, cellulose).
  • Main functions include energy storage (starch and glycogen) and structural roles (cellulose in plants).

Summary of Functional Roles of Carbohydrates

  • Primary source of energy (quick energy from sugars).
  • Serve as energy reserves (starch in plants, glycogen in animals).
  • Provide structural support in plants (e.g., cellulose).
  • Recognizable by the suffix -ose.
  • Generally polar and hydrophilic, vital to biological processes.