Organic Macromolecules: Comprehensive Study Notes

Organic Macromolecules: Comprehensive Study Notes

Introduction to Organic Macromolecules

• Four Major Classes: Organic macromolecules are essential for life and include: Carbohydrates, Proteins, Lipids, and Nucleic Acids (such as DNA).
• Monomers and Polymers: Many macromolecules are polymers, which are large molecules built from repeating smaller units called monomers.
  • Examples:
    • Proteins are polymers of amino acid monomers.
    • Carbohydrates are polymers of monosaccharide monomers.
    • Nucleic acids (DNA, RNA) are polymers of nucleotide monomers.
  • Exception: Lipids are large molecules but are generally not considered polymers because they are not made of many repeating identical subunits.

Chemical Processes for Macromolecule Formation and Breakdown

• Dehydration Synthesis (Condensation Reaction):
  • Process by which two monomers are joined together to form a larger molecule by the removal of a water molecule ($H_2O$).
  • This is how complex molecules like disaccharides and polysaccharides are built from simpler sugar units.
• Hydrolysis:
  • The reverse process of dehydration synthesis.
  • A larger molecule is broken down into smaller subunits by the addition of a water molecule ($H_2O$).
  • This is the primary chemical process of digestion, breaking down food molecules into absorbable units.

Carbohydrates

• Definition: Sugars, often recognized by names ending in "-ose" (e.g., glucose, fructose, lactose).
• Elements: Contain Carbon (C), Hydrogen (H), and Oxygen (O).
• Ratio: Generally follow a rough $1:2:1$ ratio of C:H:O (e.g., $C<em>6H</em>{12}O_6$ for simple sugars).
  • Note on Disaccharides: When two monosaccharides combine via dehydration synthesis, a water molecule is removed. Therefore, the exact $1:2:1$ ratio might be slightly altered in larger carbohydrates (e.g., sucrose is $C<em>{12}H</em>{22}O_{11}$, which is close but not exactly $1:2:1$).
• Monomer: Monosaccharides.

Monosaccharides (Simple Sugars)

• Smallest Type: The basic building blocks of all carbohydrates.
• Examples:
  • Glucose
  • Fructose
  • Galactose
• Isomers: Glucose, fructose, and galactose are isomers of each other.
  • Definition of Isomer: Molecules that have the same molecular formula but different structural arrangements of their atoms.
  • Molecular Formula: Tells you the types and number of atoms in a molecule (e.g., $C<em>6H</em>{12}O_6$ for glucose, fructose, galactose).
  • Structural Formula: Shows the arrangement of atoms within a molecule, explaining why isomers with the same molecular formula have different properties.
  • Though all taste sweet, their chemical and physical properties differ slightly due to structural variations.
• Carbon Skeleton: In diagrams of organic compounds, carbon atoms (which form the main skeleton/framework) are often not explicitly shown to simplify the diagram; their presence at vertices and ends is assumed.
• Galactose and the Milky Way Connection:
  • The ancient Greek word for milk had the root galacto.
  • The