Introduction to Macromolecules

  • Carbon-based molecules are essential for life.
  • Elements such as silicon are considered for hypothetical non-carbon-based life due to tetravalence.

Properties of Carbon

  • Carbon is tetravalent, capable of forming four covalent bonds.
  • Allows the formation of large, complex molecules (e.g. proteins, DNA, carbohydrates, lipids).
  • Carbon forms covalent bonds only, never ionic bonds.

Structure and Versatility of Carbon

  • Carbon can form long chains, branched structures, or ring structures.
  • Double or triple bonds modify carbon connectivity and molecular properties.
  • Each carbon atom in chains or rings forms four bonds total (including multiple bonds).

Functional Groups

  • Functional groups impart specific properties to carbon-based molecules:
    • Hydroxyl group (–OH): polar, increases solubility in water.
    • Methyl group (–CH₃): non-polar, hydrophobic.
    • Carbonyl group (C=O): present in sugars and proteins.
    • Carboxyl group (-COOH): polar, acidic.
    • Amino group (-NH₂): polar, basic.
    • Phosphate group (–PO₄): polar, involved in energy transfer (ATP, DNA).

Macromolecules

  • Carbohydrates:

    • Basic unit: Monosaccharides (e.g. glucose, fructose).
    • Two monosaccharides: Disaccharides (e.g. sucrose).
    • Many monosaccharides: Polysaccharides (e.g. glycogen).

  • Lipids:

    • Basic unit: Glycerol + three fatty acids (triglycerides).
    • Phospholipids consist of glycerol, two fatty acids, and a phosphate group.

  • Proteins:

    • Made up of amino acids (with amino and carboxyl functional groups).

  • Nucleic Acids:

    • Made of nucleotides (comprised of a sugar, phosphate group, and nitrogenous base).

Polymerization Reactions

  • Macromolecules are polymers formed from repeated subunits (monomers).
  • Dehydration synthesis: Links monomers by removing water (forming covalent bonds).
  • Hydrolysis: Breaks polymers into monomers by adding water.

Energy Storage

  • Fats (lipids) store more energy per gram (9 kcal) than carbohydrates (4 kcal).
  • Carbohydrates primarily serve as short-term energy stores; fats serve longer-term energy storage.

Summary of Monosaccharides and Linkages

  • Monosaccharides (C₆H₁₂O₆) can link to form disaccharides and polysaccharides with specific bond types (e.g. alpha, beta linkages).
  • Importance in energy metabolism, structural support (like cellulose in wood).

Conclusion

  • Understanding carbon's properties and functionality of different macromolecules is crucial to biology.