Introduction to Biological Macromolecules

Biological Monomers and Polymers

• Monomer Definition: Chemical subunits used to create polymers; repeating units that construct macromolecular structures.

• Polymer Definition: Chain-like macromolecules consisting of similar or identical repeating units covalently bonded together.

• Structural Properties:

  • All monomers contain carbon and serve as essential building blocks for biological molecules.

  • Covalent bonds connect all monomers within a polymer chain.

  • Polymers are specific to the unique monomers of which they consist.

Classes of Biological Macromolecules

• Four Major Classes:

  • Carbohydrates

  • Proteins

  • Nucleic Acids

  • Lipids

• Classification of Polymers vs. Non-Polymers:

  • Carbohydrates, proteins, and nucleic acids are true polymers formed from repeating monomer units.

  • Lipids do not contain true monomers, do not form true polymers, and are hydrophobic molecules.

• Polymer and Monomer Relationships:

  • Carbohydrates: Monosaccharides are the monomers that build carbohydrate polymers.

  • Proteins: Amino acids are the monomers that build protein polymers.

  • Nucleic Acids: Nucleotides are the monomers that build nucleic acid polymers.

  • Lipids: Fatty acids are key component subunits, though lipids lack true monomer-polymer structures.

Chemical Elements in Biological Macromolecules

• Molecular Diversity via Carbon:

  • Carbon forms the fundamental backbone of biological macromolecules.

  • Variations in carbon skeletons allow for extensive molecular diversity.

  • Carbon is present in all biological monomers and enables the formation of large macromolecules.

• Nitrogen ($N$):

  • An essential element required for building proteins and nucleic acids.

• Phosphorus ($P$):

  • An essential element required for building nucleic acids and certain lipids (e.g., phospholipids).

• Sulfur ($S$):

  • An essential element utilized specifically in the building of proteins.

Synthesis and Breakdown of Macromolecules

• Polymerization:

  • The chemical process of connecting many monomers together to form a polymer chain.

• Dehydration Synthesis (Dehydration Reaction):

  • Reaction used to construct biological macromolecules from monomer units.

  • Covalently bonds two monomers together while releasing a water molecule ($H_2O$).

  • Mechanism:

  • The hydroxyl group ($-OH$) of one monomer bonds to the hydrogen atom ($-H$) of another monomer.

  • This interaction forms a water molecule ($H_2O$), which is released as a byproduct.

  • General chemical equation: $A + B \rightarrow AB + H_2O$

• Hydrolysis Reaction:

  • Reaction used to break down biological macromolecules into their constituent monomers.

  • Cleaves the covalent bonds within a polymer by utilizing a water molecule ($H_2O$).

  • Mechanism:

  • One hydrogen atom ($-H$) from the water molecule attaches to one monomer.

  • The remaining hydroxyl group ($-OH$) from the water molecule attaches to the adjacent monomer.

  • General chemical equation: $AB + H_2O \rightarrow A + B$