Noncovalent Interactions in Large Molecules (College Board AP® Chemistry)

Noncovalent Interactions in Large Molecules

• Many substances with very large molecular weight make up the structure of living organisms and tissues

• Some examples include starch and cellulose, which abound in plants, as well as proteins, which are found in both plants and animals

  • These molecules are known as polymers and are made of smaller molecules called monomers

Chemical Structures of Starch and Cellulose

Diagram showing the structures of the starch polymer made from the α-glucose monomers while the cellulose polymer is made from β-glucose monomers

• Some important noncovalent interactions which occur in large molecules include:

  • Hydrogen bonding

    • Involves interaction between the polar hydrogen atom from an O-H or N-H bond and the lone electron pairs of very electronegative atoms such as nitrogen, oxygen and fluorine

  • Electrostatic/Ionic interactions

    • These are attractive interactions observed in molecules with permanent dipoles

  • Hydrophobic interactions

    • These interactions are seen between nonpolar molecules and polar molecules such as water

    • It explains why large biomolecules like oils do not dissolve in water

  • Van der Waals interactions

    • A type of interaction that involves polar molecules with permanent dipoles (dipole-dipole) or nonpolar molecules with induced dipoles

  • Some of these interactions have been studied and shown to be present between proteins and phenolic compounds found in plant-based foods

    • These interactions can affect the nutritional properties of food

Noncovalent Interactions between Proteins and Ferulic Acid

Diagram showing possible non-covalent interactions between proteins and Ferulic acid