Biomolecules describe the molecules required by living things to build body parts and maintain the biochemical processes required for life functions

These biomolecules may be classed as either organic or inorganic compounds

  • Organic compounds are compounds containing carbon that are found in living thingsĀ 
    • Except for hydrogen carbonates (HCO3-), carbonates (CO32-) and oxides of carbon (CO, CO2)
  • Inorganic compounds are all other compounds (there are less different inorganic compounds than organic compounds)


Organic molecules can form large and complex biomacromolecules when simple recurring subunits (monomers) are joined together to form polymers

  • Monomers of organic molecules are joined together to form polymers via a condensation reaction, which results in the formation of a water molecule
  • Polymers can be broken down (or hydrolysed) via a hydrolysis reaction, which requires molecules of water to reverse the condensation process

Condensation and Hydrolysis Reactions

There are four main classes of macromolecules: carbohydrates, lipids, nucleic acids and proteins

  • Autotrophs synthesise their own organic molecules from inorganic compounds they take in from the surrounding environment (e.g. photosynthesis)
  • Heterotrophs synthesise necessary organic molecules from other organic molecules consumed as part of their diet

Classes of Macromolecules

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