2.1  Molecules to Metabolism

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Essential Idea:

Living organisms control their composition 

by a complex web of chemical reactions


  • Molecular biology explains living processes in terms of the chemical substances involved
  • Carbon atoms can form four covalent bonds allowing a diversity of stable compounds to exist
  • Life is based on carbon compounds including carbohydrates, lipids, proteins and nucleic acids
  • Metabolism is the web of all the enzyme-catalysed reactions in a cell or organism
  • Anabolism is the synthesis of complex molecules from simpler molecules including the formation of macromolecules from monomers by condensation reactions
  • Catabolism is the breakdown of complex molecules into simpler molecules including the hydrolysis of macromolecules into monomers


  • Urea as an example of a compound that is produced by living organisms but can also be artificially synthesized


  • Drawing molecular diagrams of glucose, ribose, a saturated fatty acid and a generalised amino acid
  • Identification of biochemicals such as sugars, lipids or amino acids from molecular diagrams