IB Biology SL

Revision Notes

2.1.2 Metabolism

Metabolism

Metabolism means ALL the reactions that take place in organisms

  • Metabolism is a catch-all term to group all the chemical reactions that take place within cells and organisms
  • Metabolism can be thought of as the chemical reactions of life
  • The molecules involved are metabolites
  • Many reactions of metabolism take place in multiple stages
  • Each stage is catalysed by a separate enzyme
  • A series of interlinked metabolic reactions is called a pathway
  • Metabolic reactions can be classified broadly as anabolic or catabolic

Anabolism

Anabolic reactions

  • Are involved with building up large molecules from smaller ones
  • Examples include
    • Photosynthesis, where CO2 and water are built up into complex sugars
    • Protein synthesis, where amino acids are joined together in sequence
    • The buildup of fat stores ahead of animal hibernation
  • Anabolic reactions often include condensation reactions
  • Anabolic reactions are endergonic (they require an input of energy to take place)
    • energy-storing products are the end result

Catabolism

Catabolic reactions

  • Are involved with breaking down large molecules into smaller ones
  • Often for the purposes of releasing energy for cellular processes and for excretion of waste
  • Examples include
    • Respiration, where CO2 and water are produced from the breakdown of sugars
    • Deamination of proteins to release urea
    • The depletion of fat stores during animal hibernation
  • Catabolic reactions often include hydrolysis reactions
  • Catabolic reactions are exergonic (free energy is released for cellular processes or as excess heat)

Comparison of Anabolism and Catabolism table

 

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