IB Biology SL

Revision Notes

2.7.1 Cellular Respiration

The Four Stages in Aerobic Respiration

  • Glucose is the main respiratory substrate used by cells
  • Aerobic respiration is the process of breaking down a respiratory substrate in order to produce ATP using oxygen
  • The process of aerobic respiration using glucose can be split into four stages
  • Each stage occurs at a particular location in a eukaryotic cell:
    • Glycolysis takes place in the cell cytoplasm
    • The Link reaction takes place in the matrix of the mitochondria
    • The Krebs cycle takes place in the matrix of the mitochondria
    • Oxidative phosphorylation occurs at the inner membrane of the mitochondria

Four Stages of Respiration Table

Four Stages of Respiration Table, downloadable AS & A Level Biology revision notes

Exam Tip

It’s important to know the exact locations of each stage. It is not enough to say the Krebs cycle takes place in the mitochondria, you need to say it takes place in the matrix of the mitochondria.

The Vital Role of ATP

  • All organisms require a constant supply of energy to maintain their cells and stay alive
  • This energy is required:
    • In anabolic reactions – building larger molecules from smaller molecules
    • To move substances across the cell membrane (active transport) or to move substances within the cell
    • In animals, energy is required:
      • For muscle contraction – to coordinate movement at the whole-organism level
      • In the conduction of nerve impulses, as well as many other cellular processes
  • In all known forms of life, ATP from respiration is used to transfer energy in all energy-requiring processes in cells
  • This is why ATP is known as the universal energy currency
  • Adenosine Triphosphate (ATP) is a nucleotide
    • The monomers of DNA and RNA are also nucleotides

 

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