Edexcel A (SNAB) A Level Biology

Revision Notes

7.2.2 Stages of Respiration

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Stages of Respiration

  • Glucose is broken down in stages, each of which consists of a series of chemical reactions
  • These chemical reactions are controlled by intracellular enzymes that catalyses reactions within the cell
  • This ensures that the energy trapped within the chemical bonds of the glucose molecule is released gradually and not all at once
  • A sudden release of such a large amount of energy would result in an increase in body temperature to levels that would denature enzymes
  • Each stage of aerobic respiration 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

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.

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Marlene

Author: Marlene

Marlene graduated from Stellenbosch University, South Africa, in 2002 with a degree in Biodiversity and Ecology. After completing a PGCE (Postgraduate certificate in education) in 2003 she taught high school Biology for over 10 years at various schools across South Africa before returning to Stellenbosch University in 2014 to obtain an Honours degree in Biological Sciences. With over 16 years of teaching experience, of which the past 3 years were spent teaching IGCSE and A level Biology, Marlene is passionate about Biology and making it more approachable to her students.