Cell Theory (Edexcel A (SNAB) A Level Biology)

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Cara Head

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Cara Head

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Cell Theory

  • Until microscopes became powerful enough to view individual cells, no-one knew for certain what living organisms were made from
  • A scientist called Robert Hooke is thought to be the first person to view cells, using the term 'cell' to describe these newly discovered structures
  • Matthias Schleiden and Theodor Schwann were two other scientists who studied animal and plant cells
    • In 1837 they came up with the idea that all living organisms are made of cells
    • This idea is known as ‘cell theory’
    • The cell theory is a unifying concept in biology, meaning that it is universally accepted
  • Cell theory includes three main ideas
    • All living organisms are made up of one or more cells
    • Cells are the basic functional unit in living organisms
    • New cells are produced from pre-existing cells
  • The cells of all living organisms share some common features
    • Cell surface membrane
    • Cytoplasm
    • DNA
    • Ribosomes
  • Beyond these common features different cell types contain different structural elements and combinations of organelles, e.g.
    • Prokaryotic cells have no internal membranes and smaller ribosomes
    • Eukaryotic cells have several internal membrane-bound organelles and larger ribosomes
  • When examined under a microscope it is possible to see the ultrastructure of different cell types
    • Cell ultrastructure refers to the internal structures of the cell

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Cara Head

Author: Cara Head

Expertise: Biology

Cara graduated from the University of Exeter in 2005 with a degree in Biological Sciences. She has fifteen years of experience teaching the Sciences at KS3 to KS5, and Psychology at A-Level. Cara has taught in a range of secondary schools across the South West of England before joining the team at SME. Cara is passionate about Biology and creating resources that bring the subject alive and deepen students' understanding