Syllabus Edition

First teaching 2023

First exams 2025

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General Cell Structure (SL IB Biology)

Revision Note

Cara Head

Author

Cara Head

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General Cell Structure

  • All living organisms are comprised of cells
  • These cells all have some common unifying features, including
    • DNA as genetic material
    • Cytoplasm 
    • A plasma membrane

DNA

  • All living cells contain some sort of DNA, this varies between eukaryotic cells and prokaryotic cells
  • The presence of DNA means that a new cell can be formed from an old cell, as genetic material is able to be stored and transferred
  • DNA also controls the production of enzymes and other vital proteins within the cell

Cytoplasm

  • Cytoplasm is found within the boundary of a cell
  • It is composed of mainly water with dissolved substances, such as ions
  • The fluid is known as cytosol
  • Many of the cell's important reactions take place within the cytoplasm

Plasma membrane

  • The plasma membrane surrounds the cell and encloses all the cell contents
  • In all cell types, the plasma membrane has two layers and this is called a bilayer
  • The bilayer consists of lipids; these vary depending on the type of organism 
  • The membrane is responsible for controlling the interactions of the cell's interior with the exterior
    • Materials required by the cell are transported into the cell interior
    • Waste substances are exported out of the cell to the surrounding environment
  • The membrane is studded with proteins which have varying functions including:
    • Cell recognition
    • Cell communication
    • Transport into and out 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