Bacterial Cells (Cambridge O Level Biology)

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Bacteria Cells

  • Bacteria, which have a wide variety of shapes and sizes, all share the following biological characteristics:
    • They are microscopic single-celled organisms
    • Possess a cell wall (made of peptidoglycan, not cellulose), cell membrane, cytoplasm and ribosomes
    • Lack a nucleus but contain a circular chromosome of DNA that floats in the cytoplasm
    • Plasmids are sometimes present - these are small rings of DNA (also floating in the cytoplasm) that contain extra genes to those found in the chromosomal DNA
    • They lack mitochondria, chloroplasts and other membrane-bound organelles found in animal and plant cells
  •  Some bacteria also have a flagellum (singular) or several flagella (plural). These are long, thin, whip-like tails attached to bacteria that allow them to move
  • Examples of bacteria include:
    • Lactobacillus (a rod-shaped bacterium used in the production of yoghurt from milk)
    • Pneumococcus (a spherical bacterium that acts as the pathogen causing pneumonia)

A typical bacterial cell

A typical bacterial 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