1.2 - Cell structure and organisation

• Eukaryotic cells


  Cells that contain a nucleus and membrane bound organelles

  
• Ultrastructure of eukaryotic cells


  • Nucleus surrounded by a double membrane called the envelope containing pores
  • Rough endoplasmic reticulum which is a series of flattened sacs enclosed by a membrane with ribosomes on the surface
  • Smooth endoplasmic reticulum which is a system of membrane bound sacs
  • Golgi apparatus which is a series of fluid filled, flattened & curved sacs with vesicles surrounding the edges
  • Mitochondria which are usually oval shaped, bound by a double membrane called the envelope with an inner membrane folded to form cristae and a matrix on the inside
  • Centrioles which are hollow cylinders containing a ring of microtubules arranged at right angles to each other
  • Ribosomes which are composed of two sub-units and are the site of protein production
  • Lysosome which is a vesicle containing digestive enzymes bound by a single membrane
• Prokaryotic cells (e.g. bacteria)


  • Cell wall - Rigid outer covering made of peptidoglycan
  • Capsule - Protective slimy layer which helps the cell to retain moisture and adhere to surfaces
  • Plasmid - Circular piece of DNA
  • Flagellum - A tail like structure which rotates to move the cell
  • Pili - Hair-like structures which attach to other bacterial cells
  • Ribosomes - Site of protein production
  • Mesosomes - Infoldings of the inner membrane which contain enzymes required for respiration
• Viruses


  Non-living structures which consist of nucleic acid (either DNA or RNA) enclosed in a protective protein coat called the capsid, sometimes covered with a lipid layer called the envelope
• Cells of multicellular organisms are organised into tissues, tissues into organs and organs into systems