Specialised cells

• Specialised cells


  Eukaryotic cells that become specialised for specific functions in complex multicellular organisms
• Specialised eukaryotic cells


  • Have specific adaptations to help them carry out their functions
  • The structure of a cell is adapted to help it carry out its function
• Structural adaptations of specialised cells

  • The shape of the cell
  • The organelles the cell contains (or doesn't contain)
• Cells adapted for protein production

  • Contain many ribosomes (the organelle responsible for protein production)
• Erythrocytes (Red blood cells)

  • Biconcave shape increases surface area available for oxygen absorption
  • Function: transport oxygen around the body and carbon dioxide to the lungs
• Neutrophils


  • Biconcave shape increases surface area for oxygen absorption
  • Cytoplasm contains high amounts of haemoglobin to bind oxygen
  • No nucleus to make more space for haemoglobin
  • Elastic membrane allows flexibility to squeeze through narrow capillaries
• Neutrophil function


  Destroy pathogens by phagocytosis and secretion of enzymes
• Neutrophil adaptations


  • Very flexible shape to squeeze through cell junctions
  • Form pseudopodia to engulf microorganisms
  • Large number of lysosomes to digest invading cells
  • Flexible nuclear membrane to penetrate cell junctions
• Sperm cells


  • Head contains haploid nucleus
  • Acrosome contains enzymes to break down egg cell
  • Mid-piece packed with mitochondria for energy
  • Tail rotates to propel cell forward
• Sperm cell function


  Fuse with egg, initiate embryo development, pass on father's genes
• Root hair cells


  • Extension of cytoplasm to increase surface area for water and mineral absorption
  • Thin walls for easy water movement
  • Permanent vacuole maintains water potential gradient
  • Mitochondria for active ion transport
• Root hair cell function

  Absorption of water and mineral ions from soil
• Ciliated epithelium


  • Cilia beat in coordinated way to move substances across surface
  • Goblet cells secrete mucus to trap dirt and microbes
• Ciliated epithelium function


  Moving substances across the surface of a tissue
• Squamous epithelium


  • Single layer of flattened cells on a basement membrane
  • Thin cross-section reduces diffusion distance
  • Permeable to allow easy gas diffusion
• Squamous epithelium function


  Provide a surface covering or outer layer
• Palisade cells


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• Fad and thin palisade cells

  • Densely packed together
  • For the maximum absorption of light
• Guard cells


  • A large number of chloroplasts (the site of photosynthesis) are present in the cytoplasm to maximise the absorption of light for photosynthesis
  • The tail and thin shape of the cells allows light to penetrate deeper before encountering another cell wall (cell walls absorb/reflect light) and for many cells to be densely packed together
• Guard cells are turgid


  Stoma is open
• Guard cells are flaccid


  Stoma is closed
• Cell walls


  • Inner cell walls are thicker (those facing the air outside the leaf) while the outer cell walls are thinner (those facing adjacent epidermal cells)
  • The difference in the thickness of the cell walls allows the cell to bend when turgid
• The cytoplasm has a high density of chloroplasts and mitochondria
• Scientists think that these organelles may play a role in the opening of the stomata