Specialised Cells

• What are Specialised cells?

  Specialised cells have features that enable them to carry out their specific function. 
• Erythrocytes

  • Flattened biconcave shape - This increases the surface area to volume ratio to allow diffusion of oxygen. 
  • No nucleus or organelles - This provides more room for haemoglobin (the molecule that binds to oxygen). 
  • Flexible  - This is so they can fit through narrow capillaries.
• Neutrophils (White Blood cells)

  Specialised features: 

  • Flexible cell membrane - This allows the cell to engulf pathogens. 
  • Contain many lysosomes - These contain digestive enzymes to break down engulfed particles.
  • Multi-lobed nucleus - This allows cells to deform so they can squeeze through small gaps to reach sites of infection. 
• Stem Cells

  Specialised features: 

  • Flagellum (tail) - This allows the cell to swim to the egg cell. 
  • Many mitochondria - These supply the energy needed for movement. 
  • Acrosome containing digestive enzymes - These digest the protective layers around the egg cell to allow the sperm cell to enter it.
• Squamous epithelial cells

  Specialised features:

  Very thin - This allows efficient diffusion of gases such as oxygen and carbon dioxide.

  
  

  Permeable - This allows diffusion of gases.
• Ciliated epithelial cells

  Ciliated epithelial cells also cover the surface of organs where they can move substances such as mucus or egg cells. They are found in organs such as the bronchioles and fallopian tubes.

  
  

  Specialised features:

  Cilia (hair-like structures) - These beat to move pathogens and mucus away from the lung or egg cells towards the uterus.
• Palisade cells

  Specialised features:

  
  

  Lots of chloroplasts - These absorb the light needed for photosynthesis.

  
  

  Thin cell walls - This allows carbon dioxide to quickly diffuse into the cell.

  
  

  Tall and thin shape - This allows many palisade cells to closely pack together to form a continuous layer near the surface of the leaf.
• Root Hair cells

  Root hair cells absorb water and mineral ions from the soil.

  Specialised features:

  
  

  Root hair structures - These increase the surface area for absorption.

  
  

  Thin, permeable cell wall - This allows entry of water and ions.

  
  

  Lots of mitochondria - These provide energy for active transport.
• Guard cells

  Specialised features: 

  • Come in pairs - This allows a gap (stoma, plural: stomata) to form between them. 
  • Change shape when light is present - Guard cells absorb water to become turgid, opening the stoma to allow entry of carbon dioxide. 
  • Change shape when they lose water - Guard cells shrink and close the stoma to prevent water loss. 
  • Thin outer walls and thick inner walls - This allows the cells to bend when they are turgid to open the stoma.