Specialised cells

• Specialised cells are cells designed to carry out a specific function
• Nerve cells carry electrical impulses around the body and are found in the brain and spinal cord
• Nerve Cell adaptations

  Has a cell body where most cellular structures are located and protein synthesis occurs
• Nerve cell adaptations 


  Extensions of the cytoplasm from the cell body form dendrites( which receive signals) and axons( which transmit signals) allowing the neurone to communicate with other nerve cells, muscles and glands
• Nerve cells adaptations

  The axon is covered with a fatty sheath which speeds up nerve impulses
• Muscles cells contain layers of fibres which allow them to contract
• The function of a muscle cell

  Contraction for movement
• Muscle cell adaptations 


  Have layers of protein filaments. These layers can slide over each other causing muscle contraction
• Muscle cell adaptation 


  Have a high density of mitochondria to provide energy for muscle contraction
• Function of sperm cell

  Fertilise egg cell
• Adaptation of sperm cell

  The mid-piece is packed with mitochondria to release energy for the tail
• Adaptations of sperm cell

  The tail rotates allowing it to swim
• The acrosome located in the head contains digestive enzymes that can break the outer layer of an egg cell so that the haploid nucleus can enter to fuse with the egg’s nucleus
• The function of the root hair cell is to absorb water and mineral ions from the soil
• Adaptations if root hair cell

  Increases the surface area so the rate of water uptake by osmosis and absorption of ions is greater
• Chloroplasts are not found in root hair cell as there is no light underground
• Adaptations of root hair cell

  Thinner walls so that water can move through easily due to the shorter diffusion distance
• Adaptations of root hair cell

  Mitochondria for active transport of mineral ions
• xylem cell function 


  Transports water and dissolved ions from the roots to the stem and leaves
• Adaptation of xylem 


  No top and bottom walls between cells to form continuous hollow tubes through which water is drawn up to the leaves by transpiration

  
• adaptations of xylem


  Cells are essentially dead, without organelles or cytoplasm , to allow free passage of water
• adaptations of xylem 


  Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant
• phloem cells form tubes similar to xylem vessels, except the cells still retain some sub- cellular structures and are therefore living
• Function of phloem cells

  Transport dissolved sugars and amino acids up and down the plant, that have been produced by photosynthesis
• Adaptations of phloem


  Made from living cells( as opposed to xylem cells that are made from dead cells) which are supported by companion cells

  
• Adaptations of phloem


  Cells are joined end to end and contain holes in the end cell walls ( sieve plates) forming tubes which allow sugars and amino acids to flow easily by translocation
• adaptations phloem


  Cells have few sub cellular structures to aid the flow of materials