biolgy paper 1

• Cell


  Cells all look the same. They have different structures to carry out their different functions
• Specialised Cells


  Cells that Carry Out a Specific Function
• Differentiation


  The process by which cells change to become specialised
• Differentiation


  • Cells develop different subcellular structures
  • Cells transmit information between different types of cells
  • Allows cells to carry out specific functions
• Differentiation mainly occurs as an organism develops
• Most animal cells can only differentiate at an early stage of the animal's life
• Many plant cells can differentiate for the whole of the plant's life
• The cells that differentiate in adult animals are mainly used for repairing and replacing cells
• Undifferentiated cells


  Stem cells
• There's more about undifferentiated cells on page 16
• Examples of Specialised Cells

  • Sperm cells
  • Nerve cells
  • Muscle cells
  • Root hair cells
  • Phloem cells
  • Xylem cells
• Sperm cell


  • Has a tail to help it swim to the egg
  • Has a lot of mitochondria to provide energy for swimming
• Nerve cell


  • Is long to cover more distance in the body
  • Has branches at the end to connect to other nerve cells
• Muscle cell


  • Is long so it has space to contract
  • Has lots of mitochondria to provide energy for contracting
• Root hair cell


  • Grows into long "hairs" that stick out into the soil
  • Gives the plant a big surface area for absorbing water and mineral ions from the soil
• Phloem and xylem cells

  • Form phloem and xylem tubes
  • Cells are long and joined end to end
  • Xylem cells are hollow and phloem cells have very few subcellular structures to provide space for stuff to flow through them
• Mitosis is the process of cell division
• Tadpoles and tent pegs - cells are masters of disguise
• You need to know how the cells on this page are specialised to carry out their functions