B1

• Cell Differentiation


  The process by which a cell changes to become specialised for its job
• Differentiated cells


  • They have different subcellular structures to suit their different functions
  • They can carry out specific functions
• Cell differentiation


  1. Occurs as an organism develops

  2. In most cell types, the ability to differentiate is lost at an early stage, after they become specialised

  3. However, lots of plant cells don't ever lose this ability
• Undifferentiated cells


  Stem cells
• Sperm cells


  • Specialised for reproduction
  • Have a long tail and streamlined head to help reach the egg
  • Have many mitochondria to provide energy
  • Carry enzymes in the head to digest through the egg cell membrane
• Nerve cells


  • Specialised for rapid signalling
  • Are long to cover more distance
  • Have branched connections at their ends to connect to other nerve cells and form a network
• Muscle cells


  • Specialised for contraction
  • Are long to have space to contract
  • Contain many mitochondria to generate the energy needed for contraction
• Root hair cells


  • Specialised for absorbing water and minerals
  • Grow into long "hairs" that stick out in the soil to increase surface area for absorption
• Phloem and xylem cells


  • Specialised for transporting substances
  • Form tubes by being long and joined end to end
  • Xylem cells are hollow in the centre and phloem cells have very few subcellular structures to allow flow of substances
• Most cells have the same genes, but they differentiate to become specialised
• Chromosomes control the genes that determine the structure and function of a cell
• Body cells have the same genes as the original cell they came from
• Plants transport food substances in phloem and water in xylem