Key points

• Osmosis is diffusion of water from a dilute to a more concentrated solution
• Respiration releases energy for active transport
• Diffusion does not require energy
• Use of stem cells issues

  Ethical =potential life destroyed by using embryos

  Other = transfer of viral infection

  Risk of rejection by immune system

  need to take immunosuppressant drugs after treatment
• Mitosis creates new cells to replace the damaged or dead ones therefore repairing the tissue but not the cells themselves
• DNA replicates before mitosis so that the new cells that have formed can have the same number of chromosomes as the original cell