Exchange and Transport in Animals

• Blood plasma


  The liquid part of the blood
• Functions of blood plasma

  1. Transports dissolved substances around the body

  2. Transports soluble digestion products from small intestine to other organs

  3. Transports carbon dioxide from body cells to lungs to be breathed out

  4. Transports waste product urea from liver to kidneys to be excreted
• Red blood cells


  • Contain the oxygen-carrying molecule hemoglobin
  • Have no nucleus, allowing more space for hemoglobin
  • Have a biconcave disk shape, giving greater surface area for oxygen diffusion
• Function of red blood cells

  Transport oxygen from lungs to body cells
• White blood cells


  • Contain a nucleus with DNA encoding instructions
  • Part of the immune system, e.g. making antibodies
• Platelets


  Tiny fragments of cells that help the blood to clot
• Uses of donated blood

  • Replace blood loss during injury
  • Platelets extracted to help in clotting
  • Proteins extracted, e.g. antibodies
• Blood transfusion


  Donated blood must be the same blood type as the patient, otherwise the body's immune system will reject it and the patient could die
• Using blood products


  Risk of transmitting infections
• In the UK, blood is screened for infection, so the risk is extremely low