communicable diseases

• plant can defend themselves in 2 ways ; chemical or physical
• plants use receptors on surface which stimulate the release of signalling molecules that switch on genes therefore triggering a response if a pathogen is detected.
• physical defences

  • callose acts as a barrier
  • ligin for extra strength
  • callose blocks off sieve plates
  • callose is deposited in the plasmodesmata between infected cells therefore sealing them off
• chemical defences

  • insect repelent
  • insecticides
  • antibacterial compounds
  • anti fungal compounds
  • anti-oomycetes
  • general toxins
• the inflammatory response involves mast cells being activated and releasing histamines and cytokines
• histamines dilate vessels which increase the temperature and also make the walls of the vessels more leaky and allow blood plasma to be forced out and making tissue fluid which causes swelling
• cytokines attract white blood cells
• blood clot

  1. platelets release thromboplastin
  2. thromboplastin + prothrombin + calcium
  3. = thrombin
  4. thrombin + fibrinogen
  5. = fibrin which allows for the blood to clot
• thromboplastin triggers a cascade of reactions needed for the clotting of the blood
• antibodies have 3 ways of working

  • acts as opsonin making the pathogen easily engulfed
  • acts as a agglutinins which clump together the pathogens
  • acts as anti-toxins which bind to the toxins produced by the pathogen and makes them harmless
• 4 types of T lymphocytes

  1. T helper
  2. T killer
  3. T memory
  4. T regulator
• T helper cells produce interleukins ( type of cytokines) which stimulate the activity of B lymphocytes
• T killer cells destroy pathogens with antigens by producing perforin which makes holes in the cell membrane of the pathogen
• T memory cell are apart of the immunological memory and when invaded again can divide into T helper cells
• T regulator cells suppress the immune response once the pathogen has been eliminated.
• 3 main types of B lymphocytes

  1. plasma cells
  2. B effector cells
  3. B memory cells
• plasma cells produce specific antibodies and release them into circulation
• B effector cells divide into plasma cells clones
• B memory cells provide immunological memory and remember a specific antigen and enable bodies response