Topic 3 - B3

• What is a pathogen?


  A microorganism that enters the body and causes disease
• What are bacteria?


  Very small cells (about 1/100 the size of your body cell) which reproduce rapidly inside your body, they make you feel ill by producing toxins that damage cells and tissues
• What is a virus?


  About 1/100 the size of bacterium, reproduce rapidly inside your body, live inside your cells and replicate themselves making many copies of themselves, the cell will usually then burst releasing all the new viruses this cell damage is what makes you feel ill
• What is a protists?


  All are eukaryotic cells but only some are parasites that live on or inside other organisms and cause damage
• What is a fungi?


  Made up of hyphae (thread light structures) they can grow and penetrate human skin and the surface of plants causing disease they can also produce spores which can spread to other plants and animals
• Measles:

  • a viral disease
  • spread from dropets (cough or sneeze)
  • symptoms: red rash and fever
  • can lead to pneumonia or inflammation of the brain
  • vaccinated against when young
• HIV:

  • viral disease spread by sexual contact or exchanging bodily fluids
  • symptoms: can take years to show but include flu like symptoms
  • controlled with antiretrovrial drugs which stop virus replicating
  • attacks immune system and damages it
  • when system becomes badly damaged its called AIDs
• Tabacco mosaic virus (TMV):

  • virus that affects plants
  • mosaic pattern on leaves causes discolouration
  • this discolouration means plant can't carry out photosynthesis so it can't grow
• Rose black spot:

  • fungal disease
  • causes purple or black spots to appear on rose leaves
  • the leaves then turn yellow and fall off
  • this means less photosynthesis and stunt of growth
  • you can treat this disease by pulling affected leaves and destroying them so it doesn't spread
• Malaria:

  • cause by a protist
  • the mosquito is the vector (organism which doesn't get the disease) picks up disease from infected animal
  • every animal that is feed on by mosquito is infected by the protist entering bloodstream
  • causes episodes of fever and can be fatal
  • can be protected by insecticides, nets and stopping mosquitoes breeding
• Salmonella

  • bacteria which causes food poisoning
  • symptoms: fever, stomach cramps, vomiting and diarrhoea
  • caused by toxins that bacteria produce
  • poultry is vaccinated against salmonella
• Gonorrhoea:

  • sexually transmitted disease
  • cause by bacteria
  • symptoms: pain when urinating and thick yellow discharge
  • use to be treated with antibiotic penicillin but it's now resistant
  • some people can be treated with antibiotics and should use barrier methods of contraception
• Defence system:

  • skin

  -> barrier to pathogens and secretes antimicrobial substances which kill pathogens

  • hair and mucus

  -> traps particles that could contain pathogens

  • trachea and bronchi

  -> secrete mucus to trap pathogens

  • cilia (in trachea and bronchi)

  -> waft mucus up the back of throat to be swallowed

  • hydrochloric acid

  -> kills pathogens
• How does the immune system attack pathogens?

  (1) white blood cells engulf cells and digest them this is called phagocytosis

  (2) pathogens each have unique antigens on the surface

  (3) when encountering foreign antigen they produce proteins called antibodies to lock onto invading cell so can be found and destroyed by other white blood cells

  (4) antibodies are produced rapidly and carried around body to find all similar bacteria or viruses

  (5) white blood cells produce antitoxins to counteract toxins produced by invading bacteria
• Where does aspirin come from?


  Willow
• Where does digitalis come from?


  foxgloves
• Where does penicillin come from?


  Mould
• Monoclonal Antibodies:

  1. antibodies are produced by B-lymphocytes (type of white blood cell)
  2. monoclonal anitbodies means lots of clones of identical antibodies which target on antigens
• How to make monoclonal antibodies:

  1. mouse gets injected with chosen antigen
  2. fast-dividing tumour cells are taken from lab
  3. B-lymphocytes taken from mouse
  4. tumour cell fused with B-lymphocyte
  5. both put together to make a hybridoma
  6. it divides quickly to produce monoclonal antibodies
• What does nitrate ions do in plants?


  make proteins to help grow
• What happens if a plant has a lack of nitate ions?


  Has stunted growth
• What do magnesium ions do in plants?


  make chlorophyll which is needed ti absorb light for photosynthesis
• What happens if a plant has a lack of magnesium ions?


  has yellow leaves and can't do photosynthesis
• Monoclonal antibodies in pregnancy test:

  1. the bit of the stick you wee on has antibodies to the hormone with blue beads attached
  2. the test strip (goes blue when pregnant) has more antibodies that get stuck to hormone
  3. if your pregnant: hormone binds to antibodies on blue beads and urine moves up stick carrying hormone beads which then bind to antibodies on strip becoming stuck and turning blue
  4. if not pregnant: urine moves up stick carrying blue beads but no hormone to bind to antibodies so doesn't turn blue