Infection and Response

• What is a pathogen?

  a microorganism that causes infection or diseases
• what are the four types of pathogen?


  protists, fungi, bacteria and viruses
• What is bacteria?


  Bacteria are very small cells that can reproduce very quickly in your body and in the right conditions - produce antitoxins that damage your cells and tissues
• What are viruses?

  • not cells - they are much smaller and reproduce rapidly inside your body
  • live inside your cells and replicate themselves using the cells' machinery until your cells burst - this is what makes you feel ill
• What are protists?

  • single-celled eukaryotes
  • some are parasites which live on or in other organisms and cause them damage
  • often transferred by a vector which isn't effected by the disease
• What is fungi?

  • some are single-celled
  • others have a body made up of hyphae which grows and penetrates human skin and the surface of plants which causes disease
• How are pathogens spread?

  • Water
  • air
  • direct contact
• What is measles?*

  • a viral disease spread by droplets from an infected person's sneeze or cough
  • develop a red skin rash and fever
  • can be very serious if there are complications - can lead to pneumonia or an inflammation of the brain
  • most people are vaccinated when they are young
• What is HIV?*

  • a virus spread by sexual contact or by exchanging bodily fluids such as blood (sharing needles when taking drugs for example)
  • initially causes flu-like symptoms for a few weeks in which it can be controlled by antiretroviral drugs to stop it replicating
  • virus attacks the immune cells
  • if the bodies immune system is badly damaged it can't cope with other the infections or cancers and then it is classed as AIDS or late stage HIV
• What is tobacco mosaic virus?*

  • a virus that effects many species of plant
  • causes a mosaic pattern on the leaves and parts of leaf become discoloured
  • the discolouration means the plant can't carry out photosynthesis therefore affecting the plants growth
• What is rose black spot?*

  • a fungus that causes purple or black spots to develop on the leaves of rose plants - leaves can then turn yellow and drop off
  • leads to less photosynthesis so growth is stunted
  • spreads through water and the wind in the environment
  • treat with fungicides and by stripping the plant of any diseased leaves
• What is malaria?*

  • caused by a protist
  • takes place inside of a mosquito (vectors) which, when they feed on another animal, inserts the protist into the animals blood vessels
  • causes repeating episodes of fever - can be fatal
  • can be stopped by stopping the breeding of mosquitoes
  • people can be protected from mosquitoes by using mosquito nets and insecticides
• What is salmonella?*

  • a type of bacteria that causes food poisoning - fever, stomach cramps, vomiting and diarrhoea
  • caused by the toxins produced by the bacteria
  • can get it from eating contaminated foods - chicken that caught the disease while being alive, unhygienic conditions
  • most poultry in UK is vaccinated against salmonella
• What is Gonorrhoea?*

  • a STD - passed on by sexual contact
  • will get pain when they urinate, thick yellow or green discharge
  • originally treated by antibiotics but the strain of bacteria has become resistant
  • should use barrier methods (condoms) to prevent spread
• How is the spread of disease reduced?

  • being hygienic - washing your hands after and before cooking and if sick etc.
  • destroying vectors - getting rid of organisms that can spread disease e.g. insect nests destroyed to stop them from breeding
  • isolating infected individuals - prevents it passing on to other people
  • vaccination - can't develop the infection and then pass it on to someone else
• How does the body defend from pathogens?

  • skin - acts as a barrier to pathogens and also secretes antimicrobial substances to kill pathogens
  • hairs and mucus - trap particles that could contain pathogens
  • trachea and bronchi - secretes mucus to trap pathogens and are lined with cilia which waft the mucus to the back of the throat to be swallowed
  • stomach produces hydrochloric acid which kills pathogens
• How do phagocytes attack pathogens?

  engulf and digest them
• how do lympocytes attack pathogens?

  • invading pathogens have a specific shaped antigens on its surface
  • when they come across the pathogen they produce antibodies to lock onto the invading cell so they can e found and destroyed by other white blood cells