Infection and response

• what are microorganisms 


  a group of tiny organisms including bacteria, viruses, protists and fungi
• What are pathogens 


  Microorganisms that can cause disease
• what are communicable diseases and diseases what they affect 


  when pathogens spread to person to person the disease they cause are known as communicable diseases-these Effect both animals and plants
• How do pathogens spread 


  air

  contaminated food and water

  direct contact
• How are pathogens spread through air 


  Many air born pathogens e.g. influenza virus or measles virus are carried in tiny droplets that we expel when we cough or sneeze
• How pathogens spread through Contaminated food and water 


  e.g. Cholera which is a bacterial disease, is spread by drinking water contaminated by the diarrhoea of somebody that’s suffering from cholera

  e.g. salmonella bacteria is spread by eating contaminated food,particularly chicken
• How pathogens spread through direct contact 


  e.g. athletes foot which is a fungal infection which can make skin on your feet flake off which is spread by walking barefoot on contaminated surfaces e.g. public swimming pools
• How to stop pathogens spreading

  1. Hygiene - washing hands, cleaning cookery items e.g. Knives

  2. Kill the vectors (organisms that transport the pathogen) e.g. Mosquitos which transport the malaria protists - To kill insect vectors, spread insecticides which are chemicals that kill insects

  3. Vaccinate everybody because if people can't catch the disease then they can't pass it on

  4. If all of these methods fail and somebody catches the disease then they will Isolate or Quarantine - only if it is a really serious disease that can harm others if they get infected so No contact with anyone
• Information on viruses 


  not cells but not living-consider as organisms

  they are 10,000x smaller then animal cells and can’t reproduce by themselves
• what do viruses do 


  Once they get inside another organism, they use that cells own machinery to make loads of copies of themselves and when the time is right they can burst the cell, all those new viruses will then have to find new cells to take over

  This process of colonising and then bursting our cells is going to damage our bodies-main reasons viruses make us feel ill
• measles (caused by a virus)


  Spread by droplets when an infected person coughs or sneezes which causes people to develop a red rash across their body and a fever(high temperature)

  can be really Fatal but is luckily really rare in the UK as everyone is vaccinated against it when there young
• HIV


  Human immune deficiency virus, a virus that affects humans with an inadequate immune system
• HIV


  • Classed as a virus
  • Spread by sexual contact e.g. unprotected sex or exchanging bodily fluids e.g. blood when people share needles
• Progression of HIV infection


  1. When first caught, many get flu-like symptoms for a few weeks e.g. fever, tiredness and aches (then they will start to feel better)

  2. Viruses do more and more damage to their immune system

  3. Immune system becomes so weak they catch unusual infections which sometimes can be cancers

  4. At this point they have developed AIDS in which the person's immune system can't cope
• Antiretroviral drugs


  Medication that prevents viruses from replicating within our bodies, allowing people with HIV to live a normal life if they have access to it early in their disease
• Tobacco mosaic virus (virus)


  infects plants instead but only certain species such as tobacco and tomato plants,it discolours patches on the leaves causing a mosaic pattern to form

  PROBLEM:photosynthesis can’t take place in these discoloured patches and so the plant cant produce sugars for GROWTH
• what do bacteria have to do with humans 


  Most bacteria don’t have anything to do with humans and most of the ones that do actually help us
• What are bacteria 


  Single-celled organisms and 100x smaller than our own cells
• what do bacteria do 


  they can reproduce by themselves, they often replicate rapidly within our bodies because of the good food supply, at the same time they might produce toxins which make us feel ill by damaging our cells and tissues
• salmonella(bad bacteria diseases)


  causes food poisoning, can catch it and it’s any food that has been contaminated from the bacteria ,but most often is by eating chicken that caught the disease when it was alive

  In the UK most chickens have been vaccinated against salmonella so it is relatively rare

  if u do catch it you are likely to get fever, stomach cramps, vomiting and diarrhoea

  It infects your intestines which this can pass by itself in a week if you stay well hydrated
• Gonorrhea(bad bacteria disease)


  •An example of an STD which is passed on through sexual contact e.g. unprotected sex

  main symptoms are pain when urinating and a thick yellow/green discharge from the vagina and penis

  •Prevent it: avoiding unsafe sex, barrier methods of contraception e.g. Condoms

  •treatment:used to use penicillin which was cured with now issues however now lots of gonorrhea strains have become resistant to penicillin so we are using rarer and more expensive antibiotics
• What is fungi 


  Organisms like plants and animals but unlike plants and animals fungi can be unicellular or multicellular E.G yeast is a unicellular fungi which is used to make bread rise E.G mushrooms are multicellular fungi

  often multicellular ones have long thread like structures called HYPHAE which come out of the main body and spread through the soil occasionally HYPHAE spread over plants or even penetrate human skin and caused disease. The HYPHAE can also produce SPORES which spread easily and grow into new fungi.
• Fungal disease


  Rose black spot causes purple or black spots on the leaves of plants especially roses. As the fungus does more damage the leaves start to turn yellow and drop off which reduces the ability to photosynthesise and so they don’t grow as well. This spreads in the water or by the wind, treatment is to chop off infected leaves or spray with fungicide which kill any fungus, if you chop off the leaves make sure to destroy them so the fungi can’t spread to any other plant
• what are protists 


  They are eukaryotes and can be the single or multicellular organisms however the large majority of them are single celled. Some of them are classed as parasites which live on or inside another organism and survive at other organisms expense. they are often transported by vectors which are other organisms like insects that transport the protists between different host organisms. Vectors don’t get the disease themselves
• Protist disease


  Malaria is caused by parasitic protists which means it needs a host E.G human or other animals to survive. It is transported between hosts like mosquitoes. It works when a mosquitoes feeds on an animal that’s already been infected and it sucks out some blood, can also suck up the malaria parasites. Then when a healthy animal like a person comes along the mosquito feeds on that animal, the parasites get transferred at which point we would say the protists spread to a new host
• how to prevent these protists e.g malaria


  Stop the VECTORS spreading the protists for example reduce the number of mosquitoes by destroying their breeding sites or killing them with insecticides or stop them from feeding on us by using mosquito nets for mosquito repellents
• symptoms of malaria 


  Really bad fevers and headaches which go away and come back known as recurrent episodes and in some places they can be fatal
• Our defence system against pathogens


  Physical and chemical barriers-stop pathogens GETTING IN

  Immune system-DESTROY pathogens in the body
• Skin as a barrier against pathogens 


  most of our body is covered in skin which is a physical barrier that the pathogens can’t get through.It also secretes oil and antimicrobial substances which can kill the pathogens that rest on it so they can’t get through our skin so they try the nose or the mouth
• Nose as a barrier against pathogens 


  our nose has lots of little hairs and mucus which can trap pathogens and other particles as they tried to fly through in the air
• Mouth as a barrier against pathogens

  If they go through our mouth, they have to go through the oesophagus in our throat. If they go for the lungs via the trachea the trachea,bronchi,bronchioles are all covered in a layer of mucus which will trap any particles. To prevent the mucus from building up they are lined with Cilia , which move the mucus slowly up to the back of the throat where we can swallow it down to the stomach.
• stomach as a barrier against pathogens 


  We have pathogen built mucus in our stomach along with pathogens from our breakfast, luckily our stomach produces hydrochloric acid which is a strong acid which brings the pH of the stomach contents down to 2 which is so acidic that it kills all the pathogens although some may still make it into our bodies which are immune system then takes over
• when does our immune system take over


  our Immune system takes over if the pathogens are still able to enter our body
• What is the most important part of our immune system 


  our white blood cells which continually patrol the body, circulating our blood in tissues
• White blood cells


  • Phagocytosis - Engulf pathogens
  • Produce antitoxins - Bind and counteract toxins
  • Produce antibodies - Lock onto foreign antigens and signal white blood cells to destroy them
• Phagocytosis


  1. Track down pathogens

  2. Bind to pathogens

  3. Engulf pathogens

  4. Destroy pathogens
• Antitoxins


  Small molecules produced by white blood cells that can bind and counteract toxins produced by pathogens
• Antibodies


  Small proteins made by white blood cells that can lock onto foreign antigens and signal white blood cells to come destroy them
• What are each of our antibodies specific for 


  Each of our antibodies is specific for a particular antigen once our immune system knows which of our antibodies can bind the pathogens it starts producing loads of them so if we are attacked by that pathogen in the future then our body will produce loads of antibodies so quickly that it will destroy the pathogens before they can develop so they are immune to the disease
• when do we get immunity 


  Once our immune systems have been exposed to a certain pathogen they develop immunity to that pathogen and any of the diseases it causes and once we immune it means we can’t catch disease anymore E.G only catch chickenpox once although we still have to catch the disease that first time,

  which can range from unpleasant to lethal