topic 3 - infection and responce

• Microorganisms


  A group of tiny organisms including bacteria, viruses, protists and fungi
• Pathogens


  Microorganisms that can cause disease
• Communicable/infectious diseases


  Diseases caused by pathogens that can spread from person to person
• Types of pathogens


  • Bacteria
  • Viruses
  • Protists
  • Fungi
• How pathogens spread


  1. Through the air

  2. Through contaminated food and water

  3. Through direct contact
• Pathogens spread through the air

  Carried in tiny droplets expelled when coughing or sneezing
• Pathogens spread through contaminated food and water


  Example: Cholera is spread by drinking contaminated water, Salmonella is spread by eating contaminated food
• Ways to reduce pathogen spread

  • Being hygienic (washing hands, cleaning cooking items)
  • Killing vectors (using insecticides)
  • Vaccinating people
  • Quarantining infected people
• Preventing disease spread is better than treating it
• Viruses


  • Not cells, not living, but considered organisms
  • About 10,000 times smaller than animal cells
  • Can't reproduce by themselves, but can use a host cell's machinery to make copies of themselves
  • Can burst the host cell to release new viruses to infect other cells
• Viruses colonizing and bursting host cells

  Damages the body and makes us feel ill
• Viral diseases covered


  • Measles
  • HIV
  • Tobacco mosaic virus
• Measles virus


  • Spread by droplets when an infected person coughs or sneezes
  • Causes a red rash and fever
  • Rare in UK due to vaccination
• HIV


  • Human Immunodeficiency Virus
  • Spreads through sexual contact or sharing bodily fluids
  • Causes a deficient immune system
  • Initially causes flu-like symptoms, then weakens the immune system over time
  • Can develop into AIDS if left untreated
  • Treatable with antiretroviral drugs
• Tobacco mosaic virus (TMV)


  • Affects certain plant species like tobacco and tomato
  • Discolours patches on leaves, disrupting photosynthesis and plant growth
• Most bacteria don't have anything to do with humans, and the ones that do actually help us
• Bacteria


  Single-celled organisms about 100 times smaller than our own cells
• Bacteria can replicate rapidly within our bodies because of the good food supply
• Bacteria


  They might produce toxins which make us feel ill by damaging our cells and tissues
• Bacterial disease


  • Salmonella
• Salmonella causes food poisoning and we can catch it from any food that has been contaminated with the bacteria, most often by eating chicken that caught the disease
• In the UK, most chickens have to be vaccinated against salmonella, so it's relatively rare
• Symptoms of salmonella


  • Fever
  • Stomach cramps
  • Vomiting
  • Diarrhea
• Salmonella generally passes by itself within a week, and people just need to stay well hydrated and have a sick bowl close by
• Bacterial disease


  • Gonorrhea
• Gonorrhea


  A sexually transmitted disease (STD) passed on through sexual contact, for example having unprotected sex
• Symptoms of gonorrhea


  • Pain when urinating
  • Thick yellow-green discharge from the vagina or penis
• We used to use a common antibiotic penicillin to treat gonorrhea, but now a lot of gonorrhea strains are resistant to penicillin, so we're using rarer and more expensive antibiotics
• The best prevention for gonorrhea is avoiding unsafe sex and using barrier methods of contraception like condoms
• Fungi


  Eukaryotic organisms, can be unicellular or multicellular
• Fungi


  • Yeast (unicellular)
  • Mushrooms (multicellular)
• Fungi


  • Have long thread-like structures called hyphae which come out of the main body and spread through the soil
  • Hyphae can spread over plants or even penetrate human skin and cause disease
  • Hyphae can produce spores which spread easily and grow into new fungi
• Fungal disease


  • Rose black spot
• Rose black spot


  • Causes purple or black spots to form on the leaves of plants, especially roses
  • As the fungus does more damage, the leaves can start to turn yellow and drop off
• Treating rose black spot

  1. Chop off all infected leaves and destroy them

  2. Spray the plant with fungicides which kill any fungus
• Protists


  • Eukaryotic organisms, can be single-celled or multi-celled
  • Majority are single-celled or unicellular
  • Some are classified as parasites, living on or inside other organisms and surviving at that organism's expense
• Vectors


  Other organisms like insects that transport protists between different host organisms, but the vectors don't get the disease themselves
• Protist disease


  • Malaria
• How malaria spreads


  1. Mosquito feeds on infected animal and sucks up malaria parasites

  2. Mosquito then feeds on healthy person, transferring the parasites
• Malaria symptoms


  • Recurrent episodes of bad fevers, headaches, and feeling dreadful
  • Can be fatal in some cases