Infection and response

• Bacteria


  Very small cells that reproduce rapidly

  Make you feel ill by producing toxins that damage your cells and tissues
• Viruses 


  Aren't cells and reproduce rapidly in the body.

  They live inside cells and replicate themselves. The cell will then likely burst, releasing the new viruses

  The cell damage is what then makes you feel ill
• Protists 


  Single celled eukaryotes

  Some are parasites which live on or in other organisms and can cause them damage

  They are often transferred by a vector
• Fungi 


  Hyphae can grow and penetrate human skin and the surface of plants, causing diseases

  The hyphae can also produce spores
• Pathogens can spread through

  Water- drinking or bathing in dirty water

  Air- carried in the air and breathed in

  Direct contact- touching contaminated surfaces
• Measles (viral disease)


  Spread by droplets from sneezes or coughs

  Symptoms like red skin rash, and fevers

  Vaccinations are available
• HIV (viral disease)


  Spread through sexual contact or exchanging bodily fluids

  Causes flu-like symptoms and attacks the immune cells

  Controlled by antiretroviral drugs to stop it from replicating in the body
• Tobacco Mosaic virus (TMV-viral disease)

  Affects many species of plants e.g. tomatoes

  Causes a mosaic pattern and parts of the leaves become discoloured

  This means photosynthesis cant be carried out as efficiently so the growth is affected
• Rose black spot (fungal disease)


  Causes purple and black spots to develop on the leaves. They then turn yellow and drop off.

  This means that less photosynthesis can happen so the plant doesn't grow very well.

  Spreads through wind or water

  Treated with fungicides and stripping the plant of infected leaves
• Malaria (protist disease)


  Mosquitoes are vectors which feed on the animal and insert the protist in its blood vessels

  Causes repeating episodes of fevers and can be fatal

  Can be managed by stopping the mosquitoes from breeding and people can use mosquito nets and insecticides
• Salmonella (bacterial disease)


  Causes food poisoning

  Symptoms like fever, stomach cramps, vomiting and diarrhoea

  Poultry is given a vaccination to control the spread
• Gonorrhoea (bacterial disease)


  Sexually transmitted disease caused by bacteria

  Symptoms include pain when urinating and thick yellow/green discharge

  Originally treated with the antibiotic, penicillin but it has now become resistant to it

  To reduce the spread, people can be treated with antibiotics and use barrier methods of contraception
• Reducing the spread of disease


  Being hygienic

  Destroying vectors

  Isolating infected individuals

  Vaccinations
• The skin 


  Acts as a barrier to pathogens.

  Secretes antimicrobial substances to kill pathogens
• Hairs and mucus


  Trap particles that could contain pathogens
• Trachea and bronchi 


  Secretes mucus to trap pathogens

  Lined with cilia to waft mucus to the back of the throat to be swallowed
• Immune system


  White blood cells

  1. Engulf foreign cells and digest them (phagocytosis)
  2. Producing antibodies after coming across a foreign antigen
  3. They are produced rapidly and carried around the body to find similar bacteria/virus
  4. Producing antitoxins to counteract toxins produced by invading bacteria
• Vaccination 


  Injecting a dead or inactive pathogen which carry antigens which cause the body to produce antibodies

  If live versions of the pathogen then enter the body, white blood cells will produce them rapidly
• Pros and cons of vaccinations


  Pros: Control lots of previously common communicable diseases, big outbreaks of the disease can be prevented

  Cons: Dont always work, sometimes people may have bad reactions (although rare)
• Painkillers


  Drugs that relieve pain (reduce symptoms) but don't tackle the cause of the disease or kill pathogens
• Antibiotics


  Kill (or prevent the growth of) the bacteria causing the problem without killing your own body cells

  Don't destroy viruses as they reproduce using your own body cells.