Infection and Response

• a pathogen is a microorganism that causes disease
• Bacteria -

  • very small living cells
  • can reproduce rapidly
  • produce toxins that damage your cells and tissues, which make you feel ill
• Viruses -

  • not cells, smaller than a bacterium
  • reproduce rapidly
  • live inside cells and replicate rapidly
  • cells burst and release new viruses, the cell damage makes you feel ill
• Protists -

  • single celled Eukaryotes
  • some are parasites, and live on or inside an organism and cause damage
  • often transferred by a vector
• Fungi -

  • some are single celled, others have a body made up of Hyphae
  • can grow and penetrate human skin and plants, causing diseases
• some pathogens can be picked up by drinking or bathing in dirty water, for example Cholera
• pathogens can be carried in the air and can then be breathed in, for example the Influenza virus
• some pathogens can be picked up by touching contaminated surfaces, including the skin, for example Athlete's foot
• Measles -

  • virus
• Measles -

  • virus
  • spread by droplets
  • infected people can develop a red skin rash and a fever
  • can be vaccinated against it
• HIV -

  • Virus
  • spread by sexual contact or sharing needles
  • presents with flu like symptoms
  • can be controlled with antiretrovial drugs
  • the immune system is badly damaged, and can't cope with other infections - this is known as AIDS
• Tobacco Mosaic Virus (TMV) -

  • virus
  • causes a mosaic pattern on leaves, parts of leaves become discoloured
  • plant can't carry out photosynthesis so this affects growth
• Rose Black Spot -

  • Fungi
  • purple or black spots to develop on leaves of rose plants
  • less photosynthesis can happen, stunting growth
  • spreads through water or wind
  • can be treated by stripping and destroying affected leaves
• Malaria -

  • Protist
  • transmitted by mosquitos - which are vectors, they infect by inserting the protist into blood vessels
  • causes repeating episodes of fevers - and can be fatal
  • can get vaccinated, or to protect from mosquitos - use mosquito nets or insecticides
• Salmonella -

  • bacteria
  • people can suffer from fever, stomach cramps, vomiting and diarrhoea
  • caused by toxins from uncooked food or by chicken that has been contaminated while alive and not been prepared hygienically
• Gonorrhoea -

  • bacteria
  • transmitted via sexual contact
  • symptoms are - pain white urinating, yellow or green discharge from penis or vagina
  • can be treated with antibiotics, but people should use barrier methods - such as condoms
• the body's defence system -

  • skin
  • hair
  • mucus
  • trachea and bronchi
  • stomach
• the skin acts as a barrier to pathogens
• hairs and mucus in your nose trap particles that could contain pathogens
• the trachea and bronchi secrete mucus to trap pathogens
• the trachea and bronchi are lined with cillia, which waft the mucus up the back of your throat so it can be swallowed
• the stomach produces HydroChloric acid which kills bacteria that make it far from mouth
• white blood cells can engulf foreign cells and digest them in a process called Phagocytosis
• vaccinations involve injecting small amounts of dead or inactive pathogens, these carry antigens, which cause your body to produce antibodies to attack them - even though they are harmless
• benefits of vaccinations -

  • control lots of communicable diseases that were once common - for example Polio
  • big outbreaks of disease - called epidemics - can be prevented if a large population is vaccinated
• drawbacks of vaccinations -

  • sometimes they do not give you immunity
  • can sometimes have a bad reaction, but they are very rare
• painkillers are drugs that relieve pain, however they don't actually tackle the cause of disease or kill the pathogen
• antibiotics (for example Penicillin) actually kill, or prevent the growth, of bacteria causing the problem without killing your bodies cells
• bacteria can mutate and become resistant to antibiotics. when you have an infection and take antibiotics, only the non-resistant bacteria will be killed, which leaves the stronger and less resistant bacteria to survive and continue to reproduce