Disease causing microbe
Name the 4 types of microbe
What are the 3 natural barriers your body has to pathogens?
- Skin: the platelets help blood clot quickly to seal wounds and cuts
- Hairs and mucus in the respiratory tract trap pathogens which are swallowed into gut
- Stomach acid
Describe 3 ways white blood cells protect against pathogens.
- Ingesting them
- Producing antitoxins which counteract the toxins produced by bacteria
- Producing antibodies
How does immunity develop?
- When white blood cells come across a foreign antigen, they produce specific antibodies that lock onto a specific one
- They are produced rapidly and carried around the body
- Once white blood cells have recognised which type to produce they can do so much faster without you feeling so many symptoms
How do bacteria make us feel ill?
- Damaging cells
- Producing toxins
How do viruses make us feel ill?
- They replicate themselves by invading cells and using them to reproduce
- The cell then bursts, releasing new viruses
- This cell damage makes you feel ill
How are microbes grown in the lab?
- Sterilise the Petri Dish and nutrient agar for use by heating it in the autoclave.
- Sterilise the inoculation loop by passing it through a flame and then allowing to cool.
- Dip the sterilised loop in the microbe suspension and make zigzag streaks across the agar surface (to get an even spread of microbes across the surface)
- Close the lid as quickly as possible and seal with adhesive tape. (prevents contamination from air)
- Incubate the dishes at 25C degrees to allow microbes to grow
- After observation, resterilise the dishes complete with their cultures by heating to 100 degrees, then throw away.
How did Semmelweis change the behavior of doctors?
- He saw many women were dying from puerperal fever
- He believed doctors were spreading the disease through unwashed hands from cutting up corpses to delivering babies
- Whilst he was at hospital, he made the doctors there use antiseptics and deaths decreased.
- But his methods were dropped once he left hospital, so deaths increased
What is the process of vaccination?
- Doctor’s inject a weakened/dead microbe into your body
- White blood cells identify and make antibodies in reaction to the foreign antigen. These antibodies remain in the blood (as if the person had the disease before)
- If the real microbes attack, the body can rapidly mass-produce some antibodies to kill them off
- Some “wear off” overtime, needing booster vaccines
How do strains of bacteria become resistant?
1) Bacteria can genetically mutate, some mutations cause them to become resistant to antibiotics
2) So in treating an infection, only the non-resistant strains are killed
3) The resistant bacteria will survive and reproduce and the population of the resistant strain will increase, meaning more bacteria are untreatable by antibiotics
Give an example of a bacteria resistant to antibiotics
What’s the difference between painkillers and antibiotics?
Painkillers help to relieve the pain of symptoms, whereas antibiotics kill the pathogens.
Give one example of an antibiotic and who invented it.
Penicillin - Alexander Fleming
What reduces the spread of the pathogen across a population?
If a large proportion of the population is immune to a pathogen so that even those unvaccinated are less likely to pick up the disease because there are fewer to pass it on.
Why are antibiotics used only to kill bacteria?
It is hard to develop drugs which kill viruses without damaging body cells, as they live and reproduce inside it
A sudden outbreak of disease over a country.
A sudden outbreak of disease over the world.
How is the rate of development of resistant strains of bacteria slowed down?
Antibiotics are not used to treat non-serious infections, such as mild throat infections
What does the MMR vaccine protect against?
Why are cultures incubated at a maximum temperature of 25 °C in school/college laboratories?
It greatly reduces the likelihood of growth of
pathogens that might be harmful to humans.
Why are higher temperatures used in industrial conditions to incubate cultures?
Higher temperatures can produce more rapid growth, and in those conditions dangerous strains can grow without harm to anyone.
What are the advantages of vaccines?
- They had helped control diseases that were once common (e.g measles is controlled, smallpox no longer occurs)
- Epidemics can be prevented if a large percentage is vaccinated
What are the disadvantages of vaccines?
- Side effects e.g swelling/fever