B1: Preventing Disease

What is a pathogen?
1. A pathogen is a bacterium, virus or other microorganism that can cause disease.
2. A pathogen can consist of:
  1. Bacteria
    1. How do bacteria cause harm?
      1. Bacteria can cause certain diseases such as:
        Food poisoning.
        Cholera.
        Typhoid.
        Whooping cough.
        Gonorrhoea.
      2. Bacteria release toxins and poisons, making us feel ill.
    2. Bacteria are living microorganisms that are microscopic. They multiply rapidly in favourable conditions and release poisons or toxins that make us feel ill.
      1. Bacteria reproduce quickly asexually.
      2. Bacteria can mutate to gain antibiotic resistance, to a certain antibiotic. Once a bacterium mutates for antibiotic resistance, they survive because of natural selection and over time all of the organisms in the species will have the resistance. When a bacterium mutates, it usually dies, but sometimes, it can be beneficial.
        What is a mutation?
        A mutation is random altering of genetic information of an organism. Usually mutating organisms die but sometimes it can give positive characteristics to an organism.
        How can mutations be prevented?
        By taking all the antibiotics in a prescribed course, making sure all bacteria are killed and cannot reproduce / mutate.
        And by not overprescribing drugs, so that there is less of a chance of bacteria mutating to survive.
        By improving cleanliness, washing hands, etc. means that you will kill bacteria on surfaces and there will be a lesser chance of someone catching the bacteria. This will mean the spread of the pathogen will decrease.
    3. A bacterium that is resistant to lots of antibiotics is called a 'superbug'.
  2. Viruses
    1. Viruses are many times smaller than bacteria and carry a fragment of genetic material inside a protective protein coat. They reproduce inside host cells and damage the body doing so, they reproduce making thousands of copies of themselves, and then burst the cell open and pass on to other places in the body.
    2. How do viruses cause harm?
      1. They have to use a host to duplicate. They will enter a cell and use its machinery to reproduce. Viruses will fill the cell and then the cell membrane will burst open, releasing the viruses into other parts of the body. Viruses carry harmful genetic information and can cause disease.
  3. Fungi
  4. Protozoa (single-celled organisms)
The immune system
1. White blood cells
  1. White blood cells defend the body in 3 ways - 1. ingesting the pathogen, 2. Producing antibodies to destroy the pathogen, 3. Producing antitoxins to break down the toxins made by bacteria.
    1. Things to remember:
      1. Antibodies and antitoxins are non-Latin. They are just specialised proteins.
      2. Pathogens are not the disease. Pathogen cause the disease.
      3. White blood cells don't 'eat' the pathogen, they 'ingest' it.
  2. Phagocytes can easily pass through blood vessel walls and into the surrounding tissue to move towards pathogens or toxins. They can ingest the pathogens or toxins, or release enzymes to destroy them.
  3. Pathogens contain certain chemicals that are foreign to the body that are called antigens. Each lymphocyte carries a specific antibody which attacks antigens that pathogens release. They can bind to pathogens and destroy them, and clump them together so that phagocytes can ingest them.
Vaccines
1. What is an immunisation?
  1. A way of inserting a vaccine into the body (such as injection).
2. What is a vaccine?
  1. A collection of dead or inactive pathogens, meant to trick the body into fighting it off for future protection.
3. Vaccines protect you like so: The vaccine is inserted into you containing inactive forms of a pathogen through an immunisation. This triggers your immune system to produce white blood cells to attack the pathogen. The white blood cells will neutralise the pathogen without you feeling ill, your immune system remembers the certain pathogen and the antigens it produced for if it returns to the body again and it is detected, the immune system will produce white blood cells at a heightened rate to destroy the pathogen. This means you are 'immune' to the disease.
Antibiotics
1. What are antibiotics?
  1. Antibiotics are chemicals that destroy certain bacteria and do not affect the body's cells. Antibiotics can only target bacteria.
2. Antibiotics can only target bacteria, they cannot target viruses because they don't work within cells. Antibiotics sometimes harm healthy bacteria though. Antibiotics usually works by destroying the cell wall of the bacteria.
3. The first antibiotic was founded by Alexander Fleming, in 1928. He left his petri dishes open and found that a mould, was growing in it. He found that were the mould was, bacteria was killed. This was the first antibiotic and it was called penicillin, it was used to prevent bacterial diseases such as Scarlet Fever.

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	Criado por Nikita Sitinikovs quase 8 anos atrás