pathogens and disease

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  • Pathogens and Disease
    • What is a disease?
      • A disease is a physical or mental disorder that has set symptoms
    • Pathogens
      • Include bacteria, fungi, and viruses
      • Pathogens can cause disease in numerous ways...
        • Production of toxins
        • Rupturing a cell by releasing nutrients such as proteins inside the cell
        • staving the host cell by breaking down the nutrients within them
        • replication within a host cell can cause it to burst
      • The ability for a pathogen to cause disease depends on these things..
        • Location - what tissue is colonised
        • Infectivity - how easily a bacterium can enter the host cell
        • Invasiveness - how easily a bacterium or its toxin spreads within the body
        • Pathogenicity - how a bacterium causes disease
    • Lifestyle choices
      • Poor lifestyle choices can lead to a person being more at risk to certain diseases...
        • Cancer
          • Smoking
          • Exposure to sunlight
          • Alcohol
        • Coronary Heart Disease
          • Poor diet
            • High in saturated fat or salt
          • Smoking
          • Lack of exercise
          • alcohol
      • Changing a lifestyle for the better wont get rid of the chance of getting a disease, but it will reduce the likely hood of the disease develpoing
    • The Immune System
      • Phagocytes engulf pathogens...
        • a phagocyte recognizes that a pathogens antibodies are foreign
          • The Cytoplasm moves around the pathogen and contains it in the phagocytic vacuole
            • Lysosomes then break down the pathogen
              • The phagocyte places antigens on its surface to activate T-Cells
                • T-Cells are a type of white blood cell. They either activate B-Cells or kill pathogens
                  • B-Cells are white blood cells that are covered in antibodies
                    • The antibodies of the B-Cell binds with the pathogen to form a antigen-antibody complex
                      • B-Cells divide into Plasma Cells. These have many functions...
                        • They coat the pathogen to make it easier for the phagocyte to engulf it
                        • They coat the pathogen to prevent it from entering host cells
                        • They bind with the pathogen to neutralise toxins it produces
      • Primary Responce
        • The Immune System is alerted for the first time
          • The production of B-Cells is slow, eventually the person will have enough of the correct antibodies but this takes a long time
      • Secondary Responce
        • If the same pathogen re-enters the body the Immune system already has the memory B-Cells which divide into Plasma cells and memory T-Cells that create the correct T-Cells and kill the pathogen
          • Pathogens in the secondary responce are usually killed before the host shows symptoms
      • Vaccines
        • vaccines contain antigens which cause the body o produce memory cells against a pathogen
          • Herd Immunity- when people who haven't been vaccinated are less likely to get a disease because it is less common
          • The antigens of a vaccine may be free or attached to a weakened pathogen
          • Taking vaccines orally may cause the antibodies to be digested in the stomach or they may be too big to be diffused into the bood, so many vaccines are injected
      • Antigenic Variation
        • pathogens may alter the antigens on its surface to re-start primary responce
    • monoclonal antibodies
      • drugs are attached to B-Cells which are injected into the infected person
        • the B-Cell binds with the specific cells and destroys them, reducing the number of side effects


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