Topic 10: Diseases and Immunity

• Viruses are known as the smallest organisms and consists a fragment of genetic material inside a protective protein coat.
• Viruses can reproduce inside host cells and damage the cells, It can get into the host cells and once it produces copies, it'll fill the whole host cell and burst it open.
• Viruses will then be passed out in the bloodstream, airways or other routes.
• Antibiotics are substances that damage the cell wall of a bacteria, since bacteria has a cell well therefore able to destruct the cell wall and stop enzymes for growth.
• Antibiotics don't work on viruses because they don't have a cell wall and attacks inside the body so it's difficult to kill without damaging body growth.
• Bacteria and viruses don't contain nucleus, viruses don't have cytoplasm.
• Virus Structure

  • Capsid: contains genetic material (DNA or RNA)
• If pathogen enters the body, it is likely to meet a large number of lymphocytes, it will then recognise the pathogen as being something that its antibody can destroy. Lymphocyte will start to divide rapidly by mitosis cell division making clones of lymphocytes and then secrete their antibody destroying the pathogen.
• Immunity

  Active: Long term

  • protection/defence against pathogen
  • produce own antibiotics
  • keep memory cells for quicker antibody production in future infections by the same pathogen/antigen
• Body Defenses:

  Mechanical Barriers: limited to skin and hairs in the nose.
• Antibodies

  • produced by lymphocytes
  • lymphocytes will be stimulated to produce antibodies when it contacts with pathogen/antigen
  • able to recognise pathogen and bind to the antigen which is found on the surface and help to destroy the pathogen.
  • always in Y shape and made up of proteins
  • antibodies lock onto antigens leading to direct destruction of pathogens or marking of pathogens for destruction by phagocytes.
• Antigen

  • a protein or carbohydrates on the surface of pathogens.
  • able to provoke a immune system of the host.
  • has specific shape so can fit the specific shapes of the antigen binding site on the antibodies
  • present on the surface of pathogens and can be found on the surface of donor's organ.
• Process of Vaccination

  : control the spread of diseases

  • antibodies produced by the body to combat invasion by pathogen can enhanced by vaccines.
• Where will the viruses be passed down?

  bloodstream, airways or other routes
• Why antibiotics don't work on viruses?

  It is because viruses don't contain a cell wall and attacks inside the body.
• What is the viral envelope?

  Made from fatty lipid molecules in host cells in the host organism
• Vaccines: dead or weakened pathogen injected into the body to provoke the body's immune system to make appropriate antibodies.

  • this is to produce memory cells giving long-term immunity and for faster antibody production in future infections by the same pathogen/antigen.
• Immunity

  Passive: Short term

  • protective against pathogen
  • take other individual antibodies
  • do not keep memory cells
• Body defenses:

  Chemical Barriers: limited to mucus, tears and stomach acidCells, limited phagocytes and lymphocytes (phagocytosis and antibody production by white blood cell) can be enhanced by vaccination.
• Virus Structure:

  • Viral envelope: is made from fatty lipid molecules taken from cells in the host.
• Virus Structure:

  • virus genetic material: contains genetic material which contains instructions for making new copies of the virus.
• Virus Structure:

  • Surface proteins: help the virus recognise and bind to cells in the host organism.