health,disease and the development if medicines

• Health


  A state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity
• Being healthy is about more than just not being sick
• Even if someone is very physically fit, they still might be unhealthy if they have mental health issues or are socially isolated
• Disease


  A condition where part of an organism doesn't function properly
• Types of disease


  • Communicable
  • Non-communicable
• Communicable diseases


  • Can be spread between individuals
• Non-communicable diseases


  • Can't be transmitted between individuals
  • Include things like cancer and heart disease
• If you are affected by one disease

  It could make you more susceptible to others
• Pathogen


  Organisms such as viruses, bacteria, fungi and protists that cause communicable diseases
• Cholera


  • Caused by the bacterium Vibrio cholerae
  • Spreads via contaminated water sources
  • Prevented by ensuring access to clean water
• Tuberculosis


  • Caused by the bacterium Mycobacterium tuberculosis
  • Spreads through the air when infected individuals cough
  • Prevented by infected people avoiding crowded public spaces, practicing good hygiene and sleeping alone
• Malaria


  • Caused by a protist
  • Spreads via mosquitoes acting as animal vectors
  • Prevented by using mosquito nets and insect repellent
• Stomach ulcers


  • Caused by the bacterium Helicobacter pylori
  • Spreads via oral transmission, e.g. swallowing contaminated water or food
  • Prevented by having clean water supplies and hygienic living conditions
• Ebola


  • Caused by the Ebola virus
  • Spreads via bodily fluids
  • Prevented by isolating infected individuals and sterilising affected areas
• Chalara ash dieback


  • Caused by a fungus
  • Spreads through the air and by moving infected ash trees between areas
  • Prevented by removing young, infected ash trees and replanting with different species, and restricting the import or movement of ash trees
• Viruses


  Not cells, usually no more than a protein coat around a strand of genetic material
• Viruses


  • Have to infect living cells (called host cells) in order to reproduce
  • Specific types of viruses will only infect specific cells
• Life cycle of a virus


  1. Infect new host cell

  2. Reproduce by lytic pathway

  3. Can enter lysogenic pathway
• Lytic pathway


  • Virus attaches to host cell and injects genetic material
  • Virus uses host cell to replicate genetic material and produce new virus components
  • Viral components assemble
  • Host cell splits open, releasing new viruses
• Lysogenic pathway


  • Injected genetic material incorporated into host cell genome
  • Viral genetic material replicated with host DNA when host cell divides, but virus dormant
  • Eventually a trigger causes viral genetic material to leave genome and enter lytic pathway
• Chlamydia


  • A kind of bacterium that behaves like a virus as it can only reproduce inside host cells
  • Can result in infertility
  • Spread can be reduced by wearing condoms, screening and treatment, or avoiding sexual contact
• HIV is the Human Immunodeficiency Virus - it kills white blood cells, which are really important in the immune response
• AIDS (Acquired Immune Deficiency Syndrome)


  When HIV infection leads to the infected person's immune system deteriorating and eventually failing, making them vulnerable to opportunistic infections
• HIV


  • Spread via infected bodily fluids (e.g. blood, semen, vaginal fluids)
  • Can be prevented by using condoms, avoiding shared needles, and medication to reduce risk of transmission
• Plant leaves and stems


  • Have a waxy cuticle
  • Provides a barrier to stop pathogens entering or pests from damaging them
  • May stop water collecting on the leaf, reducing risk of infection by pathogens transferred in water
• Plant cells


  • Surrounded by cell walls made from cellulose
  • Form a physical barrier against pathogens that make it past the waxy cuticle
• Plants


  • Produce chemicals that help prevent damage to the plant
  • Produce antiseptics that kill bacterial and fungal pathogens
  • Produce chemicals to deter pests (e.g. insects) from feeding on their leaves
• Chemicals produced by plants


  • Quinine from the bark of the cinchona tree (used to treat malaria)
  • Aspirin from the bark and leaves of willow trees (used to relieve pain and fever)
• Detecting plant diseases


  1. Observations to recognise symptoms

  2. Analysing distribution of diseased plants to identify pathogen

  3. Laboratory-based diagnostic testing (detecting antigens, detecting DNA)
• Antigens


  Unique molecules on the surface of pathogens
• Pathogen DNA


  Present in infected plant tissues, can be detected to identify the pathogen
• Human skin


  • Acts as a barrier to pathogens
  • Blood clots quickly to seal cuts and keep microorganisms out
• Nose and airways


  • Hairs and mucus trap particles that could contain pathogens
  • Cells produce mucus that traps pathogens, cilia waft mucus up to be swallowed
• Stomach


  • Produces hydrochloric acid that kills most swallowed pathogens
• Eyes


  • Produce lysozyme (in tears) which kills bacteria on the eye surface
• Immune system


  • White blood cells patrol for pathogens
  • B-lymphocytes produce antibodies specific to pathogens' antigens
  • Memory lymphocytes 'remember' specific antigens
• 1st exposure to antigen


  Slow immune response, symptoms of disease
• 2nd exposure to same antigen

  Faster, stronger immune response, often clears pathogen before symptoms
• Immunisation


  Injecting dead or inactive pathogens to trigger antibody production and memory lymphocytes
• Immunisation makes it less likely you'll get ill from the disease