* Health, Disease & the Development of Medicines

• The World Health Organisation (The WHO) defines health as ''a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity''.
• Communicable diseases are diseases that can be spread between individuals.
• Non-communicable diseases can't be transmitted between individuals. They include things like cancer and heart disease.
• Pathogens are organisms such as viruses, bacteria, fungi, and protists that cause communicable diseases.
• What is the pathogen that causes Cholera ?

  a bacterium called Vibrio cholerae
• What are the symptoms/effects of Cholera ?

  diarrhoea
• How does Cholera spread ?

  by contaminated water sources
• How can we reduce/prevent the transmission of Cholera ?

  making sure that people have access to clean water supplies
• What pathogen causes Tuberculosis ?

  a bacterium called Mycobacterium tuberculosis
• What are the symptoms/effects of Tuberculosis ?

  coughing and lung damage
• How does Tuberculosis spread ?

  through the air when infected individuals cough
• How can we reduce/prevent the transmission of Tuberculosis ?

  infected people should avoid crowded public spaces, practise good hygiene and sleep alone, their homes should also be well-ventilated
• What is the pathogen that causes Malaria ?

  a protist
• What are the symptoms/effects of Malaria ?

  damage to red blood cells and in severe cases, to the liver
• How does Malaria spread ?

  mosquitos act as animal vectors (carriers) - they pass on the protists to humans but don't get the disease themselves
• How can we reduce/prevent the transmission of Malaria ?

  use mosquito nets and insect repellent to prevent mosquitos carrying the pathogen from biting people
• What is the pathogen that causes Stomach Ulcers ?

  a bacterium called Helicobacter pylori
• What are the symptoms/effects of Stomach Ulcers ?

  stomach pain, nausea and vomiting
• How do Stomach Ulcers spread ?

  oral transmission
• How can we reduce/prevent the transmission of Stomach Ulcers ?

  having clean water supplies and hygienic living conditions
• What is the pathogen that causes Ebola ?

  ebola virus
• What are the symptoms/effects of Ebola ?

  via bodily fluids
• How can we reduce/prevent the transmission of Ebola ?

  by isolating infected individuals and sterilising any areas where the virus may be present
• What pathogen causes Chalara ash dieback ?

  a fungus that infects ash trees
• What are the symptoms/effects of Chalara ash dieback ?

  leaf loss and bark lesions
• How does Chalara ash dieback spread ?

  carried through the air by the wind
• How can we reduce/prevent the transmission of Chalara ash dieback ?

  removing young, infected ash trees and replanting with different species
• Viruses aren't cells. They're usually no more than a protein coat around a strand of genetic material. They have to infect living cells in order to reproduce. Specific types of viruses will only infect specific cells.
• The Lytic Pathway:

  • the virus attaches itself to a specific host cell and injects its genetic material into the cell
  • the virus uses proteins and enzymes in the host cell to replicate its genetic material and produce the components of new viruses
  • the viral components assemble
  • the host cell splits open, releasing the new viruses, which infect more cells
• The Lysogenic Pathway:

  • the injected material is incorporated into the genome (DNA) of the host cell
  • the viral genetic material gets replicated along with the host DNA every time the host cell divides - but the virus is dominant and no new viruses are made
  • eventually a trigger causes the viral genetic material to leave the genome and enter the lytic pathway
• HIV is the Human Immunodeficiency Virus - it kills white blood cells, which are really important in the immune response.

  HIV infection eventually leads to AIDS.
• Most plant leaves and stems have a waxy cuticle, which provides a barrier to stop pathogens entering them or pests from damaging them.

  Plant cells themselves are surrounded by cell walls made from cellulose. These form a physical barrier against pathogens that make it past the waxy cuticle.
• Quinine comes from the bark of the cinchona tree. For years it was the main treatment for Malaria.
• Aspirin is used to relieve pain and fever. It was developed from a chemical found in the bark and leaves of willow trees.
• Detecting Antigens:

  • pathogens have unique molecules on their surface called antigens
  • antigens from a particular pathogen will be present in a plant infected with that pathogen and can be detected in a sample of plant tissue
  • the detection of an antigen unique to a particular pathogen allows that pathogen to be identified and the disease diagnosed
• Detecting DNA:

  • if a plant is infected with a pathogen, the pathogen's DNA will be present in the plant's tissues
  • scientists have techniques that allow them to detect even small amounts of pathogen DNA in a sample of plant tissue, allowing them to identify the particular pathogen that is present
• Physical Barriers:

  • the skin acts as a barrier to pathogens and if it gets damaged, blood clots quickly seal cuts and keep microorganisms out
  • hairs and mucus in your nose trap particles that could contain pathogens
  • cells in your trachea and bronchi also produce mucus, which traps pathogens - they are hair-like structures which waft the mucus up the back of the throat where it can be swallowed
• Chemical Barriers:

  • the stomach produces hydrochloric acid, this kills most pathogens that are swallowed
  • the eyes produce a chemical called lysozyme which kills bacteria on the surface of the eye
• B-lymphocytes are a type of white blood cell that are involved in the specific immune response - this is the immune response to a specific pathogen.
• Memory lymphocytes are produced in response to a foreign antigen. They stay in the body for a long time and remember a specific antigen.