health, disease & the development of medicines

• Malnutrition


  Malnutrition caused by a diet high in sugars and fats can lead to obesity, where large amounts of fats are formed under the skin and around organs, like the heart or kidneys.

  We need some fats to cushion organs when we move , to store some vitamins, and to provide a store of energy. Too much fat can increase the risk of many diseases.
• Heart diseases


  Tobacco smoke contains many harmful substances that can damage the lungs. These can damage blood vessels, increase blood pressure, make blood vessels narrower and increase the chance of blood clots forming. A narrowed blood vessel can be widened by inserting a small mesh tube (stent) at the narrowest part to hold it open.

  Blocked arteries in the heart can be bypassed by inserting other blood vessels so that the heart tissue is supplied with oxygen and nutrients again. Patients that have to take medicines for the rest of their life to help prevent a heart attack or stroke.
• Plant diseases (visible symptoms)


  The first signs of plant diseases are generally visible symptoms and will be the first step in identifying the disease.

  Identifying them:

  • change in normal appearance of plant, eg. change in colour of leaves
  • overgrowth of part of plant, eg swelling (gals) on roots
  • death of parts of the plant, eg dead leaves
  • under-development of part of plant, eg smaller leaves than usual
• Plant diseases (distribution analysis)

  some questions you may ask:

  • how many plants are affected? If they are all affected it is probably an environmental factor, eg soil pH
  • Where are disease plants found? All over, or just in one place, eg next to a road which might indicate pollution?
  • is it just one species of plant affected or several? This might tell you whether it is a species-specific pathogen
  • Do the symptoms of the plant change over time. This might help you to distinguish one disease from another
• Antibiotics 


  Antibiotics are substances that either kill bacteria or inhibit their cell processes, which stops them growing or reproducing. Antibiotics do not have this effect on human cells. This makes them useful for attacking bacterial infections that the immune system cannot control. Antibiotics are substances that either kill bacteria or inhibit their cell processes, which stops them growing or reproducing. Antibiotics do not have this effect on human cells. This makes them useful for attacking bacterial infections that the immune system cannot control.
• Human defences (chemical)


  Defences:

  • lysozyme enzyme in tears kills bacteria by digesting their cell walls
  • lysozyme enzyme is also present in saliva and mucus and also does this
  • hydrochloric acid in stomach acid kills pathogens in food and drink
• Human defences (physical)


  Defences:

  • unbroken skin forms a protective barrier because it is too thick for most pathogens to get through
  • sticky mucus in the breathing passages and lungs trap pathogens. Cilia on the cells lining the lungs move in a wave-like motion, moving ,mucus and trapped pathogens out of the lungs towards the back of the throat where it is swallowed.
• Plant defences (chemical)


  Plants protect themselves from attack by producing chemicals. They make:

  • poisons in their cells to deter pests that try to eat them
  • chemicals that kill pathogens (such as bacteria and fungi), which infect them and cause disease.
• Plant defences (physical)


  Many plants have bark and a thick waxy cuticles (outer covering of a leaf) that are difficult for a pest to get through.

  Some have adaptions such as spikes and thorns to stop pests from eating them.

  Cellulose cell walls are difficult for pathogens to break down unless they produce a suitable enzyme.
• Pathogens


  Pathogens include bacteria and viruses, fungi and protists. When a few pathogens infect you they can reproduce very rapidly. Large numbers of pathogens will make you ill.
• Types of diseases (communicable)


  Communicable diseases are diseases that can be spread.

  Characteristics:

  • rapid variation in number of cases over time
  • cases often localised
  • examples are malaria, typhoid and cholera
• Types of diseases (non-communicable)


  Non-communicable diseases are diseases that cannot be spread.

  Characteristics:

  • gradual change in number of cases over time
  • cases widely spread
  • examples are cancer, diabetes and heart disease
• Vaccines


  1. A vaccine contain antigens from the pathogen, often in the form of dead or weakened pathogens.
  2. The person's lymphocytes produce antibodies against the pathogen and also memory lymphocytes.
  3. If the person becomes infected with the real pathogen, the memory lymphocytes will give a very rapid secondary response to the pathogen. This means the person is unlikely to become ill.
• Immunisation


  Advantages:

  • immunity is produced without being ill
  • immunity lasts a long time, often for life
  • if most people are immune, than the few people who are unvaccinated are also less likely to catch the disease. This is called herd immunity.

  Disadvantages:

  • some people get a mild reaction of swelling or soreness, or get a mild form of the disease
  • very rarely a person has a major, harmful reaction
• Spreading pathogens


  Airborne spread - coughs/sneezes send tiny water droplets into the air. Fungi produce tiny spores that can be spread through the air.

  Water spread - pathogens in drinking/washing water, more often where there are poor standards of hygiene as stopped by water treatment.

  Oral route - spread by food/drinks/contact entering the mouth. People/ flies spread pathogens by touching food then touching their mouths.

  Vector spread - malaria is caused by a protist that is carried in blood that mosquitoes have fed off.
• Monoclonal antibodies


  B lymphocyte from mouse

  • advantage - makes particular antibodies
  • disadvantage - B lymphocyte doesn't divide

  Cancer cell

  • advantage - divides continuously
  • disadvantage - doesn't make antibodies

  Forms:

  • hybridoma cell formed by fusing a B lymphocyte and a cancer cell
  • the hybridoma cell divides and produces antibodies that are all the same
• Lytic cycle


  1. Virus attaches to the host cell.
  2. Virus enters cell and injects its DNA or RNA into the cell.
  3. Virus RNA or DNA copies itself and causes new virus proteins to be made, using the organelles in the host cell.
  4. The DNA or RNA and virus proteins are packed together to make new viruses. These are released from the cell, which usually destroys the host cell.
• Lysogenic cycle


  In the lysogenic cycle, the virus inserts its DNA into the chromosomes of the host cell. It is called a provirus. The provirus replicates with the rest of the host DNA every time the host cell divides. The provirus can stay dormant for a long time like this. At some stage, the provirus can become active and make new viruses in the lytic cycle.
• The immune system


  1. Each pathogen has unique antigens on its surface.
  2. A lymphocyte with an antibody that fits the antigen is activated.
  3. The lymphocyte divides many times to produce clones of identical lymphocytes.
  4. Some of the lymphocytes produce lots of antibodies which stick to the pathogen and destroy it. Other lymphocytes stay in the blood as memory lymphocytes ready to respond immediately if the same antigen returns.
• Antibiotics (core practical) Pt.1

  Method:

  1. Turn the bacterial plate upside down and mark the base into sections - 1 per test disc. Label each section with the substance or concentration.
  2. Turn the plate the right way up. Lift the lid of the dish just enough to be able to place a disc on the lawn.
  3. Use the sterile forceps to place a paper disc on the bacterial lawn. Then briefly flame the forceps in a blue Bunsen burner flame to sterilise them.
  4. Repeat step 3 for each disc.
  5. Tape the lid tot he base of the dish without completely sealing it.
  6. Incubate it at $25^{\circ}C$ for a few days.
• Antibiotics (core practical) Pt.2

  Apparatus - bacterial lawn plate, paper discs soaked in test substances,  sterile forceps, sticky tape, marker pens, Bunsen burner and heat proof mat

  Conclusion - the bigger the diameter around the disc, the better the substance is at killing bacteria