Infection and response

• pathogens are microorganisms that enter through the body and cause disease
• bacteria are very small cells that make you feel ill by producing toxins that damage your cells and tissues
• viruses are tiny and live inside your cells and replicate themselves using cells machiery to produce many copies of themselves which causes the cells to burst, the cell damage is what makes you feel ill
• protists are eukaryotes and some are parasites living in or on other organisms and cause them damage
• some fungi have body of hyphae that can grow and penetrate human skin and the surface of plants, causing disease, they can also produce spores which can spreads to other plants and animals
• pathogens can spread by:

  water - drinking or bathing in dirty water

  air - breathed in pathogens

  direct contact - touching contaminated surfaces
• measles is a viral disease:

  develop red skin rash and signs of fever

  most people are vaccinated
• HIV is a viral disease:

  flu like symptoms

  attacks immune cells
• Tobacco mosaic virus is a viral disease:

  affects many species of plants

  this causes discolouration

  the discolouration means the plant cant carry out photosynthesis well
• rose black spot is a fungal disease:

  causes purple or black spots to develop on leaves of rose plants

  means less photosynthesis can happen

  gardeners treat by using fungicides and stripping plant of affected leaves
• Malaria is caused by a protist:

  mosquitoes are vectors and every time they feed it infects the animal by inserting the protist into the animals blood vessels

  causes repeated episodes of fever
• salmonella is a bcaterial disease:

  causes fever, stomach cramps, vomiting and diarrhoea

  symptoms caused by the toxins the bacteria produce

  get salmonella by eating contaminated food

  most poultry in the UK are given a vaccination against it
• gonorrhoea is a bacterial disease:

  transfered by sexual contact

  causes pain when urinating and yellow or green discharge

  antibiotics help stop the spread
• Gonorrhoea

  A bacterial disease that is transfered through sexual contact and causes pain when urinating and yellow or green discharge. Antibiotics can help stop the spread of the infection.
• the skin acts like a barrier to pathogens
• hairs and mucus in your nose trap particles that could contain pathogens
• the trachea and brochi screte mucus to trap pathogens
• the stomach produces hydrochloric acid that kills pathogens that make it far from the mouth
• white blood cells engulf foreign cells and digest them, this is called phagocytosis
• some white blood cells will produce proteins and antibodies to lock onto invading cells so that they can be found and destroyed by other white blood cells
• white blood cells produce antitoxins counteracting toxins produced by invading bacteria
• vaccinations involve:

  injecting small amounts of dead or inactive pathogens

  these carry antigens

  body produces antibodies to attack them
• pros of vaccination:

  control communicable diseases

  prevent epidemics
• cons of vaccination:

  don't always work

  can cause a bad reaction
• antibiotics kill bacteria causing the problem without killing your own body cells
• antibiotics don't destroy viruses
• aspirin is used as a painkiller and developed from a chemical in willow trees
• digitalis is used to treat heart conditions and is developed from a chemical found in foxgloves
• in preclinical testing the drugs are tested on human cells and tissues

  the next step is testing the drug on live animals to test efficacy and dosage
• in clinical trials the drug is tested on healthy volunteers to make sure the test doesn't have side effects at low dosages

  it is then tested on patients to find the optimum dose
• to test how well a drug works patients are put randomly in two groups with one having the drug and the other the placebo, neither the patient or the doctor knows what group has the placebo so its a double-blind test, the results are put through peer review
• antibodies are produced by lymphocytes
• in monoclonal antibodies a tumour cell and lymphocyte cells are fused to create a cell called a hybridoma
• to make monoclonal antibodies a mouse is injected with the chosen antigen

  the lymphocytes are taken from the mouse and fused with a tumour cell making a hybridoma cell

  it divides quickly to produce lots of clones that produce the monoclonal antibodies
• cancer cells have antigens on their cell membranes called tumour markers

  in the lab you can make monoclonal antibodies that will bind to these tumour markers

  an anti-cancer drug can be attached to these monoclonal antibodies

  the drug kills the cancer cells but doesn't kill any normal body cells near the tumour
• monoclonal antibodies advantages:

  cancer treatment

  pregnancy tests

  disadvantages:

  cause side effects
• Nitrates are needed to make proteins and therefore growth. lack of nitrates causes stunted growth
• magnesium ions are needed for making chlorophyll, which is needed for photosynthesis. plants without magnesium suffer from chlorosis and have yellow leaves
• if plants have disease they will:

  have stunted growth

  abnormal growths

  spots on leaves

  malformed stems or leaves

  patches of decay

  discolouration
• to identify plant disease:

  looking in gardening manuals or gardening websites

  take infected plant to a laboratory

  using testing kits with monoclonal antibodies