Infection and response

• Pathogens


  Microorganisms that cause infectious disease

  -cause communicable diseases
• Pathogens can be...


  -viruses

  -bacteria

  -protisits

  -fungi
• Pathogens are spread by

  air, direct contact, water
• Bacteria and viruses reproduce...

  Rapidly inside the body
• Bacteria may produce ...

  Toxins that damage tissues and make us feel ill
• Viruses


  Live and reproduce inside cells

  -causing cell damage
• Protisits


  single celled eukaryote

  -some are parasites

  -often transferred by vector
• fungi


  Single-called

  -hyphae grows and penetrates skin and surfaces causing diseases
• Measles


  viral disease

  symptoms: fever, red skin rash

  -serious illness can be fatal if complications arise

  -spread by inhalation of droplets from sneezes and coughs
• HIV


  Viral disease

  Symptoms: flu-like

  -unless successfully controlled with antiretroviral drugs the virus attack the body's immune cells

  -late HIV -> AIDS (when body immune system is so damaged it can no longer deal with other infections/cancers)

  -spread 0by sexual contact or exchange in body fluids (needles
• Tobacco Mosaic Virus (TMV)


  Viral disease

  Symptoms: mosaic pater of discolouration on the leaves which affects the growth of the plant due to lack of photosynthesis
• Salmonella


  Bacterial disease

  Symptoms: fever, abdominal cramps, vomiting and diarrhoea

  -spread by bacteria ingested in food or food prepared in unhygienic a conditions

  -poultry are vaccinated against salmonella to control the spread
• Gonorrhoea


  Bacterial disease

  Symptoms: thick yellow/green discharge from the vagina or penis and pain while urinating

  -spread by sexual contacts STD

  -was treated with antibiotic penicillin until many resistant strains appeared

  -spread can be controlled by treatment of antibiotics and the use of a barrier method of contraception such as a condom
• Rose black spot


  Fungal disease

  Symptoms: purple/black spots which often turn yellow and drop early

  -affects the growth of plant as photosynthesis produced

  -spread in the environment by water/wind

  -treated with fungicides and removing/destroying affected leaves
• Malaria


  Protist disease

  Symptoms: recurrent episodes of fever and can be fatal

  -spread by vectors

  -reduce spread by preventing mosquitos breeding and using mosquito nets to avoid being bitten
• Human defence systems


  Skin, nose, trachea and bronchi, stomach
• Skin


  -acts as a barrier

  -oil (sebum) on the surface that repels pathogens

  -scabs form over cuts- from a barrier (platelets)
• Eyes


  -produce tears

  -tears are antiseptic

  -contain enzyme to kill bacteria
• Trachea and bronchi and nose

  -contain mucus

  -which is sticky and traps bacteria

  -mucus is carried away by cilia
• White blood cells defend against pathogens by:

  Phagocytosis, antibody production, antitoxin production
• Antitoxins


  Counteract toxins produced by invading bacteria

  (Neutralise them)
• Antibody


  -bind pathogens ready for phagocytosis

  -this destroys them

  -triggers a memory cell to produce a rapid response if pathogen renters
• vaccination


  -introduce small quantities of dead or inactive pathogens to stimulate WBC to produce antibodies

  -so if same pathogen re-enters the body the WBC respond quickly to produce correct antibodies preventing infection
• Spread of disease reduced by

  -being hygienic

  -destroying vectors

  -isolating effected individuals

  -vaccination
• Medicine that help to cure bacterial disease by killing infective bacteria

  Antibiotics

  -penicillin
• Antibiotics cannot kill


  Viral pathogens
• Painkillers


  Used to treat the symptoms of disease but do not kill pathogens.
• Where does the heart drug digitalis originate from?

  Foxgloves
• The painkiller aspirin originates from


  willow
• penicillin originates from


  Penicillium mould
• Drugs are tested on

  Toxicity , efficacy and dose
• Preclincal Testing


  Done in a laboratory using cells, tissues and live animals
• Clinical trials


  -use healthy volunteers

  -very low does given at start of trials

  -if drug found to be safe, further comical trials are carried out to find optimum dose for drug
• Double blind trials


  experiments in which neither the subjects nor the examiners know whether the treatment is the active treatment, or a placebo
• monoclonal antibodies


  -produced from a single clone of cells

  -the antibodies are specific to one binding site on one protein antigen so are able to target a specific chemical cells in the body
• Production of monoclonal antibodies

  -stimulating mouse lymphocytes to make a particular antibody

  -lymphocytes are combined with a particular kind of Tumor cells to make a cell called a hybridoma cell

  -hybridoma cell can both divide and make the antibodies

  -single hybridoma cells are cloned to produce many identical cells that all produce the same antibody

  -large amount of the antibody cab be collected and purifies
• monoclonal antibodies in pregnancy tests


  -when urine is applied to the application area (which contains complementary antibodies to hCG protein, bound to blue beads) any hCG (hormone found in urine of pregnant women) will bind to the antibody on the beads

  -the urine moves up the stick, carrying the beads with it

  -the urine moves to the test strip (containing immobilised antibodies complementary to hCG)

  -if hCG is present, immobilised antibodies stick to the hCG with blue beads attached so the strip turns blue

  -if no hCG is present, the beads pass the strip without binding so no colour change
• Plant diseases can be detected by

  • stunted growth

  • spots on leaves

  • areas of decay (rot)

  • growths

  • malformed stems or leaves

  • discolouration

  • the presence of pests.
• identification can be made by:

  - reference to a gardening manual or website

  - taking infected plants to a laboratory to identify the pathogen

  - using testing kits that contain monoclonal antibodies.
• Stunted growth caused by

  Nitrate deficiency

  -needed for protein synthesis