infection and response

• How do bacteria spread

  Bacteria recproduce rapidly inside the body produce toxins that damage cells
• How do virus spread?

  Virus replicates themselves by using cell machinery causing the cell burst
• How can pathogens be spread

  By direct contact e.g touching contaminated surfaces/ skin By water e.g. drinking, bathing, cooking By air e.g. inhaling droplets of sneeze/coughs
• How can spread of disease be reduced?


  Vaccination - to provide immunity isolation - reduces contact with healthy people Hygeine - washing hands regularly, disinfecting surfaces Destroying vectors
• What is measles, symptoms, spread, reduced


  Viral disease measles: symptoms: Fever/ red skin rash How is it spread: inhalation of droplets of sneeze/ cough from infected person How can it be reduced/ prevented: isolation, most people vaccinated at a young age
• HIV


  Viral disease
• Progression of HIV


  1. Initially a flu like illness

  2. Then often no symptoms for years
• How HIV is spread

  • Sexual contact
  • Exchanging body fluids e.g. sharing needles
• How HIV is spread or prevented

  • Avoid sexual intercourse
  • Use a condom
  • Do not share needles
  • Antiretrovial drugs control HIV
• What is TMV

  Mosaic pattern of dicolouration of leaves resitricted growth due to lack of photosynthesis how is it spread: direct contact between healthy and diseased plant prevented/ reduced: remove infected plant/ wash tools in disinfectant
• salmonella: fever, cramps, vomitting, diareara due to toxins produced How is spread: food prepared in unhygenic conditions, prevention: vaccinate poultry wash hands before preparing food, disinfectant surfaces
• What is gonorrea


  bacterial disease

  thick/ yellow green discharge from vagina or penis pain when urinating spready by sexual contact prevent: use condoms antibotics
• Rose black spot


  A fungus
• Rose black spot

  • Caused by a fungus
  • Symptoms: purple/black spot on leaves, leaves turn yellow and drop early
  • Prevents growth as photosynthesis is reduced
  • Spreads in the environment by wind and water
• Preventing rose black spot

  1. Remove and destroy affected leaves

  2. Use fungicides to kill the bacteria
• Malaria


  caused by a protist symptoms: recurrent episodes of a fever and can be fatal prevent - prevent mosqitos from breeding, use mosqito nests - to avoid being bitten
• How the human body prevents the entry of pathogens


  1. Scabs form over cuts - acts as a barrier

  2. Antimicrobial secretions - kills bacteria

  3. Sebum oil / repels pathogens

  4. Nose: hair and mucus/ prevent pathogens that enter

  5. Trachea and bronchia: cilia wafts mucus up to the throat to be swallowed

  6. Stomach- contains HCL kills most pathogens in food/ swallowed mucus
• Phagocytosis


  WBC engulf/ digest and destroy pathogens
• WBC role


  1. Produce specific antibodies in response to an antigen on the surface of pathogen

  2. Antibodies bind to antigen on the surface making pathogen clump together so more can be engulfed

  3. Produce specific antitoxins in response to toxins

  4. Antitoxin counteract toxins
• Antibodies bind to antigen on the surface


  Pathogen clumps together so more can be engulfed
• Antitoxin produced by WBC

  Counteract toxins
• Antitoxin counteracting toxins


  So don't feel as ill
• Vaccination


  1. Small quantities of dead/inactive forms of pathogens are introduced in body

  2. Antigens on the surface of pathogens stimulate WBC to produce unique antibodies

  3. Memory cells remain in body

  4. If same pathogen re-enters body, memory cells respond quickly to produce correct antibodies in larger quantities

  5. Pathogens are killed before numbers are high enough to cause disease
• what are painkillers?

  painkillers and other medicines are used to treat symptoms of disease do not kill pathogens
• why is it difficult to develop drugs for viruses?

  virus reproduce inside cell diffucult to develop drugs that destroy viruses without also damaging cells/ tissues
• what are molochonial antibodies?

  antibodies produced from a single clone of cells specific to 1 biinding site on one protein antigen so can target a specific chemical or specific cell
• Producing monoclonal antibodies in the laboratory


  1. Inject mouse with specific antigen

  2. Mouse lymphocyte stimulate to make antibody specific to antigen

  3. Lymphocyte combine with tumour cell to make hybridoma cell

  4. Hybridoma cell divides rapidly like tumour cell and produces antibody

  5. Single hybridoma cell cloned to produce many identical cells producing same antibody

  6. Large amount of antibody collected and purified