B3-infection and response

• Pathogens


  Microorganisms that cause diseases which spread between organisms
• Diseases


  • Purple/black fungus (Rose black spot)
  • Malaria (Protist)
  • Salmonella (Bacterium)
  • Gonorrhoea (Bacterium)
  • Measles (Virus)
  • HIV (Virus)
  • Tobacco mosaic virus (TMV) (Virus)
• Rose black spot


  • Water spots on leaves, can fur yellow and drop off, Reduced growth
• Malaria


  • Fever, Can be fatal
• Salmonella


  • Stomach cramps, Vomiting, Diarrhoea
• Gonorrhoea


  • Pain when urinating, Yellow/green discharge from vagina or penis, Fever
• Measles


  • Red skin rash
• HIV


  • Flu-like (initially), A damaged immune system (late stage Infection/AIDS)
• Tobacco mosaic virus (TMV)


  • Mosaic pattern on leaves, which reduces photosynthesis and growth
• How diseases are spread

  1. Fungus (Rose black spot): Water

  2. Malaria (Protist): Mosquito vectors

  3. Salmonella (Bacterium): Eating contaminated food

  4. Gonorrhoea (Bacterium): Sexual contact

  5. Measles (Virus): Airborne droplets (coughs and sneezes)

  6. HIV (Virus): Sexual contact, Exchanging bodily fluids (e.g. blood)

  7. Tobacco mosaic virus (TMV): Direct contact between plants
• Prevention and treatment


  • Removing and destroying infected leaves, Fungicides
  • Mosquito nets, Stop mosquitoes from breeding
  • Vaccination of poultry, Hygienic food preparation
  • Condoms, Antibiotics
  • Vaccination of children
  • Condoms, Antiretrovirals, Avoid sharing needles
  • You don't need to know how TMV is prevented
• Four Non-Specific Defence Systems Against Pathogens

  • Skin - acts as a barrier and secretes antimicrobial substances to kill pathogens
  • Trachea and bronchi - mucus traps pathogens, and cilia waft mucus up to the throat so that it can be swallowed
  • Nose hairs and mucus - trap particles containing pathogens
  • Stomach - hydrochloric acid kills pathogens
• Three Ways White Blood Cells Attack Pathogens

  • Phagocytosis - white blood cells engulf and digest pathogens
  • Producing antibodies - white blood cells produce antibodies specific to pathogens
  • Producing antitoxins - these counteract toxins produced by invading bacteria
• Types of Drugs


  • Antibiotics - kill pathogens
  • Specific antibiotics - target specific types of pathogens
  • Painkillers - relieve symptoms but don't target the pathogen
  • Vaccination - uses dead or inactive pathogens to stimulate antibody production
• Use of antibiotics can lead to antibiotic resistance, making it hard to treat infections
• Vaccinating a large proportion of the population greatly reduces the spread of pathogens, so that even people who aren't vaccinated are unlikely to catch the disease
• If live pathogens of the same kind try to attack, they are quickly recognised and attacked by antibodies produced from previous vaccination
• New drugs must go through extensive testing before being approved for use
• Types of Drugs


  • Antibiotics
  • Digitalis
  • Aspirin
  • Painkillers
  • Penicillin
• Antibiotics


  Kill bacteria
• Specific antibiotics


  • Kill specific types of bacteria
• Digitalis


  Heart drug
• Painkillers


  Treat the symptoms of disease but don't kill pathogens
• Penicillin source


  Penicillium mould
• It's hard to develop drugs that destroy viruses because they live and reproduce inside cells
• Drug development


  1. Synthesised in a lab

  2. Chemical extracted from a plant
• Penicillin was discovered by Alexander Fleming
• Drug Testing


  • Toxicity
  • Efficacy
  • Dosage
• Preclinical Testing


  1. Tests on human cells and tissues

  2. Tests on live animals
• Clinical Trials


  1. Tests on healthy volunteers

  2. Tests on ill patients

  3. Finding optimum dose
• Placebo


  Substances that are like the drug being tested but don't do anything
• Clinical trials are often double-blind
• Drugs are often synthesised in a lab, but the process still might start with a chemical extracted from a plant
• It's hard to develop drugs that destroy viruses because they live and reproduce inside cells
• Drug Testing


  1. Toxicity testing

  2. Efficacy testing

  3. Dosage testing
• Preclinical Testing


  • Tests on human cells and tissues
  • Tests on live animals
• Clinical Trials


  • Tests on healthy volunteers
  • Tests on ill patients
  • Finding optimum dose
• Placebos


  Substances that are like the drug being tested but don't do anything
• Clinical trials are often double-blind, with some given the drug and others given the placebo