Chapter 8: Defending against diseases

• Pathogens


  Disease-causing microorganisms
• Types of pathogens


  • Bacteria
  • Viruses
• Bacteria


  • Living cells
  • Multiply rapidly by dividing into a binary fission
• Viruses


  • Not living cells
  • Reproduce inside human cells
• How viruses attack


  1. Enter the cells

  2. Make use of the cell's machinery

  3. Replicate

  4. Release species/poisons

  5. Damage the cell
• Infectious diseases


  Diseases that can be transmitted from one person to another
• Common disease symptoms


  • High body temperatures
  • Headache
  • Rashes
• Ways to prevent infectious diseases

  • Greater use of disinfectants
  • Better cleaning
• Ways pathogens can enter the body

  • Direct contact
  • Contaminated food/drink
  • Through a break in the skin
• Non-specific defense responses


  • Immediate and same for each pathogen
• Specific defense responses


  • Slower and specific to each pathogen
• Phagocytosis


  Phagocytes engulf and ingest pathogens
• Antibody production


  1. B cells produce antibodies that attach to pathogens

  2. Antibodies mark pathogens for destruction by other cells
• Antigens


  Signs on the surface of cells that the immune system recognises
• Antibodies


  Proteins made by the immune system in response to a specific antigen
• If infected with a disease

  The body will fight off the pathogens before symptoms appear next time
• Vaccination


  Introducing weakened or dead pathogens into the body to allow the immune system to recognise and fight them off
• Vaccination reduces the spread and chances of people coming into contact with specific pathogens
• Vaccines


  • MMR (Mumps, Measles, Rubella)
• Antibiotics


  Substances that kill or inhibit the growth of bacteria
• Antibiotics do not kill viruses, protozoa, or fungi
• Antibiotics do not affect human cells
• Painkillers


  Reduce pain but do not kill pathogens
• Antivirals


  Kill viruses but not bacteria
• Mutations of pathogens can make them more resistant to antibiotics/antivirals
• Resistant strains can spread rapidly as people are unvaccinated and antibiotics/antivirals aren't as effective
• To prevent antibiotic resistance, don't use antibiotics when not needed and use them correctly
• Growing and investigating bacteria - Practical

  1. Use aseptic techniques

  2. Sterilise equipment

  3. Work near a Bunsen burner

  4. Avoid air-tight seals

  5. Incubate at 25°C or below
• Microorganisms from practical may harm the immune system
• Disinfect benchtop with alcohol and use heat to sterilise equipment
• Work near a Bunsen burner to prevent contamination
• Avoid making air-tight seals on dishes to prevent excessive growth
• Incubate at 25°C or below to prevent culturing harmful pathogens