Topic 3 – Infection and Response

• Good Health


  State of mental and physical wellbeing
• Communicable


  Can spread - Infections (caused by pathogens)
• Non-Communicable


  Cannot spread - Cancer, Asthma, CHD (No pathogen)
• Pathogen


  Microorganism that causes disease (foreign antigens on surface)
• Risk Factor


  Increases your chance of getting a disease (e.g. smoking increases chance of lung cancer)
• Non-communicable diseases


  • Costly - Affects themselves and family members, Cost of medicines, Weaker economy (less people working)
• Tumour


  Large ball of cells (2 types: Benign - Less harmful, stays in one place; Malignant - Some cells break off, spreads to different organs, can lead to cancer)
• Cancer survival has improved due to better medicines/treatment and better diagnostic machines for early detection
• Risk factors for cancer

  • Environmental
  • Genetic
  • Smoking
  • UV radiation
  • Viral infection
  • Obesity
• 4 main types of Pathogens

  • Bacteria
  • Virus
  • Protist
  • Fungi
• Bacteria


  Produce toxins that damage cells
• Virus


  Replicate inside host cells, cells burst and cause damage
• Protist


  Single celled eukaryotes, parasites that steal nutrients, spread by vectors e.g. insects
• Fungi


  Have roots called hyphae that penetrate skin/plants and cause disease, spread by spores
• 3 ways pathogens spread

  • Contact with infected surfaces
  • Droplets in the air
  • Contaminated water
• Viral diseases


  • Measles (skin rash, fever)
  • HIV (flu-like symptoms, attacks immune system)
• Fungal diseases


  • Rose black spot (black spots on leaf, reduces photosynthesis)
• Protist diseases


  • Malaria (fever, fatal, spread by mosquito vector)
• How to stop spread of disease

  • Hygiene - wash hands
  • Destroying vectors - chemicals or habitat removal
  • Isolate infected individuals
  • Vaccination - stop it passing on
• Physical barriers


  • Skin
  • Hair, mucus (trap bacteria)
  • Cilia (move mucus up throat)
  • HCl in stomach (kills bacteria)
• White blood cells (WBCs)

  • Phagocytosis (engulf and digest)
  • Antibodies (bind to and destroy pathogens)
  • Antitoxins (remove toxins)
• Vaccines


  1. Dead/inactive pathogen injected into body

  2. WBCs recognise foreign antigen

  3. WBCs turn into memory cells

  4. Memory cells rapidly produce antibodies
• Sources of medicines


  • Plants (chemicals to defend against pests/pathogens)
  • Microorganisms (bacteria produce chemicals to kill other bacteria)
  • Pharmaceutical industry (man-made chemicals)
• Painkillers


  Relieve symptoms (don't kill pathogen)
• Antibiotics


  Destroy bacteria (pathogen) but not viruses (they hide in cells)
• Pros and Cons of vaccines

  • Pros: Control epidemics, Herd immunity
  • Cons: Don't always work, Bad side effects
• Developing resistance


  1. Some bacteria have resistant genes

  2. Antibiotic destroys non-resistant bacteria

  3. Resistant bacteria survive and reproduce

  4. Number of resistant bacteria increase
• How to reduce antibiotic resistance

  • Don't overuse antibiotics
  • Finish the course - stop resistant bacteria from reproducing
• Drug development


  1. Cells/Organs

  2. Small animals (efficacy and toxicity)

  3. Clinical trial: Healthy humans (find optimum dose/side effects)

  4. Blind clinical: Placebo (eliminate psychological effect)

  5. Double blind: Neither doctor/patient know (eliminate bias)
• Monoclonal antibodies


  Identical antibodies that bind to the same antigen
• Making monoclonal antibodies


  1. Fuse B-lymphocyte + Tumour cell to make Hybridoma

  2. Hybridoma makes lots of clones

  3. Extract and purify antibodies from clones
• Uses of monoclonal antibodies

  • Pregnancy test kit
  • Drug delivery to cancer cells
  • Detect presence of hormones/chemicals/molecules in laboratories
• Nitrate


  Amino acids -> Proteins -> Growth
• Magnesium


  Chlorophyll -> Photosynthesis (no chlorophyll = yellow leaves)
• Plant defence mechanisms


  • Physical barriers (waxy cuticle, cellulose wall)
  • Mechanical (thorns, mimicry, droop/curl away)
  • Chemical (antibacterial, poisonous)