B3

• What are pathogens?

  Microorganisms that cause diseases which spread between organisms
• What are the key components of a communicable disease?

  • Pathogen
  • How it's spread
  • Symptoms
  • Prevention/treatment
• What is the pathogen that causes Rose black spot disease?

  • Pathogen: Fungus
  • Spread by: Water and wind
  • Symptoms: Purple/black spots on leaves, yellowing, dropping leaves
  • Prevention: Removing infected leaves, fungicides
• What is the pathogen that causes Malaria?

  • Pathogen: Protist
  • Spread by: Mosquito vectors
  • Symptoms: Fever, can be fatal
  • Prevention: Mosquito nets, stopping mosquito breeding
• What is the pathogen that causes Salmonella food poisoning?

  • Pathogen: Bacterium
  • Spread by: Eating contaminated food
  • Symptoms: Fever, stomach cramps, vomiting, diarrhea, pain when urinating
  • Prevention: Vaccination of poultry, hygienic food preparation
• What is the pathogen that causes Gonorrhoea?

  • Pathogen: Bacterium
  • Spread by: Sexual contact
  • Symptoms: Yellow/green discharge from vagina or penis
  • Prevention: Condoms, antibiotics
• What is the pathogen that causes Measles?

  • Pathogen: Virus
  • Spread by: Airborne droplets (coughs and sneezes)
  • Symptoms: Fever, red skin rash, can be fatal
  • Prevention: Vaccination of children
• What is the pathogen that causes HIV?

  • Pathogen: Virus
  • Spread by: Sexual contact, exchanging bodily fluids (e.g. blood)
  • Symptoms: Flu-like initially, damaged immune system (late stage infection/AIDS)
  • Prevention: Condoms, avoid sharing needles, antiretrovirals
• What is the pathogen that causes Tobacco mosaic virus (TMV)?

  • Pathogen: Virus
  • Spread by: Direct contact between plants
  • Symptoms: Mosaic pattern on leaves, reduces photosynthesis and growth
  • Note: Prevention methods are not required for TMV
• What are the four non-specific defense systems against pathogens?

  1. Skin - acts as a barrier and secretes antimicrobial substances
  2. Mucous membranes - trap pathogens
  3. Cilia - move pathogens out of the respiratory tract
  4. Stomach acid - kills pathogens
• What do antibiotics do?

  They kill bacteria.
• Why is it hard to develop drugs that destroy viruses?

  Because viruses live and reproduce inside cells.
• What are the three things new drugs are tested for?

  1. Toxicity - how harmful the drug is
  2. Efficacy - whether the drug works
  3. Dosage - concentration and frequency of administration
• What is the purpose of clinical trials?

  • Test drugs on healthy volunteers
  • Gradually increase dosage
  • Often double-blind to ensure unbiased results
• Who discovered penicillin?

  Alexander Fleming
• What are monoclonal antibodies?

  • Produced from clones of a single white blood cell (B-lymphocyte)
  • All identical and specific to one protein antigen
• How are monoclonal antibodies produced?

  1. Mouse injected with chosen antigen
  2. B-lymphocytes produce antibodies
  3. B-lymphocyte fused with tumor cell to create hybridoma
  4. Hybridoma divides to produce monoclonal antibodies
• What are three uses of monoclonal antibodies?

  1. Cancer treatment
  2. Locating specific molecules in research
  3. Measuring levels of substances in blood or urine
• What are the six signs of plant disease?

  1. Stunted growth
  2. Spots on leaves
  3. Discolouration
  4. Patches of decay (rot)
  5. Malformed stems or leaves
  6. Abnormal growths (e.g. lumps)
• What are the causes of plant diseases?

  • Infected by pathogens (viruses, bacteria, fungi)
  • Infested by insects (e.g. aphids)
  • Nutrient deficiencies (e.g. nitrate, magnesium)
• What are three ways to identify plant disease?

  1. Look up signs in a gardening manual or website
  2. Take the infected plant to a lab
  3. Use testing kits with monoclonal antibodies
• What are the physical defenses of plants against pathogens?

  • Waxy cuticle on leaves
  • Layers of dead cells around stems
  • Cellulose cell walls
• What are the mechanical defenses of plants against herbivores?

  • Thorns and hairs
  • Leaves that droop or curl
  • Mimicking other organisms
• What are the chemical defenses of plants against pathogens?

  • Antibacterial chemicals
  • Poisons to deter herbivores
• What is nitrate deficiency in plants?

  A condition that stunts growth due to lack of nitrate ions needed for protein synthesis.
• What is magnesium deficiency in plants?

  A condition that causes chlorosis (yellow leaves) due to lack of magnesium ions needed for chlorophyll.