b3

• Pathogens


  Microorganisms that cause infectious diseases
• Types of pathogens


  • Bacteria
  • Viruses
  • Protists
  • Fungi
• Bacteria

  • Very small cells
  • Can reproduce rapidly inside the body
  • Produce toxins that damage cells
• Viruses

  • Captured rapidly
  • Live and produce inside cells
  • Cause damage when they burst cells
• Protists

  • Single-celled eukaryotes
  • Some are parasites that can damage host organisms
• Fungi

  • Single-celled or have a body made up of hyphae
  • Hyphae can grow and penetrate human skin and surfaces of plants
  • Produce spores that can spread
• Pathogens can spread by direct contact, water or air
• Vectors don't get the disease but can spread it
• Viral diseases


  • Measles
  • HIV
• Bacterial diseases


  • Salmonella food poisoning
  • Gonorrhoea
• Fungal diseases


  • Rose black spot
• Protist diseases


  • Malaria
• Human defence systems


  • Skin as a barrier
  • Nose hair and mucus trapping particles
  • Trachea and bronchi secreting mucus
  • Stomach producing hydrochloric acid
• Preventing disease spread


  1. Using insecticides on vectors

  2. Isolating infected individuals

  3. Vaccination
• Immune system


  • White blood cells patrolling for microbes
  • Phagocytes engulfing and digesting foreign cells
  • Producing antibodies to target specific antigens
• Vaccination


  Introducing small quantities of dead or inactive form of a pathogen to stimulate the immune system to produce antibodies
• Vaccinations can protect from future infection
• Vaccinations don't always work and can have bad reactions, but these are rare
• Antibiotics


  Medicines that kill bacteria
• Antibiotics cannot treat viral pathogens
• Overuse of antibiotics has led to the emergence of resistant strains
• It's important to finish a full course of antibiotics to prevent still being infected and causing bacteria to reproduce
• Developing new drugs


  1. Preclinical testing on human cells in a lab

  2. Preclinical testing on animals

  3. Clinical trials on healthy human volunteers

  4. Clinical trials on patients with the disease
• New drugs must be extensively tested for toxicity and efficacy
• Drugs are often derived from natural sources like plants
• Clinical trials are often double-blind, where neither the patient nor the doctor knows who is receiving the drug or placebo
• Drug trial results are not published until they have been peer-reviewed