Infection and Response

• There Are Several Types of Pathogen
• Bacteria


  • Very small living cells about 1/100 the size of your body cell, which can reproduce rapidly inside your body
  • They can make you feel ill by producing toxins and poisons that damage your cells and tissues
• Viruses


  • Not cells, they're tiny, about 1/100th the size of a bacterium
  • They can reproduce rapidly inside your body
  • They live inside your cells and replicate themselves using the cells' machinery to produce many copies of themselves
  • The cell will usually then burst, releasing all the new viruses
  • This cell damage is what makes you feel ill
• Protists


  • Single-celled eukaryotes
• Fungi


  • Come in different shapes
• Viral diseases


  • Measles
  • HIV
  • Tobacco Mosaic Virus (TMV)
• Ways pathogens can be spread

  • Direct contact
  • Air
  • Water
• Pathogens can be picked up by touching contaminated surfaces including the skin
• Pathogens can be spread by coughing or sneezing which makes small droplets containing the pathogen become airborne
• Fungal diseases


  • Rose Black Spot
• Rose Black Spot is a fungal disease that causes purple or black spots to develop on the leaves, which can then turn yellow and drop off
• The reduced photosynthesis can mean the plant doesn't grow very well
• The disease can spread through the environment in water or by the wind
• Gardeners can treat the disease using fungicides and by stripping the plant of its affected leaves, which then need to be destroyed
• Malaria is a disease caused by a protist
• Malaria is spread by mosquitoes that feed on infected blood
• Malaria can be treated with antimalarial drugs and prevented by using insecticides and avoiding mosquito bites
• Salmonella and gonorrhoea are two bacterial diseases
• Salmonella


  Bacteria that cause food poisoning
• Gonorrhoea


  A sexually transmitted disease
• Gonorrhoea is caused by bacteria and can be treated with antibiotics
• Destroying vectors, isolating infected individuals, and vaccination can help prevent the spread of communicable diseases
• White blood cells


  • They can consume foreign cells and digest them (phagocytosis)
  • They can produce antibodies that lock onto and help destroy invading pathogens
  • They can produce antitoxins that counteract toxins produced by invading bacteria
• Antibodies


  Specific molecules produced by white blood cells that lock onto and help destroy invading pathogens
• When a person is infected with a pathogen, their body produces antibodies specific to that pathogen, making them naturally immune to future infections by that pathogen
• Vaccination


  Introducing a weakened or dead form of a pathogen to stimulate the immune system to produce antibodies, protecting against future infection
• Vaccination has pros and cons - it protects against future infections but carries a small risk of adverse reactions
• Drugs


  Some just relieve symptoms, others can cure the underlying problem
• Many drugs were originally discovered in plants
• Bacteria can become resistant to antibiotics over time
• Penicillin was the first widely used antibiotic, discovered from a fungus
• It's important to complete a full course of antibiotics to prevent antibiotic resistance developing
• Drug testing


  • Involves three main stages: preclinical testing, clinical trials, and regulatory approval
  • Clinical trials are often double-blind, placebo-controlled studies to ensure objectivity
• The placebo effect can influence the results of drug trials, so it's important to use a placebo control group