b3 disease

• Dilute


  High concentration of water, low concentration of something else
• Concentrated


  Low concentration of water, high concentration of something else
• Bacteria


  Make us ill by producing poisonous chemicals called TOXINS
• Viruses


  Make us ill by reproducing inside cells and causing damage which leads the cell to burst (lysis)
• Bacteria and viruses reproduce very rapidly inside the body, number of pathogens increase very quickly
• Communicable (Infectious) Diseases


  • HIV
  • Flu
  • Chicken Pox
  • Measles
• Non-communicable Diseases


  • Asthma
  • Cancer
  • Diabetes
  • Heart Attack
• Types of Microbes


  • Bacteria
  • Virus
  • Fungi
  • Protists
• Infectious Diseases can be spread by: Air, Direct Contact and Contaminated water
• Pathogens


  Microbes that can cause disease
• Measles


  1. Caused by a virus

  2. Spread by inhalation of droplets released by coughs and sneezes

  3. Symptoms are: red skin rash, fever, can be fatal

  4. Prevention: vaccinate young children
• HIV


  1. Caused by a virus

  2. Spread by direct contact via sexual contact or exchange of bodily fluids

  3. Symptoms: Flu-like illness; leads to AIDS when the immune system can no longer protect against other infections or cancers

  4. Treatment: Anti-retroviral drugs to control the virus
• Tobacco Mosaic Virus


  1. Caused by a virus

  2. Transferred between plants e.g. on gardeners' hands

  3. Affects tomatoes

  4. Symptoms mosaic pattern of discolouration on the leaves, affects growth due to lack of photosynthesis

  5. Prevention: remove affected plant, wash hands, sterilise tools
• Salmonella


  1. Caused by bacteria

  2. Spread by eating contaminated raw food

  3. Symptoms: fever, vomiting, diarrhoea

  4. Prevention: vaccination of chickens, cooking properly, washing hands
• Gonorrhoea


  1. Caused by bacteria

  2. Spread by direct contact via sexual contact (STD)

  3. Symptoms: Thick yellow/green discharge from the vagina or penis; pain when urinating

  4. Treatment: Antibiotics, Penicillin

  5. Prevention: Condoms, barrier methods
• Rose Black Spot


  1. Caused by a fungus

  2. Spread by wind or water

  3. Symptoms: purple or black spots on leaves, turn yellow; poor growth reduced photosynthesis

  4. Treatments: Fungicides, remove and destroy leaves by burning
• Malaria


  1. Caused by a protist

  2. Spread via mosquitoes that act as vectors when they bite to feed on blood

  3. Symptoms: fever, can be fatal

  4. Prevention: prevent mosquitoes from breeding, mosquito nets
• Immune System


  • Recognises and responds to pathogens and destroys them
  • The most important cells are white blood cells, which recognise micro-organisms that shouldn't be in our bodies and destroy them
• Non-Specific Defences


  1. Skin forms a barrier, produces anti-microbial chemicals

  2. Nose contains hairs that trap dust, which may contain pathogens

  3. Trachea + Bronchi produce mucus, which traps microbes

  4. Stomach contains acid which kills microbes
• Specific Defences


  1. White blood cells produce antibodies, which attach to pathogens and destroy them

  2. The antibody has a complementary shape to the antigen
• Phagocytosis


  White blood cells engulf pathogens and destroy them
• Antibodies


  Produced by white blood cells, counteract toxins and stop them from working
• Painkillers reduce the feeling of pain, but do not treat the cause and do not kill pathogens
• Antibiotics kill bacteria but do not kill viruses, protists or fungi
• Problems with antibiotics


  • They don't kill viruses
  • Can't be used to treat viral diseases
  • Overuse of antibiotics leads to antibiotic resistance
  • Difficult to identify the correct antibiotic to use
• Vaccination


  1. Protects against diseases and makes us immune

  2. A dead/inactive version of the pathogen is injected into the body

  3. White blood cells produce the correct antibody, which destroys the pathogen

  4. If infected again, the white blood cells recognize it and make the correct antibodies faster, destroying the pathogen quickly so you don't get ill

  5. Reduces the spread of the disease and leads to herd immunity
• Drug Testing

  1. New drugs are tested for toxicity (is it safe?) and efficacy (does it work?)

  2. Clinical trials: small group of humans (volunteers), blind trial (large group, 50% given drug, 50% placebo), double blind trial (doctor doesn't know who had placebo)

  3. Peer review: independent scientists check the results to prevent false results

  4. Placebo: identical to drug but contains no active ingredients, used to compare the effect of the drug with no drug