B5 , B6 and B7 Disease

• Pathogen


  A disease causing microorganism
• Types of pathogens


  • Bacteria
  • Virus
  • Fungi
  • Protist
• Bacteria


  Produces toxins
• Virus


  Reproduces inside the host cell, and damages the cells
• Fungi


  Often causes growths on the organism
• Protist


  Damages cells
• Bacterial pathogens


  • Gonorrhoea - green discharge from genitals, transmitted through unprotected sex, treated with antibiotics
  • Salmonella - diarrhoea and vomiting, transmitted through contaminated or undercooked food, treated through hydration
  • Crown galls - tumour like growth on plants, transmitted by direct contact, physically remove the gall
• Viral pathogens


  • HIV - immune system is damaged, transmitted through unprotected sex & sharing needles, no cure but treatment to stop HIV from reproducing
  • Measles - spots on skin, fever, transmitted by direct contact, treated with fluids
  • TMV - affects plants, reduced growth & black areas on leaves, transmitted by direct contact & contaminated soil, no treatment
• Fungal pathogens


  • Athletes foot - sore feet, fungal growth on feet, grows in humid conditions, treated using fungicide & frequently washing feet/ clean socks
  • Rose black spot - purple or black spots develop on the leaves, and the leaves drop early, spread by water or wind, treated using fungicides
• Protist pathogen


  • Malaria - fever, can result in death, transmitted by a vector = mosquito, treated with antimalarial drugs, prevent transmission by killing mosquitos/preventing them breed
• How a vaccine works

  1. The person is injected with an inactive form of the pathogen

  2. The white blood cells recognise the antigens on the outside of the pathogen

  3. They make a specific antibody which is complementary to the antigen

  4. The antibody destroys the pathogen

  5. Memory cells stay in the body which can quickly produce an antibody for the pathogen should the person be reinfected with the real pathogen

  6. This means the pathogen is destroyed before the person has any symptoms = immunity
• Viruses reproduce inside the body cells, so an antibiotic would also harm the body cell
• Antibiotic resistance


  When a bacteria can no longer be killed by an antibiotic
• Reasons for increase in antibiotic resistance

  • Prescribing antibiotics too often
  • Use of antibiotics in farming
  • Prescribing antibiotics for mild infections
• How antibiotic resistance evolves

  1. One bacteria has a mutation for resistance

  2. Antibiotics are used and all bacteria who are not resistant are killed. The resistant bacteria survive (survival of the fittest)

  3. The resistant bacteria reproduce

  4. They pass on the gene/DNA for resistance

  5. So the whole population becomes resistant
• Drugs from nature


  • Digitalis - treats heart disease - from foxgloves
  • Penicillin - antibiotic - grown from moulds by Fleming
  • Aspirin - painkiller - from willow bark
• Drug development process


  1. Tested on cells - to test for toxicity (is it safe)

  2. Tested on animals (mice) - to test for toxicity

  3. Tested on a small number of healthy humans in a low dose - test for toxicity

  4. Tested on a small number of humans with the disease - test for dosage (how much do they need to have?) and efficacy (does it work?)

  5. Tested on lots of people with the disease

  6. Approval - results published and peer reviewed
• How the human body helps stop pathogens from entering

  • Skin = barrier
  • Hydrochloric acid in the stomach = kills bacteria
  • Cilia & mucus in the trachea - mucus traps pathogens & cilia moves them away
• How white blood cells help defend against pathogens

  • Produce antibodies = kill pathogen
  • Produce antitoxins = cancel out toxins
  • Engulf pathogens & destroy them
• Communicable disease


  An infectious disease caused by a pathogen
• Non-communicable disease


  A non infectious disease NOT caused by a pathogen (often caused by lifestyle factors)
• Cancer


  Cells dividing uncontrollably form a mass called a tumour. It can be malignant = spreads in the blood OR benign = does not spread
• How cancer can be treated

  • Chemotherapy - chemicals to kill the fast growing cells
  • Radiotherapy - targeted at the tumour to slow growth
• Lifestyle factors that can cause non-communicable diseases

  • Smoking - causes cancers. Tar = carcinogen. Nicotine = raises blood pressure & causes fatty plaques to be made. Carbon monoxide = binds to haemoglobin and causes less oxygen to be carried
  • Drinking excessive alcohol - causes liver disease (cirrhosis of the liver) & cancers & for pregnant women causes deformity in the development of the foetus
  • Being overweight - causes type 2 diabetes and some cancers
  • Eating a diet very high in fats - can cause blocker coronary arteries = heart attacks & strokes
• Effect of smoking and drinking whilst pregnant on the developing foetus

  • Smoking - increases chance of miscarriage, still birth, low birth weight & reduces amount of oxygen reaching the foetus
  • Alcohol - low birth weight, stillbirths, FAS (foetal alcohol syndrome where the child has learning difficulties and developmental difficulties)
• Effect of a fatty diet on the heart

  • Fatty deposits build up in the coronary arteries, this restricts the blood flow so not enough oxygen gets to the muscle of the heart. This is a heart attack and the muscle dies
• Pacemaker


  Found in the right atrium of the heart, controls heart rate (gets all of the muscle cells to beat at the same time)