biology topic 5

• Health


  A state of complete physical, mental and social well-being (WHO)
• Disease


  A condition where part of an organism doesn't function properly
• Types of disease


  • Communicable
  • Non-communicable
• Communicable disease


  A disease that is passed directly between individuals, caused by a pathogen
• Pathogen


  Organisms such as viruses, bacteria that cause communicable diseases
• Non-communicable disease


  A disease that cannot be transmitted between individuals
• Symptom


  A change experienced by an organism that indicates disease
• Having an illness


  Makes an individual more likely to contract another disease (weakens the immune system)
• Cholera: Pathogen, symptoms, how it spreads, how to reduce spread


  • Caused by Vibrio cholerae bacterium,
  • Diarrhoea
  • Contaminated water
  • making sure people have clean water
• Tuberculosis (TB): Pathogen, Symptoms, How its spread, How to reduce spread


  • Caused by Mycobacterium tuberculosis bacterium,
  • Coughing and lung damage
  • Airborne when people cough
  • Infected people should avoid crowded public spaces, have ventilated homes
• Chalara ash dieback: pathogen,symptoms, how it spreads, how to reduce spread


  • Caused by a fungus that infects ash trees,
  • Leaf loss and bark lesions (wounds)
  • spread via airborne spores which are carried by the wind
  • Removing young infected ash trees and replanting with a different species
• Malaria: Pathogen, symptoms, how it spreads, how to reduce spread


  • Caused by a protist,
  • Damage to red blood cells
  • spread by mosquito vectors which pick up the protist when feeding on the blood of an infected organism and transmit malaria to other organisms,
  • Mosquito nets and insect repellent
• Stomach ulcers : pathogen, symptoms, how its spread, how to reduce spread


  • Caused by Helicobacter pylori bacterium,
  • Stomach pain, vomitting
  • transmitted orally by eating infected foods or drinking infected water
  • Having clean water supplies
• Ebola : pathogens, symptoms , how its spread, how to reduce spread


  • Caused by Ebola virus,
  • fever with bleeding
  • via bodily fluid
  • Isolating infected individuals and sterilising infected areas
• How viruses cause disease (biology only)


  They enter host cells and replicate inside of them. The host cells rupture, releasing new viruses.
• Viruses vs other microorganisms (biology only)

  Viruses are not living organisms. They do not reproduce and can only replicate inside a host cell.
• Pathways for virus replication inside living cells (biology only)


  • Lytic pathway
  • Lysogenic pathway
• Lytic pathway (biology only)


  1.Virus binds to specific receptors on host cell and injects its DNA into host cell

  2.replicates its DNA using host cells proteins and enzymes

  3. New viral structures are produced and assembled

  4. Host cell ruptures, releasing new viruses which infect more cells
• Lysogenic pathway (biology only)

  1.Virus binds to specific receptors on host cell and injects DNA

  2. The viral DNA becomes integrated into host cell DNA

  3. Each time the host cell replicates as usual, the viral DNA also replicates but remains inactive

  4. Trigger (eg a chemical) causes the viral DNA to leave the genome and enter the lytic pathway( at stage 2)
• HIV(5)


  • Human immunodeficiency virus kills white blood cells which are important in the immune response
  • Hiv eventually leads to AIDS
  • This is when infected persons immune system deteriorates and fails
  • Person becomes susceptible to other pathogens
  • HIV is spread via infected bodily fluids
• Reducing the spread of HIV


  1. Use of condoms and protected sex

  2. Needle exchange

  3. Screening blood for HIV

  4. Deterring infected mothers from breastfeeding
• Chlamydia(2)


  • Bacterium that can only reproduce inside host cells
  • Can result in infertility in men and women
• Reducing the transmission of Chlamydia

  1. Use of condoms and protected sex

  2. Screening