biology health and disease triple paper 1

• what cell is destroyed by HIV

  white blood cell
• pathogen = (usually micro) organism that can cause disease
• communicable diseases...

  can be transferred between individuals
• non-communicable diseases...

  cannot be transferred between individuals
• pathogens can be:


  viruses

  bacteria

  fungi

  protists
• health:

  a state of complete physical, mental and social wellbeing
• cholera

  • pathogen: bacteria
  • symptoms: diarrhoea
  • spreads via: contaminated water
• tuberculosis

  • pathogen: bacteria
  • symptoms: cough, lung damage
  • spreads via: airborne
• malaria

  • pathogen: protist
  • symptoms: damage to blood and liver
  • spreads via: animal vector (mosquitos)
• stomach ulcers

  • pathogen: bacteria
  • symptoms: ulcers, pain
  • spreads via: oral transmission (contaminated food)
• ebola

  • pathogen: virus
  • symptoms: haemorraghic(severe bleeding) fever
  • spreads via: bodily fluids
• chalara ash dieback

  • pathogen: fungi
  • symptoms: leaf loss, bark lesions
  • spreads via: airborne
• HIV

  • pathogen: virus
  • symptoms: damages white blood cells
  • spreads via: bodily fluids
• viruses are not living organisms they contain genetic material in a protein coat (caspid)
• although viruses can 'survive' outside of a host cell they need a host cell to reproduce
• lytic pathway:

  1. virus uses proteins and enzymes in host cell to replicate its DNA
  2. these form new viruses
  3. once full of viruses, the cell bursts (lysis)
  4. new viruses go on to infect other cells
• lysogenic pathway:

  1. virus inserts its own genetic material into host cell DNA
  2. as host cell replicates so does the virus
  3. eventually a trigger causes virus to return to lytic pathway
• STIs are spread through sexual contact, sharing needles and blood transfusions
• chlamydia

  bacteria- can reproduce inside host cells

  not always symptoms but can cause infertility
• HIV

  kills white blood cells- which weaken immune system
• the spread of STIs can be reduced by:

  using contraception

  not sharing needles

  abstinence
• physical plant defences against disease

  • waxy cuticle on leaves- barrier to pathogens and pests
  • thick cellulose cell wall- barrier for pathogens that get past the cuticle
• chemical plant defences against disease:

  • producing antiseptics-kill bacteria and fungi
  • (these can be used in drugs for humans)
• identifying disease in plants (observing)

  • browning leaves
  • lesions on bark
  • stunted growth
• human physical barriers to diseases

  • mucus-traps pathogens
  • skin-acts as a barrier
  • cilia- wafts away mucus that contains pathogens to be swallowed and destroyed by stomach acid
• human chemical barriers to disease

  • stomach produces HCl acid-can kill pathogens
  • tears contain enzyme lysozyme that kills bacteria on the eye
• if pathogens enter the body they are killed by the immune system
• B-lymphocytes are a type of white blood cell involved in the specific immune response- the immune response to a specific pathogen
• how B-lymphocytes work

  • every pathogen has unique antigens on its surface
  • B-lymphocytes can produce specific antibodies to the pathogens
  • this means they can be found and destroyed by other white blood cells
  • the antibodies are then produced rapidly and flow around the body to find similar pathogens
• having a low level of white blood cells means you are more suseptible to infections
• chlamydia and HIV are STIs transmitted by sexual contact
• HIV doesn't directly cause illness but attacks the immune system leading to AIDS - this means that your body can't fight off infections
• preventing HIV and chlamydia

  • prevent sexual fluid contact with condoms
  • bottle feeding baby of infected mother
  • not sharing needles when using drugs