HIV

• describe how HIV replicates

  HIV binds to CD4 receptor on T helper cells

  the HIV capsid is released inside the cell

  viral RNA is converted into DNA by reverse transcriptase

  viral dna integrated into host dna

  virus takes over cells ribosomes and cell produces only viral proteins

  viral proteins are released - taking a portion of the phospholipid bilayer to form the viral coat
• describe the structure of HIV

  • Has a lipid envelope with embedded attachment proteins
  • Viral capsid contains RNA and enzymes including reverse transcriptase which produces DNA from RNA
• describe how HIV leads to symptoms of AIDS

  • When an HIV virus infects a TH cell and replicates, the cells are killed.
  • As HIV spreads through the body and more TH cells are killed, the immune system weakens.
  • The weak immune system makes the individual highly susceptible to infection by other pathogens. This is AIDs.
• describe how the ELISA test works

  1. apply sample to slide, antigens will attach
  2. wash surface to remove unbound antigens
  3. add antibody specific to antigen and leave the two to bind
  4. wash again to remove excess antibody
  5. add second antibody with enzyme bound to it to bind to first antibody
  6. add coloured substrate of the enzyme - enzyme acts on the substrate to change into coloured product
  7. Amount of antigen present is relative to the intensity of the colour that develops