HIV

• Describe the structure of a HIV particle

  Lipid envelope

  RNA

  reverse transcriptase

  capsid

  attachment protein
• Describe the replication of HIV in helper T cells

  1 Attachment proteins attach to receptors on helper T cell

  2 Lipid envelope fuses with cell-surface membrane, releasing capsid into cell

  3 Capsid uncoats, releasing RNA + reverse transcriptase

  4 Reverse transcriptase converts viral RNA to DNA

  5 Viral DNA inserted into helper T cell DNA

  6 Viral protein / capsid / enzymes are produced:

  a DNA transcribed into HIV mRNA

  b. HIV mRNA translated into new HIV proteins

  7 Virus particles assembled + released from cell
• Explain how HIV causes the symptoms of acquired immune deficiency syndrome (AIDS)

  ● HIV infects and kills helper T cells (host cell) as it multiplies rapidly

  ○ So T helper cells can’t stimulate cytotoxic T cells, B cells and phagocytes

  ○ So B plasma cells can’t release as many antibodies for agglutination & destruction of pathogens

  ● Immune system deteriorates → more susceptible to (opportunistic) infections

  ● Pathogens reproduce, release toxins and damage cells
• Explain why antibiotics are ineffective against viruses

  Viruses do not have structures / processes that antibiotics inhibit:

  ● Viruses do not have metabolic processes (eg. do not make protein) / ribosomes

  ● Viruses do not have bacterial enzymes / murein cell wall