HIV

Question 1

Describe the structure of a HIV particle:

Answer 1

1. Lipid envelope.
2. RNA
   3 Reverse transcriptase
3. Capsid
4. Attachment protein

Question 2

Describe the replication of HIV in helper T cells

Answer 2

1. HIV 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 and reverse transcriptase
2. Reverse transcriptase converts viral RNA to DNA
3. Viral DNA inserted / incorporated into helper T cell DNA (may remain latent) 6. Viral protein / capsid / enzymes are produced
   a. DNA transcribed into HIV mRNA
   b. HIV mRNA translated into new HIV proteins
4. Virus particles assembled and released from cell (via budding).

Question 3

Explain how HIV causes the symptoms of acquired immune deficiency syndrome (AIDS):

Answer 3

1. 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
2. Immune system deteriorates → more susceptible to (opportunistic) infections
3. Pathogens reproduce, release toxins and damage cells

Question 4

Explain why antibiotics are ineffective against viruses:

Answer 4

1. Viruses do not have structures / processes that antibiotics inhibit:
2. Viruses do not have metabolic processes (eg. do not make protein) / ribosomes
3. Viruses do not have bacterial enzymes / murein cell wall