HIV

Question 1

structure of HIV

Answer 1

• lipid envelope
• attachment proteins
• capsid (made of protein, protects viral RNA)
• two strands of RNA
• enzyme reverse transcriptase

Question 2

replication of HIV

Answer 2

1) Attachment proteins bind to a protein CD4 on helper T-cells
2) Capsid fuses with the cell membrane, RNA and enzymes are released
3) reverse transcriptase converts RNA into double-stranded cDNA
4) DNA is moved into the nucleus, inserted into host cell’s DNA
5) mRNA created using cell’s enzymes, leaves the nucleus
6) HIV particles made using cell’s protein synthesis
7) break away from the cell using some of its cell-membrane to form the lipid envelope

Question 3

Why is HIV a retrovirus?

Answer 3

uses RNA to synthesise DNA

Question 4

how HIV causes symptoms of aids

Answer 4

• damages helper T-cells
• can’t stimulate B cells to produce antibodies or cytotoxic T-cells to kill infected cells
• allows secondary infections to occur

AIDS - acquired immunodeficiency syndrome

Question 5

treating HIV

Answer 5

• attachment and entry inhibitors - prevents attachment of HIV to T-helper cells
• reverse transcriptase inhibitors - prevents formation of viral cDNA
• integrate inhibitors - prevents integration of viral DNA into host cell’s DNA
• protease inhibitors - prevents modification of HIV proteins

Question 6

why antibiotics are ineffective against HIV

Answer 6

• antibiotics work by disrupting metabolic processes, but viruses don’t have their own, they rely on host cells for cell structures and metabolic processes
• viruses have a protein coat instead of a murein cell wall so there’s no site for antibiotics to work
• antibiotics cannot reach the viruses inside the host cells