HIV Flashcards
1
Q
Describe the replication of HIV in helper T cells
A
- HIV infects T helper cells - HIV attachment protein attaches to a receptor on the helper T-cell membrane
- Virus lipid envelope fuses with cell surface membrane and capsid released into cell which uncoats, releasing RNA and reverse transcriptase into cytoplasm
- Viral DNA is made from viral RNA - Reverse transcriptase produces a complementary viral DNA strand from viral RNA template
- Double stranded DNA is made from this (DNA polymerase) - Viral DNA integrated into host cell’s DNA (by enzyme integrase)
- This remains latent for a long time in host cell until activated
- Host cell enzymes used to make viral proteins from viral DNA (within human DNA) → viral proteins assembled with viral RNA to make a new virus
- New virus bud from cell (taking some of cell surface membrane as envelope)
- Eventually kills helper T cells
- Most host cells are infected and process repeat
2
Q
Explain how HIV causes the symptoms of AIDS –
acquired immune deficiency syndrome
A
- Infects and kills helper T cells (host cell) as it multiplies rapidly
- T helper cells then can’t stimulate cytotoxic T cells, B cells and
phagocytes → impaired immune response - E.g. B plasma cells can’t secrete antibodies for agglutination and
destruction of pathogens by phagocytosis - Immune system deteriorates
- More susceptible to infections
- Diseases that wouldn’t cause serious problems in healthy
immune system are deadly
3
Q
Explain why antibiotics are ineffective against viruses
A
- Antibiotics can’t enter human calls – but viruses exists in its host
cell (they are acellular) - Viruses don’t have own metabolic reactions e.g. ribosomes (use
of the host cell’s) which antibiotics target - If we did use them… act as a selection pressure + gene mutation
= resistant strain of bacteria via natural selection → reducing
effectiveness of antibiotics and waste money
4
Q
Structure of HIV virus
A
Use acronym CARRL
C= Capsid
A=Attachment protein
R=RNA
R=Reverse transcriptase
L=Lipid envelope
