5. HIV and Viruses

Question 1

HIV

Answer 1

human immunodeficeny virus
affects immune system
leads to AIDS (acquired immune deficiency syndrome)

Question 2

AIDS

Answer 2

immune system deteriorates and eventually fails - vulnerable to infection

Question 3

how does HIV work

Answer 3

infects (eventually killing) helper T cells (host cell)
helper t cells send chemical signals that activate phagocytes, cytotoxic T-cells, B-cells
without these cant form effective response to infections

Question 4

how do people with HIV develop AIDS

Answer 4

helper T cell numbers critically low level

Question 5

how HIV replicates

Answer 5

1. attachment protein attaches to receptor on membrane of host helper T cell
2. capsid released into cell. uncoats releasing genetic material (RNA) into cytoplasm
3. reverse transcriptase makes complimentary strand of DNA from viral RNA template
4. double stranded DNA is made and inserted into human DNA
5. host cell enzymes now used to make viral proteins from viral DNA
6. viral proteins assemble into new virus -> bud from cell and infect other cells

Question 6

symptoms of AIDS

Answer 6

1. minor infections
2. immune system cells decrease -> more serious infections
3. very low number of immune system cells -> range of serious infections

Question 7

things that affect survival of AIDS

Answer 7

existing infections
strain of HIV
access to healthcare

Question 8

why don’t antibiotics work against viruses

Answer 8

1. kill bacteria by interfering with metabolic reactions (enzymes, ribosomes)
2. bacterial enzymes etc different from human enzymes. antibiotics only target bacterial ones
3. viruses don’t have own enzymes and ribosomes (use the host cells) antibiotic cant inhibit.

Question 9

antiviral drugs

Answer 9

target virus specific enzymes e.g. HIV uses reverse transcriptase human cells dont
drugs can be designed to inhibit without affecting cell

Question 10

cure for HIV?

Answer 10

no cure / vaccine

antiviral drugs used to slow down progression

Question 11

how is HIV spread

Answer 11

unprotected sex
infected bodily fluids (contaminated needle)
mother to fetus