the immune system (HIV)

Question 1

what does HIV stand for?

Answer 1

human immunodeficiency virus

Question 2

what is HIV?

Answer 2

virus that affects the immune system

Question 3

what does HIV eventually lead to?

Answer 3

AIDS

Question 4

what does AIDS stand for?

Answer 4

acquired immune deficiency syndrome

Question 5

what is AIDS?

Answer 5

condition where the immune system deteriorates and eventually fails
makes someone more vulnerable to other infection

Question 6

when do people with HIV develop AIDS?

Answer 6

when T helper cell numbers reach a critically low level

Question 7

what does HIV do?

Answer 7

infects T helper cells, which act as host cells for the virus
immune system cannot offer an effective response

Question 8

what is the structure of HIV?

Answer 8

core= contains genetic material (RNA) and some proteins
capsid= protein coat
envelope= lipid membrane stolen from the cell membrane of a previous host cell
attachment proteins= help HIV attach to the host T helper cell

Question 9

what enzymes are present in HIV?

Answer 9

reverse transcriptase, integrase, protease

Question 10

what is the role of reverse transcriptase?

Answer 10

catalyses the use of viral RNA to form viral DNA by reverse transcription

Question 11

what is the role of integrase?

Answer 11

catalyses the integration of the viral DNA into the genome of the host cell

Question 12

what is the role of protease?

Answer 12

catalyses the break up of large polypeptides into smaller pieces- essential in assembling new viral particles

Question 13

how do antiviral drugs work?

Answer 13

target specific enzymes, such as reverse transcriptase

Question 14

when do people with HIV develop symptoms?

Answer 14

during the initial period HIV rapidly replicates
the infected person develops flu like symptoms
after replication decreases this is known as the latency period
during this time people don’t get symptoms

Question 15

why don’t antibiotics work against viruses?

Answer 15

antibiotics kill bacteria by interfering with their metabolic reactions
viruses do not have their own enzymes/ribosomes, so use host cells
antibiotics cannot inhibit because they only target bacterial cells not human cells

Question 16

how can HIV spread?

Answer 16

unprotected sexual intercourse
infected body fluids
passed onto a positive mother to the foetus

Question 17

how does HIV infect host cells?

Answer 17

1) HIV binds to the CD4 receptor on T helper cells
2) viral and cellular membranes fuse
3) HIV virion penetrates the CD4 receptor membrane and enters the host cell
4) capsid is injected into the cytoplasm of the T Helper cell
5) capsid dissolves in a process called uncoating, which releases viral RNA
6) reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template
7) double stranded DNA is made and inserted into human DNA (categorised by intergrase)
8) viral RNA is transported out of the nucleus into HIV subunits and genetic material for new viruses
9) protease breaks polyproteins to make virions
10) in budding, virions are released out of the cell into circulation to infect other cells