HIV

Question 1

what is HIV?

Answer 1

• Human Immunodeficiency Virus
• retrovirus that attacks bodys immune system

Question 2

what is AIDS?

Answer 2

condition where the immune system deteriorates and fails

Question 3

describe how HIV replicates?

Answer 3

1) attachment protein on HIV attatches to CD4 on surface of helper t cells
- HIV lipid envelope fuses with cell emmbrane

2) capsid passes into cell + release RNA and reverse transcriptase

3) reverse transcriptase converts viral RNA into double stranded DNA
- DNA now moves into cell nucleus and integrates with host DNA

4) HIV RNA and proteins made at host ribosomes

5) virus particles assembled which bud off from cell membrane and go on to infect other cells

Question 4

how is HIV transmitted?

Answer 4

unprotected sex with an infected person

transmission of infected persons bodily fluids (e.g. blood)

from mother to child
- shared through placenta
- transmission through breast milk

Question 5

what happens during late stages of AIDS

Answer 5

• patients have very low number of immue system cells
• can develop several serious infections

these infections kill people not the HIV

Question 6

why can’t antibiotics be used on viruses?

Answer 6

• antibiotics kill bacteria by interfering with their metabolic reactions
• antibiotics designed to target bacterial structures eg. cell wall and ribosomes
• viruses dont have their own cell wall and ribosomes
• so antibiotics cant inhibit them

Question 7

how do antiviral drugs work?

Answer 7

• inhibit the enzyme reverse transcriptase
• stopping the virus from replicating

Question 8

explain how a mutation can result in a non functional protein?

Answer 8

• changes the amino acid sequence
• changes the position of hydrogen/ionic/disulfide bonds
• changes the tertiary structure

Question 9

how do people with HIV develop AIDS?

why does aids end up killing people

Answer 9

• HIV replicates inside of t helper cells, destorying them
• Number of helper T cells reaches a critically low level
• T helper cells no longer stimulate B cells
• so no antibodies released
• immune system no longer able to fight against infections

Question 10

what happens in the ELISA test?

used for detecting HIV

Answer 10

1) HIIV antigen bound to bottom of well in well plate
2) patients blood plasma is added to the well
3) 3) any HIV specific antibodies will bind to HIV antigens
4) plate is washed (to remove any unbound antibodies)
5) a secondary antibody with an enzyme attatched is added
6) this secondary antibody binds to HIV specific antibody - antigen complex (secondary antibody is specific to first antibody added, so binds to that)
7) the plate is washed - to remove any unbound antibodies
8) a solution is added containing substrate
- reacts with enzyme and produces colour change
9) colour change = positive HIV result

Question 11

what are the structures of HIV?

Answer 11

1) RNA
- two single strands
2) reverse transcriptase
- converts RNA into DNA
3) capsid
layer of protein molecules that surrounds and protects genetic material
4) viral envelope
- outer layer made up of phospholipids
5) attachment proteins
-help virus bind to host cell