HIV

Question 1

What is the structure of HIV?

Answer 1

• Outside has a lipid envelope
• Attachment proteins embedded in the lipid envelope.
• Inside the envelope is a protein layer called the capsid.
• Two single strands of RNA and enzymes is inside the capsid.

Question 2

What is the enzyme present in HIV?

Answer 2

Reverse transcriptase.

Question 3

What does reverse transcriptase do?

Answer 3

Makes DNA from RNA.

Question 4

What type of virus is HIV?

Answer 4

Retrovirus

Question 5

How does HIV replicate?

Answer 5

• HIV enters the blood stream and circulates around the body.
• Protein on the HIV binds to a protein called CD4, this protein occurs on helper T cells.
• Protein capsid fuses with the cell surface membrane, the RNA and enzymes of HIV enter the helper T cell.
• HIV reverse transcriptase converts the virus’ RNA into DNA.
• Newly made DNA is moved into the helper T cell’s nucleus, where it is inserted into the cell’s DNA
• HIV DNA in the nucleus creates messenger RNA using the cell’s enzymes. The mRNA contains the instructions for making new viral proteins and the RNA to go into the new HIV.
• mRNA passes out of the nucleus through a nuclear pore and uses the cell’s protein synthesis mechanisms to make the HIV particles
• HIV particles break away from the helper T cell with a piece of it’s cell surface membrane surrounding them which forms their lipid envelope.

Question 6

How does HIV cause aids?

Answer 6

• HIV causes AIDS by killing or interfering with the normal functioning of helper T cells.
• Helper T cells are important in cell immunity, without a sufficient number of helper T cells, the immune system cannot stimulate B cells to produce antibodies, or cytotoxic T cells that kill cells infected by pathogens.
• Memory cells are also infected and destroyed.
• The body is no longer able to produce an adequate immune response and becomes susceptible to infections and cancers.

Question 7

What happens the helper T cell count while infected with AIDS?

Answer 7

They reach a critically low level.

Question 8

What are the initial symptoms of AIDS?

Answer 8

• Minor infections of mucous membranes

* recurring respiratory infections.

Question 9

What are the mid stage symptoms of AIDS?

Answer 9

• Number of immune system cells decreases further

* More susceptible to serious infection.

Question 10

What are some late stage symptoms of AIDS?

Answer 10

• Very low number of immune system cells.
• Range of serious infections are developed.
• These serious infections can lead to death.

Question 11

What does ELISA stand for?

Answer 11

Enzyme linked immunosorbant assay

Question 12

What does the ELISA test do?

Answer 12

Uses antibodies to detect the presence and quantity of a protein in sample

Question 13

How is the ELISA test used to detect HIV?

Answer 13

• HIV antigen is bound to the bottom of a well in a well plate
• A sample of the patient’s blood plasma is added to the well, if there are any HIV specific antibodies, they will bind to the HIV antigen stuck to the bottom of the well.
• Well washed out to remove unbound antibodies.
• Secondary antibody, which has a specific enzyme attached to it, is added to the well, the secondary antibody can bind to the HIV specific antibody.
• Well is washed out to remove any unbound secondary antibody, if there is no primary antibody, all of the secondary antibody is washed away.
• A solution is added to the well, solution contains a substrate which is able to react with the enzyme attached to the secondary antibody and produce a coloured product. if the solution changes colour, it indicates that the patient has HIV specific antibodies in their blood and is infected with HIV.

Question 14

What do antibiotics do?

Answer 14

Kill bacteria by interfering with their metabolic reactions, they target bacterial enzymes and ribosomes in these reactions.

Question 15

Why are antibiotics effective?

Answer 15

• Bacterial enzymes and ribosomes are different from human enzymes and ribosomes.
• Antibiotics only target bacterial ones, so that they do not damage human cells.

Question 16

Why are antibiotics not effective against viruses?

Answer 16

• Viruses don’t have their own enzymes and ribosomes, they use the host’s cells.
• This means that antibiotics are not effective, because they do not target human processes.

Question 17

How do antiviral drugs work?

Answer 17

• They target the few virus specific enzymes that exist, for example reverse transcriptase of HIV.
• Humans do not use these enzymes, so drugs are able to inhibit it without affecting the host cell.