3.2.4.7 - HIV

Question 1

What does HIV stand for?

Answer 1

Human immunodeficiency virus

Question 2

What does AIDS stand for?

Answer 2

Acquired Immune Deficiency Syndrome

Question 3

Is it possible to catch AIDS? Why?

Answer 3

No. AIDS results from HIV which is contagious

Question 4

When was AIDS first diagnosed?

Answer 4

1981

Question 5

What surrounds the HIV virus?

Answer 5

lipid envelope

Question 6

What structures are embedded within the lipid envelope surrounding the viral cell?

Answer 6

attachment proteins

Question 7

What layer is inside of the lipid envelope on an HIV virus?

Answer 7

capsid

Question 8

What is inside of the capsid on an HIV virus?

Answer 8

RNA and some enzymes

Question 9

What is the enzyme found within the capsid of the HIV virus?

Answer 9

Reverse transcriptase to make DNA from RNA using the host cells organelles.

Question 10

The presence of the enzyme reverse transcriptase means that HIV belongs to which group of viruses?

Answer 10

retroviruses

Question 11

How does HIV get its genetic information into its host cell?

Answer 11

• HIV enters the bloodstream and circulates
• A protein on the HIV binds to CD4 (a protein) found on helper T cells
• the HIV capsid fuses with the hose cell membrane
• the RNA and enzymes move from the HIV virus into the helper T cell
• the HIV reverse transcriptase converts the RNA into DNA.

Question 12

How does HIV replicate in its host cell?

Answer 12

• reverse transcriptase
• uses HIV RNA to make DNA
• DNA joined to host cells DNA
• DNA used to make HIV RNA copies and HIV capsid proteins
• made at host ribosome
• assembly of new virus particles budding off from membrane

Question 13

What happens to the immune system with no helper T cells?

Answer 13

helper T cells are important in cell mediated immunity. Without them B cells and cytotoxic T cells are not stimulated to kill pathogens. This means the body is unable to create an immune response to infection.

Question 14

What are the common secondary infections suffered by HIV patients which often result in death?

Answer 14

infections of the lungs, intestines, brain and eyes, as well as weight loss and diarrhoea.

Question 15

does HIV kill individuals directly?

Answer 15

No. The secondary infections cannot be fought off by the weakened immune system.

Question 16

What does ELISA test stand for?

Answer 16

Enzyme Linked Immunosorbant Assay

Question 17

What does ELISA test for?

Answer 17

Uses antibodies to detect the presence and quantity of a protein in a sample, even if the quantity is very small.

Question 18

How does the ELISA test work?

Answer 18

• apply the sample to a surface to which all the antigens can attach.
• wash the surface to remove unattached antigens.
• add the antibody specific to your antigen and allow them to bind.
• wash the surface to remove unattached antibodies.
• add a second antibody that binds to the first, this antibody is associated with an enzyme.
• add a colourless substrate, which is complementary to the enzyme on the second antibody.
• an enzyme catalysed colour change will occur, the intensity of colour depending on the amount of antigen present.

Question 19

Which diseases is the ELISA test used for?

Answer 19

HIV, TB and Hepatitis

Question 20

Other that detecting diseases, what else is the ELISA test used to detect in the body?

Answer 20

Drug concentration in the body of athletes and other sports men and women.

Question 21

Why are antibiotics ineffective against viruses?

Answer 21

Some antibiotics attack cell walls, which viruses (along with animal cells) to not have.
Cell walls are made from murein which is inelastic so prevents cell expansion when water moves in by osmosis. Antibiotics inhibit the enzymes needed to make cell walls, hence they expand and burst.

Question 22

some tests only detect the presence of HIV antibodies. give 2 reasons why it cannot be used to find out if a person has AIDS?

Answer 22

• need number of helper T cells

- need to be able to identify AIDS related symptoms

Question 23

the solution will remain yellow if a person is not infected with HIV. explain why?

Answer 23

• HIV antibody not present
• will not bind to specific antigen
• 2nd antibody won’t be present

Question 24

a mother who was infected with HIV gave birth to a baby. The baby tested positive using a test. This does not prove the baby is infected with HIV. explain why?

Answer 24

• baby gets antibodies from mother

- so solution will always test positive when first born

Question 25

a control well is set up every time a certain test is used. this is treated in exactly the same way as the test wells, except that blood plasma is replaced by a salt solution.

give 2 purposes of the control well?

Answer 25

• make sure there is no other factor causing colour change

- all antibodies that haven’t been able to bind are washed away

Question 26

human papilloma virus (HPV) is the main cause of cervical cancer. a vaccine has been developed to protect girls and women from HPV.

describe how giving the vaccine leads to production of antibody against HPV?

Answer 26

• vaccine contains antigen from HPV
• displayed on antigen presenting cell
• specific T HELPER cell stimulates specific B cell
• B cell divides by mitosis to form clones to give PLASMA cells
• B cell produces antibody

Question 27

describe how new viruses are produced after HIV has infected a T cell?

Answer 27

• DNA copy of viral DNA made
• inserted into host DNA
• viral proteins made
• makes viral RNA
• hose cell makes new virus
• wrapped in cell membrane