Cells - Cell recognition and the immune system - 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

• the HIV reverse transcriptase converts the RNA into DNA.
• the new DNA moves into the hose cells nucleus and incorporates into the genetic material.
• protein synthesis occurs and the DNA is used to create mRNA.
• the mRNA passes out of the nuclear pore and undergoes protein synthesis to make new viral proteins.
• the new HIV viral cells break away from the helper T cells with a piece of the membrane around them to form their lipid envelope.

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.