1. Go to this link and complete questions 1 +2 only!
SPECIFICATION POINTS:
Structure of the human immunodeficienc y virus (HIV) and its replication in helper T cells.
How HIV causes the symptoms of AIDS.
Why antibiotics are ineffective against viruses.
The use of antibodies in the ELISA test.
Go to this link and complete questions 1 +2 only!

2. ELISA – detecting HIV Enzyme Linked Immuno-sorbant Assay/
SPECIFICATION POINTS:
Structure of the human immunodeficienc y virus (HIV) and its replication in helper T cells.
How HIV causes the symptoms of AIDS.
Why antibiotics are ineffective against viruses.
The use of antibodies in the ELISA test.
ELISA – detecting HIV
Enzyme Linked Immuno-sorbant Assay/
Can help you detect the presence of antigens and how many antigens.

3. Direct ELISA A test to detect the presence of HIV antigens
4. Finally substrate is added and only will be broken down by the enzyme on bound antibodies. If there is a colour change, this is a positive result for HIV
An antibody that is complimentary to the HIV/pathogen antigen is attached to the glass dish.
3. A secondary antibody is added, this one is complimentary to the HIV antigen too but on an alternative site. These either become fixed if HIV antigen present or washed away if not. This secondary antibody is bound to an enzyme that can cause a change in colour if substrate is added.
2. The sample from a person (usually blood or urine) is added to the dish.
If the person has the HIV antigen (hence has been infected), then they will attach to the antibody and become fixed.
Any unbound antigens/fluids are washed away.

4. Indirect ELISA A test to detect the presence of HIV antibodies
The HIV/pathogen antigen is attached to the glass dish.
The sample from a person (usually blood or urine) is added to the dish.
If the person has HIV antibodies (hence has been infected), then they will attach to the antigen and become fixed.
Any unbound antibodies/fluids are washed away.
A secondary antibody is added, this one is complimentary to the HIV antibody that could be present in the body fluid. These either become fixed if HIV antibody present or washed away if not. This secondary antibody is bound to an enzyme that can cause a change in colour if substrate is added.
Finally substrate is added and only will be broken down by the enzyme on bound antibodies. If there is a colour change, this is a positive result for HIV

5. SPECIFICATION POINTS:
Structure of the human immunodeficienc y virus (HIV) and its replication in helper T cells.
How HIV causes the symptoms of AIDS.
Why antibiotics are ineffective against viruses.
The use of antibodies in the ELISA test.

6. SPECIFICATION POINTS:
Structure of the human immunodeficienc y virus (HIV) and its replication in helper T cells.
How HIV causes the symptoms of AIDS.
Why antibiotics are ineffective against viruses.
The use of antibodies in the ELISA test.
How could an ELISA test also become quantitative (i.e. indicate the amount of antigen in the blood)