As biology help i am so dumb :-:

Describe the role of antibodies in producing a positive test in an ELISA test (4 marks)

All i've done so far is :

- The ELISA test uses antibodies to detect the presence of proteins but also the specific quantity of them (I'm guessing this is 1/4 marks)

what else should i write?

Reply 1

username5442900

13

Original post by Maxistan YT

Describe the role of antibodies in producing a positive test in an ELISA test (4 marks)

All i've done so far is :

- The ELISA test uses antibodies to detect the presence of proteins but also the specific quantity of them (I'm guessing this is 1/4 marks)

what else should i write?

I remember doing this question in the past :/
So here are the four main points you should include (feel free to cut any unimportant bits)

1. HIV antigen is bound to the bottom of a well

2. A sample of the patient's blood plasma is added to the well. lf there are any antibodies specific to HIV, these will bind to the HIV antigen stuck to the bottom of the well. The well is then washed out to remove any unbound antibodies.

3. A secondary antibody that has a specific enzyme attached to it, is added to the well. This secondary antibody can bind to the antibodies specific to HIV (which is also called the primary antibody). The well is washed out again tơ remove any unbound secondary antibody. If there's no primary antibody in the sample, all of the secondary antibody will be washed away.

4. A solution is added to the well. If the solution changes colour, it means that the patient has HIV-specific antibodies in their blood and is infected with HIV, which would indicate a positive result

Reply 2

damsellinstress

16

Memorise your CGP book and mark scheme xx Keep reading over until you have learnt it by heart xx

Reply 3

Maxistan YT

OP

14

Original post by damsellinstress

Memorise your CGP book and mark scheme xx Keep reading over until you have learnt it by heart xx

<3

Reply 4

Jpw1097

19

Original post by damsellinstress

Memorise your CGP book and mark scheme xx Keep reading over until you have learnt it by heart xx

I would argue that you should avoid rote learning where possible. Instead, try to understand the principles and work out the answer.

Reply 5

Jpw1097

19

Original post by DSKE010

I remember doing this question in the past :/
So here are the four main points you should include (feel free to cut any unimportant bits)

1. HIV antigen is bound to the bottom of a well

2. A sample of the patient's blood plasma is added to the well. lf there are any antibodies specific to HIV, these will bind to the HIV antigen stuck to the bottom of the well. The well is then washed out to remove any unbound antibodies.

3. A secondary antibody that has a specific enzyme attached to it, is added to the well. This secondary antibody can bind to the antibodies specific to HIV (which is also called the primary antibody). The well is washed out again tơ remove any unbound secondary antibody. If there's no primary antibody in the sample, all of the secondary antibody will be washed away.

4. A solution is added to the well. If the solution changes colour, it means that the patient has HIV-specific antibodies in their blood and is infected with HIV, which would indicate a positive result

This answer has mentioned how ELISAs can detect a particular antibody qualitatively (I.e. that the antibody is present or not) but has not mentioned how ELISAs can be used to quantify the amount of antibody present.

After the substrate/solution has been added to the well containing the antigen-antibody complex, the enzyme attached to the secondary antibody will cause a colour change. The intensity of the colour is proportional to the intensity of the colour, therefore you can quantify the amount of antibody present by the intensity of the colour.