Antibodies

Question 1

What are antibodies?

Answer 1

Antibodies are proteins with specific binding sites synthesised by B-cells.

Question 2

How many binding sites do antibodies have?

Answer 2

2 identical binding sites. The antibody binding sites are complementary to a specific antigen.

Question 3

What are antibodies made up of?

Draw the structure of an antibody.

Answer 3

• Made up of 4 polypeptide chains.
• The chains of one pair are long and that is the heavy chains.
• The chains on the other pair are shorter and are known as light chains.
• Each antibody will have an antigen-binding site and it forms an antigen-antibody complex.
• The binding site of each antibody is different therefore it is the variable region.
• Each binding site has a sequence of amino acid that forms a specific 3d structure that allows the binding to occur.
• The rest of the antibody is the constant region, this binds to receptors on cells e.g. B-cells.

Question 4

Do antibodies destroy antigens?

Answer 4

Antibodies do not destroy antigens directly but prepare the antigen for destruction.
Different antibodies lead to destruction in different ways.

Question 5

How do antibodies help the destruction of bacterial cells?

Answer 5

• They stick the bacterial cells together, the clumps of bacterial cells would make it easier for phagocytes to locate them as they are less spread around the body.
• They then serve as markers that stimulate phagocytes to engulf the bacterial cells.

Question 6

How do monoclonal antibodies help to treat cancer?

Answer 6

As antibodies are very specific, monoclonal antibodies can be used to target one specific substance or cell.
Direct monoclonal antibody therapy can help to treat cancer by:
- MA is produced specifically to antigens of the cancer cells.
- Those antibodies are given to patients which allows the receptors to bind with the cancer cells.
- They attach to the surface of their cancer cells and block the chemical signals that stimulate uncontrollable growth.

Question 7

Give an example of MA that treats cancer and explain why is it better than other types of cancer treatments?

Answer 7

Example- Herceptin - MA used to treat breast cancer. The advantage of direct MA therapy is that antibodies are not toxic and highly specific, they lead to fewer side effects than other treatments.

Question 8

What is indirect MA therapy?

Answer 8

It involves attaching themselves to a radioactive or cytotoxic drug (a drug that kills cells) to the MA when the antibody binds to the cancer cell, it kills them.

Question 9

How are MA used in medical diagnosis?

Answer 9

Used for diagnosis of influenza, hepatitis, and chlamydia.
Men with prostate cancer often produce prostate specific antigen (PSA) which leads to a high level of it in the blood. By using MA, it can measure the amount in the blood and give an early warning.

Question 10

How does MA work in pregnancy tests?

Answer 10

• The placenta produces a hormone called hCG and it’s found in the mother’s urine. MA that is present on the test strip is linked to coloured particles. If hCG is present, they bind to these antibodies. The hCG-antibody-colour complex moves along the strip until it’s trapped by another type of antibody creating a coloured line.

Question 11

What are the ethical issues of using MA?

Answer 11

• Production of MA involves the use of mice.
• There have been deaths associated with the treatments.
• Risk of volunteers been harmed during the drug testing phase.