3.14 Uses of monoclonal antibodies
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Give three uses of monoclonal antibodies.
Mark scheme
Any three from:
- pregnancy tests (1)
- diagnosis / measuring hormones or chemicals in blood / detecting pathogens (1)
- research / locating molecules in cells using fluorescent dye (1)
- treating cancer / delivering drugs to cancer cells (1)
Model answer
Pregnancy tests, finding the levels of hormones in the blood for diagnosis, and treating cancer.
Explain how a pregnancy test stick shows that a woman is pregnant.
Mark scheme
- hCG (in urine) binds to (mobile) antibodies (attached to blue beads) (1)
- (moves along to the) test line where fixed antibodies bind to hCG (1)
- blue beads collect so a blue line appears at the test line (1)
- control line also turns blue to show the test has worked (1)
Model answer
If the woman is pregnant, hCG in her urine binds to mobile antibodies attached to blue beads. When it reaches the test line, antibodies fixed to the stick trap the hCG, so the blue beads build up and a blue line appears. The control line also turns blue to show the test has worked.
A pregnancy test shows a blue line at the control line only.
What does this result show?
Mark scheme
- the woman is not pregnant / no hCG (1)
- the test has worked (1)
Model answer
The woman is not pregnant, because there is no line at the test line, and the test has worked, because the control line is blue.
Explain how monoclonal antibodies can be used to treat cancer with fewer side effects than ordinary chemotherapy.
Mark scheme
- antibodies made that bind to antigens (only) on cancer cells (1)
- drug / toxin / radioactive substance attached to the antibody (1)
- delivered to cancer cells only, so normal cells not harmed (1)
Model answer
Antibodies are made that bind only to antigens on the cancer cells. A drug or radioactive substance is attached to them, so it is carried straight to the cancer cells and normal body cells are not harmed.
Give one reason why monoclonal antibodies are not as widely used as scientists first hoped.
Mark scheme
more side effects than expected / expensive
Model answer
They have caused more side effects than expected.
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