Monoclonal antibodies – GCSE Biology exam questions with mark scheme

1Grade 8–9HigherTriple only6 marks

Monoclonal antibodies have many uses in medicine and research.

(a) Describe how monoclonal antibodies are produced. [4]

(b) Give one use of monoclonal antibodies other than treating disease. [1]

(a) a mouse is injected with an antigen to stimulate its lymphocytes (to make a specific antibody); allow B cells for lymphocytes(1)
(a) the lymphocytes which make the required antibody are collected / removed(1)
(a) lymphocytes are combined / fused with a tumour cell to make a hybridoma (cell); allow cancer / myeloma cell for tumour cell(1)
(a) a single hybridoma cell divides / is cloned (to make many identical cells) or the antibody (made by the hybridoma cells) is collected and purified; either idea scores(1)
(b) any one from: pregnancy tests; measuring levels of hormones / chemicals in blood; detecting pathogens; locating / identifying specific molecules in cells or tissues (by binding fluorescent dye); allow diagnosing (a named) disease(1)
(c) they cause more side effects than expected (allow they cause side effects)(1)
Answer: (a) mouse lymphocytes + tumour cell → hybridoma → cloned → antibody collected (b) e.g. pregnancy tests (c) more side effects than expected
Examiner tip: Name both cell types fused (lymphocyte AND tumour cell) and the product (hybridoma) — vague 'cells are joined' is not credited.

2Grade 4–5HigherTriple only3 marks

Monoclonal antibodies are made in laboratories.

(a) What are monoclonal antibodies? [2]

(b) To make monoclonal antibodies, a mouse is first injected with an antigen.

Which type of cell is then taken from this mouse?

Tick (✓) one box.

☐ Lymphocyte ☐ Phagocyte ☐ Red blood cell ☐ Tumour cell [1]

(a) (antibodies that are) identical copies / all the same; allow produced from a single clone of cells; ignore 'made in a lab'(1)
(a) specific to / bind to only one binding site / antigen / protein; allow target only one type of molecule(1)
(b) Lymphocyte (only) ticked; if more than one box ticked, no mark(1)
Answer: (a) identical antibodies from a single clone of cells, each specific to one binding site (b) lymphocyte
Examiner tip: 'Antibodies made in a lab' scores nothing — you need BOTH ideas: identical copies (one clone) AND specific to one binding site.

3Grade 6–7HigherTriple only5 marks

The diagram shows a pregnancy test stick.

A pregnant woman has the hormone hCG in her urine.

Zone A contains antibodies attached to blue beads. They bind to hCG. These antibodies can move along the strip.
Zone B contains antibodies that are fixed to the strip. They bind to hCG.
Zone C contains antibodies that are fixed to the strip. They bind to the antibodies from zone A.

(a) Explain why a blue line appears in zone B only if the woman is pregnant. [3]

(b) A blue line appears in zone C whether or not the woman is pregnant.

Explain why zone C is needed on the test stick. [2]

(a) hCG (in urine) binds to the (monoclonal) antibodies (attached to blue beads) in zone A(1)
(a) hCG–antibody–bead (complex) moves along (the strip) to zone B(1)
(a) (fixed) antibodies in zone B bind to the hCG, so the blue beads are held / collect there (giving a blue line); allow if no hCG, blue beads are not held at B (so no line)(1)
(b) any antibodies (with beads) from zone A that reach zone C bind there / are held there, so a line shows(1)
(b) (shows that) the test is working / urine has moved along the strip; allow so a negative result can be trusted; ignore 'to check the result' unqualified(1)
Answer: (a) hCG binds to bead-linked antibodies at A, travels to B, fixed antibodies at B bind hCG so beads collect — blue line. (b) Control: beads bind at C to show the test has worked.
Examiner tip: Students lose the zone B mark by saying the beads 'react' — say the fixed antibodies BIND to the hCG that is already attached to the bead antibodies.

4Grade 6–7HigherTriple only4 marks

The diagram shows the stages in making a monoclonal antibody.

(a) Name cell X. [1]

(b) Explain why cell X is fused with cell Y. [2]

(a) lymphocyte; allow B cell / white blood cell that makes antibodies; do not accept phagocyte(1)
(b) cell X / lymphocyte makes the (specific) antibody but does not divide (in culture / outside the body)(1)
(b) cell Y / tumour cell divides rapidly / many times; so the hybridoma (cell Z) makes the antibody and divides; allow cell Z named as hybridoma for this idea(1)
(c) so all the cells / clones are identical so all antibodies made are identical / bind to the same (one) binding site / antigen(1)
Answer: (a) lymphocyte (b) lymphocyte makes antibody but doesn't divide; tumour cell divides rapidly — hybridoma does both (c) so all antibodies are identical / same binding site
Examiner tip: In (b) give BOTH halves — what the lymphocyte brings (makes the antibody) and what the tumour cell brings (divides rapidly).

5Grade 6–7HigherTriple only4 marks

Breast cancer cells have a protein on their cell membrane that is not found on healthy cells.

Scientists made a monoclonal antibody that binds to this protein. They attached a toxic drug to the antibody.

(a) Explain how this treatment kills cancer cells but does not harm most healthy cells. [3]

(b) Monoclonal antibodies can treat cancer in other ways.

Give one other way. [1]

(a) the antibody is specific to / complementary to / binds only to the protein (antigen) on the cancer cells(1)
(a) so the toxic drug is carried / delivered (only) to the cancer cells(1)
(a) (the drug kills the cancer cell but) the antibody does not bind to healthy cells (as they do not have the protein), so healthy cells are not exposed to the drug; ignore 'targets cancer cells' alone(1)
(b) any one from: carrying a radioactive substance (to the cancer cells); carrying a chemical that stops cells growing / dividing; marking / flagging the cancer cells so the immune system attacks / destroys them; allow stimulating the immune system (to attack cancer cells); do not accept a toxic drug (given in stem)(1)
Answer: (a) antibody binds only to the protein on cancer cells, carrying the drug to them; healthy cells lack the protein so are not affected (b) e.g. carry a radioactive substance / stimulate the immune system
Examiner tip: 'It targets cancer cells' is too vague — say the antibody BINDS to the specific protein/antigen, so the drug is delivered only there.

6Grade 6–7HigherTriple only4 marks

Hybridoma cells are grown in a culture to make a monoclonal antibody.

(a) A single hybridoma cell divides once every 16 hours. Every new cell also divides every 16 hours.

Calculate the number of cells after 4 days. [2]

(b) A large culture makes 0.35 g of antibody in each dm³.

20% of the antibody is lost when the antibody is purified.

One patient needs 4.2 g of purified antibody for a course of treatment.

Calculate the volume of culture needed for one patient. [2]

(a) number of divisions = (4 × 24) ÷ 16 = 6(1)
(a) 2⁶ = 64 (cells); 64 with no working scores 2; if the number of divisions is wrong, allow 1 mark for 2ⁿ correctly worked out for their n (e.g. 2⁴ = 16); 2 × 6 = 12 scores the first mark only(1)
(b) purified antibody per dm³ = 0.35 × 0.8 = 0.28 (g); allow 0.35 − 0.07; or mass of antibody needed before purification = 4.2 ÷ 0.8 = 5.25 (g)(1)
(b) 4.2 ÷ 0.28 (or 5.25 ÷ 0.35) = 15 (dm³); 15 with no working scores 2; allow 1 mark for 4.2 ÷ 0.35 = 12 (dm³)(1)
Answer: (a) 64 cells (b) 15 dm³
Examiner tip: Convert days to hours FIRST (4 days = 96 h), and remember cells double each division — it is 2⁶, not 2 × 6.

7Grade 4–5HigherTriple only4 marks

A scientist wants to find out where a particular protein is found in a thin slice of brain tissue.

(a) Explain how the scientist could use monoclonal antibodies to find where the protein is. [3]

(b) A student says the antibodies will also stick to other proteins in the brain tissue.

Explain why the student is wrong. [1]

(a) make / use monoclonal antibodies that are specific to / bind to the protein; allow antibodies complementary to the protein(1)
(a) attach a fluorescent dye (to the antibodies); allow a (coloured) marker / label(1)
(a) (add to the tissue and) the antibodies bind to the protein so the dye glows / shows up (under a microscope / UV light) where the protein is(1)
(b) the antibodies (are monoclonal so) are all identical and bind to only one binding site / (shape of) antigen / protein; allow the antibody shape only fits / is complementary to that protein(1)
Answer: (a) antibodies specific to the protein, labelled with fluorescent dye, bind to it so it glows where the protein is (b) each antibody binds to one specific binding site only
Examiner tip: Don't forget to say the dye is ATTACHED to the antibody — otherwise there is no way to see where it has bound.

8Grade 4–5HigherTriple only4 marks

A grower sees pale patches on the leaves of some tomato plants.

She uses a testing kit containing monoclonal antibodies to find out if three plants are infected with tobacco mosaic virus (TMV).

A coloured line appears at T if TMV is present. A coloured line should always appear at C.

The diagram shows her results.

(a) Which plant is infected with TMV? [1]

(b) Explain why the result for plant 3 cannot be used. [1]

Explain why. [1]

(d) Give one other way the grower could identify the disease. [1]

(a) plant 2(1)
(b) no line at C, so the test has not worked / is not valid; allow the sample did not move along the strip(1)
(c) the antibodies are specific to (an antigen / protein on) TMV so will not bind to (antigens on) the fungus / black spot(1)
(d) any one from: use a gardening manual / website; send a sample for laboratory testing; allow compare with photographs of diseased plants; ignore 'look at the leaves' unqualified(1)
Answer: (a) plant 2 (b) control line missing — test failed (c) antibodies only bind to TMV antigens (d) gardening manual/website or lab testing
Examiner tip: No control line means the test failed — it does NOT mean the plant is healthy.

9Grade 8–9HigherTriple only6 marks

Monoclonal antibodies are used to diagnose and to treat diseases.

Evaluate the use of monoclonal antibodies in medicine. [6]

specific to one binding site / antigen so bind only to the target molecule or cell(1)
diagnosis: pregnancy tests, detecting pathogens, measuring hormone levels — quick / accurate / can be done at home(1)
locating molecules (e.g. blood clots, cancer cells) by attaching fluorescent dye(1)
cancer treatment: carry radioactive substance / toxic drug / chemical that stops cell division directly to cancer cells(1)
so fewer healthy cells damaged than with chemotherapy / radiotherapy (fewer side effects such as hair loss)(1)
can stimulate the immune system to attack cancer cells(1)
once a hybridoma is cloned, large amounts of identical antibody can be made(1)
disadvantage: cause more side effects than expected (e.g. fever, vomiting, allergic reaction, low blood pressure)(1)
disadvantage: so not yet as widely used as hoped(1)
disadvantage: expensive / time-consuming to develop and test(1)
disadvantage: mice are used — ethical objections; mouse antibodies may trigger an immune response in humans(1)
conclusion: e.g. benefits of targeted treatment and accurate diagnosis outweigh risks, but each use must be tested in trials / side effects monitored(1)

Level	Marks	What it looks like
Level 3	5–6	Clear, detailed evaluation linking specificity to at least one diagnostic and one treatment use, with at least one disadvantage explained, ending in a conclusion that is justified by the points made.
Level 2	3–4	Some advantages and at least one disadvantage given with some explanation; any conclusion is not fully supported or the answer is one-sided in detail.
Level 1	1–2	Simple statements of uses or of an advantage or disadvantage, with little or no explanation or comparison.
No relevant content	0	Nothing worthy of credit.

Answer: Balanced answer: specificity gives accurate diagnosis (pregnancy tests, pathogens, hormones) and targeted cancer treatment harming fewer healthy cells; but more side effects than expected, expensive, use of mice; justified conclusion.
Examiner tip: Most answers stay in Level 2 because they list uses — to reach Level 3 you must weigh advantages AGAINST disadvantages and finish with a justified conclusion.

10Grade 8–9HigherTriple only6 marks

Doctors compared two treatments for one type of cancer.

	Group A: monoclonal antibody	Group B: chemotherapy
Number of patients	250	320
Number alive after 3 years	185	208
Number with fever and chills	95	22
Number with hair loss	6	230
Number with a serious allergic reaction	14	3

(a) Calculate the percentage of patients in group A who were alive after 3 years. [2]

(b) 65% of patients in group B were alive after 3 years.

Evaluate the use of the monoclonal antibody instead of chemotherapy to treat this type of cancer.

Use information from the table. [4]

(a) 185 ÷ 250 (× 100)(1)
(a) = 74 (%); 74 with no working scores 2(1)
(b) one comparison from the list, supported by data from the table:
• (for) higher percentage alive after 3 years with the antibody: 74% vs 65% (allow ecf from (a)); do not accept 'more patients survived with chemotherapy' from 208 vs 185 (groups are different sizes)
• (for) far fewer had hair loss: 2.4% vs about 72% (allow 6 vs 230 patients)
• (against) a higher percentage had fever and chills: 38% vs about 7%
• (against) a higher percentage had a serious allergic reaction: 5.6% vs about 0.9%
ignore 'more side effects' unless supported by data from the table(1)
(b) a second, different comparison from the list(1)
(b) a third, different comparison from the list
for this third mark, at least one 'for' and at least one 'against' comparison must be given(1)
(b) conclusion with justification, e.g. use the antibody because survival is higher and fever / allergy can usually be treated, or doctors should weigh the risk of a serious allergic reaction for each patient; max 3 if no conclusion(1)
Answer: (a) 74% (b) for: survival 74% vs 65%, much less hair loss (2.4% vs 72%); against: more fever/chills (38% vs 6.9%) and serious allergic reactions (5.6% vs 0.94%); justified conclusion
Examiner tip: The groups are different sizes, so compare PERCENTAGES not raw numbers — and 'evaluate' needs a conclusion or you cap at 3.

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