Edexcel GCSE Biology (1BI0) — Health, Disease and Medicines
If you want to hit a bullseye, you need a precise arrow. In medicine, monoclonal antibodies act as biological arrows, designed to seek out and bind to one specific target in the body.
Cancer cells are masters of disguise, often hiding from the body's natural defences. However, they possess unique proteins on their cell membranes called tumour markers, which are not found in significant amounts on normal healthy cells. Monoclonal antibodies are manufactured to have a shape that is completely complementary to these markers, allowing them to bind specifically to cancer cells.
They are used in targeted therapy to treat cancer through three main mechanisms:
Radioactive isotopes attached to monoclonal antibodies are not just for treatment; they are also used for diagnosis. For example, radioactively labelled antibodies can be injected into a patient and tracked using a PET scanner to locate the exact position of hidden tumours.
Traditional treatments like chemotherapy and radiotherapy are broad and non-specific, whereas monoclonal antibodies offer a highly targeted approach.
| Feature | Monoclonal Antibodies | Chemotherapy & Radiotherapy |
|---|---|---|
| Targeting | High specificity; binds only to the complementary tumour marker on cancer cells. | Non-specific; targets all rapidly dividing cells in the body. |
| Effect on Healthy Cells | Healthy cells are preserved and undamaged. | Destroys healthy, rapidly dividing cells (e.g., in hair follicles, bone marrow, and digestive lining). |
| Side Effects | Reduced systemic side effects, though can cause immune reactions (fever, rashes) due to mouse proteins. | Severe systemic side effects, including hair loss, extreme nausea, and lowered immunity. |
| Dosage Required | Lower total dose needed because the drug is concentrated directly at the tumour site. | Higher doses required as the treatment is distributed throughout the entire body. |
Despite their incredible precision, monoclonal antibodies are not perfect. Because they are originally produced using mouse lymphocytes, the human immune system can sometimes recognise the mouse-derived proteins as foreign invaders.
This recognition can trigger unwanted immune reactions in the patient. Consequently, they can cause unexpected side effects like fever, rashes, allergic reactions, and low blood pressure, which has limited their widespread use compared to early expectations.
Sometimes, new monoclonal antibody conjugates or antibiotics are tested on cell cultures in a petri dish. Scientists measure their effectiveness by calculating the area of the clear zone around the treatment disc, known as the zone of inhibition.
The area is calculated using the formula:
A paper disc soaked in a targeted toxic drug is placed on a cancer cell culture. After 48 hours, a clear circular zone of inhibition forms around the disc with a radius of 14 mm. Calculate the area of this zone. Give your answer to 3 significant figures.
Step 1: Identify the values.
Step 2: Substitute into the equation.
Step 3: Calculate.
Students often state that monoclonal antibodies "kill cancer cells directly". Remember that the antibodies themselves do not usually kill the cell; they either trigger the immune system to do it, block growth receptors, or deliver a toxic payload that does the killing.
In treatment-based explanation questions, you must use the exact term "tumour marker" to secure the first mark when describing what the antibody binds to.
If a 6-mark question asks you to "evaluate" the use of monoclonal antibodies, you must discuss both their advantages (like fewer side effects) AND their disadvantages (such as triggering an immune response because they contain mouse-derived proteins).
Do not confuse the terms 'fuse' and 'mix'. When describing the creation of a hybridoma in an exam, you must explicitly state that the lymphocyte and myeloma cells are fused together.
Monoclonal antibody
Identical copies of a specific type of antibody, produced from a single clone of hybridoma cells, designed to bind to one specific antigen.
Antigen
A protein on the surface of a cell that can trigger an immune response.
Tumour marker
A specific antigen found on the cell membrane of cancer cells, which acts as a target for monoclonal antibodies.
Lymphocyte
A type of white blood cell produced by the immune system that secretes antibodies.
B-lymphocyte
A specific type of lymphocyte that produces and secretes antibodies.
Myeloma
A type of cancerous white blood cell that can divide continuously and indefinitely.
Fused
The process of joining two different cells, such as a lymphocyte and a myeloma cell, to form a single hybrid cell.
Hybridoma
A cell formed by the fusion of an antibody-producing lymphocyte and a rapidly dividing myeloma cell.
Healthy cells
Normal body cells that do not possess the specific tumour markers targeted by a treatment, thus remaining largely undamaged during targeted therapy.
Targeted therapy
A type of medical treatment that uses substances like monoclonal antibodies to precisely identify and attack only diseased cells.
Toxic drugs
Potent chemicals or chemotherapy agents attached to monoclonal antibodies to be delivered directly to a target cell.
Radioactive isotopes
Unstable atoms that emit radiation; used with antibodies to kill cancer cells or for diagnostic imaging (e.g., PET scans).
Chemotherapy
A traditional cancer treatment that uses toxic drugs to kill all rapidly dividing cells in the body, which often causes collateral damage to healthy tissues.
Radiotherapy
A traditional cancer treatment that uses high doses of radiation to kill rapidly dividing cells.
Specificity
The property of an antibody that allows it to bind to only one particular, complementary shape of antigen.
Side effects
Unintended and usually unpleasant physical reactions to a treatment, such as nausea, hair loss, or immune responses.
Phagocytes
A type of white blood cell that identifies, engulfs, and destroys foreign substances or diseased cells.
Zone of inhibition
The clear area in a cell culture or agar plate where growth has been inhibited by a drug or toxic substance.
Put your knowledge into practice — try past paper questions for Biology
Monoclonal antibody
Identical copies of a specific type of antibody, produced from a single clone of hybridoma cells, designed to bind to one specific antigen.
Antigen
A protein on the surface of a cell that can trigger an immune response.
Tumour marker
A specific antigen found on the cell membrane of cancer cells, which acts as a target for monoclonal antibodies.
Lymphocyte
A type of white blood cell produced by the immune system that secretes antibodies.
B-lymphocyte
A specific type of lymphocyte that produces and secretes antibodies.
Myeloma
A type of cancerous white blood cell that can divide continuously and indefinitely.
Fused
The process of joining two different cells, such as a lymphocyte and a myeloma cell, to form a single hybrid cell.
Hybridoma
A cell formed by the fusion of an antibody-producing lymphocyte and a rapidly dividing myeloma cell.
Healthy cells
Normal body cells that do not possess the specific tumour markers targeted by a treatment, thus remaining largely undamaged during targeted therapy.
Targeted therapy
A type of medical treatment that uses substances like monoclonal antibodies to precisely identify and attack only diseased cells.
Toxic drugs
Potent chemicals or chemotherapy agents attached to monoclonal antibodies to be delivered directly to a target cell.
Radioactive isotopes
Unstable atoms that emit radiation; used with antibodies to kill cancer cells or for diagnostic imaging (e.g., PET scans).
Chemotherapy
A traditional cancer treatment that uses toxic drugs to kill all rapidly dividing cells in the body, which often causes collateral damage to healthy tissues.
Radiotherapy
A traditional cancer treatment that uses high doses of radiation to kill rapidly dividing cells.
Specificity
The property of an antibody that allows it to bind to only one particular, complementary shape of antigen.
Side effects
Unintended and usually unpleasant physical reactions to a treatment, such as nausea, hair loss, or immune responses.
Phagocytes
A type of white blood cell that identifies, engulfs, and destroys foreign substances or diseased cells.
Zone of inhibition
The clear area in a cell culture or agar plate where growth has been inhibited by a drug or toxic substance.
