AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
The antibodies are specific to one binding site on one protein antigen and…
Full specification wording
Producing monoclonal antibodies: The antibodies are specific to one binding site on one protein antigen and so are able to target a specific chemical or specific cells in the body.
An antibody is a protein with a binding site shaped to fit a particular antigen.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 3 of 8
- 2 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
An antibody is a protein with a binding site shaped to fit a particular antigen. A monoclonal antibody has one type of binding site, so it binds only to one specific binding site on one protein antigen. This is like a lock and key: the antibody's binding site is complementary to the antigen's shape. Because binding is so specific, the antibody can target a particular chemical, such as a hormone, or a particular cell type, such as a cancer cell, without affecting other molecules or cells. For example, a monoclonal antibody can be designed to bind to a protein on the surface of a cancer cell, carrying a drug directly to that cell. Note that this entire topic is assessed at Higher Tier only.
What earns the marks
- An antibody has a binding site with a shape complementary to a specific antigen.
- A monoclonal antibody is specific to one binding site on one protein antigen.
- Specific binding allows the antibody to target a particular chemical in the body.
- Specific binding also allows the antibody to target particular cells, such as cancer cells.
- The lock-and-key or complementary-shape model explains why only one antigen fits the antibody.
- Targeting is possible because the antibody binds only where the complementary antigen is present.
Common mistakes and how to put them right
Saying an antibody binds to any antigen.
Put it right: It binds only to the antigen with a complementary shape.
Confusing antigen with antibody.
Put it right: The antigen is the target molecule, while the antibody is the protein that binds it.
Thinking specificity means the antibody is strong.
Put it right: Specificity means it binds only to one particular antigen binding site.
Exam tips
- Use the phrase complementary shape when explaining specificity.
- Give one named example of targeting, such as a cancer cell or a hormone, to show understanding.
- Remember that the production and application of monoclonal antibodies is a Higher Tier only topic.
Try the lesson
The start of the Producing monoclonal antibodies: The antibodies are specific to one binding site on one protein antigen and so are able to target a specific chemical or specific cells in the body. lesson, made from checked teaching notes for this specification point.
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A monoclonal antibody is specific to one binding site on one protein antigen. What does this allow the antibody to do?
Listen
An antibody is a protein with a binding site shaped to fit a particular antigen. A monoclonal antibody has one type of binding site, so it binds only to one specific binding site on one protein antigen. This is like a lock and key: the antibody's binding site is complementary to the antigen's shape. Because binding is so specific, the antibody can target a particular chemical, such as a hormone, or a particular cell type, such as a cancer cell, without affecting other molecules or cells. For example, a monoclonal antibody can be designed to bind to a protein on the surface of a cancer cell, carrying a drug directly to that cell. Note that this entire topic is assessed at Higher Tier only. A strong answer earns marks for these points. An antibody has a binding site with a shape complementary to a specific antigen. A monoclonal antibody is specific to one binding site on one protein antigen. Specific binding allows the antibody to target a particular chemical in the body. Specific binding also allows the antibody to target particular cells, such as cancer cells. Exam tip: Use the phrase complementary shape when explaining specificity.
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Key words
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Antigen-antibody specificity
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Complementary shapes and molecular recognition
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See every definition
- Antigen-antibody specificity
- An antibody is specific to one binding site on one protein antigen, so it binds only where the complementary antigen is present.
- Complementary shapes and molecular recognition
- The antibody's binding site has a shape complementary to the antigen, like a lock and key, so only one antigen fits.
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