OCR AS Biology- The Immune System

Complete set of revision notes on the immune system for OCR Biology, AS level.

Contains: Key Definitions, Diagrams and Explanations

Topics: Antibodies, Antigens, Disease, Primary and Secondary Response, Lymphocytes, Phagocytes, Macrophages and Pathogens.

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  • Created by: Abbie_Mac
  • Created on: 14-03-13 14:22
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Basic Immunity
Parasite ­ organisms that live in or on another living thing, harming their host,
usually by taking their nutrients. External parasites live on the host, e.g. head lice,
and internal parasites live inside the host, e.g. tapeworm.

Pathogens ­ pathogens are organisms that cause disease, taking nutrients from…

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Antigen ­ molecules which stimulate an immune response. A foreign antigen will
be detected by the immune system and will stimulate the production of antibodies.
These antibodies will be specific to the antigen. As the antigen is specific to the
organism, the antibody is specific to the pathogen. Antigens are…

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Mode of action of antibodies:

-The variable region of the antibody binds to a pathogen's antigens, which
lay on the cell membrane. This is known as neutralisation. This antigen
may be used as a binding site, so when the antibody binds to that antigen
the pathogen will be unable to…

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Macrophages:

Macrophages partially break down pathogens, separating the antigens
from the rest of the microorganism. It then displays this antigen on its cell
membrane, becoming an antigen-presenting cell. It then travels round the body
to help with clonal selection, finding the correct T lymphocyte. They also release
monokines that attract…

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