Definitions (Communicable disease, disease prevention and the immune system) 2 : Biodiversity, Evolution & Disease: Biology OCR A Level

Phagocytes

Specialised white blood cells that engulf and destroy pathogens. There are two types: neutrophils and macrophages.

Phagocytosis

The process by which phagocytes engulf and destroy pathogens.

Phagolysosome

A vesicle within a phagocyte formed by the fusion of a phagosome and lysosome.

Phagosome

The vacuole inside a phagocyte in which a foreign particle is engulfed.

Plasma cells

B lymphocytes that produce antibodies specific to a particular antigen.

Potato blight

A disease caused by the fungi-like protoctist Phytophthora infestans whose hyphae penetrate host cells, causing the collapse and decay of the leaves, fruit and tubers. Also known as tomato blight or late blight.

Primary immune response

The response of the immune system to a pathogen when it is first encountered. A small number of antibodies are produced slowly.

Protoctista

A group of eukaryotic, single-celled microorganisms that may cause disease. They digest cells and use the cell contents to reproduce.

Ring rot

A bacterial disease in tomatoes, potatoes and aubergines that results in damage to the leaves, fruit and tubers. It is caused by the Clavibacter michiganensis bacterium.

Ringworm

A fungal disease that affects mammals, causing grey-white, circular, crusty lesions on the skin.

A fungal disease that affects mammals, causing grey-white, circular, crusty lesions on the skin.

The response of the immune system to a pathogen when it is encountered for a second (third, fourth…etc.) time. Immunological memory gives a rapid production of a large number of antibodies.

Synthetic biology

The design and construction of new biological entities, as well as the reconstruction of pre-existing natural biological systems.

T helper cells

T lymphocytes with CD4 receptors on the cell surface membrane. These bind to antigens on antigen-presenting cells and secrete interleukins.

T killer cells

T lymphocytes that produce perforin, destroying pathogens with a specific antigen.

T lymphocytes

Lymphocytes that mature in the thymus gland. There are four main types: T helper cells, T killer cells, T memory cells and T regulatory cells.

T memory cells

T lymphocytes that provide immunological memory.

Tobacco mosaic virus (TMV)

A virus that infects many species of plants, in particular tobacco plants. It damages the leaves, flowers and fruit, and stunts plant growth.

T regulator cells

T lymphocytes that regulate the immune response by suppressing other T cells and maintaining tolerance to self-antigens.

Tuberculosis (TB)

A bacterial disease, caused by Mycobacterium tuberculosis and M. bovis, that damages lung tissue and weakens the immune system.

Vaccination

The deliberate exposure of an individual to antigens from a pathogen to provide artificial active immunity.

Vector

A living or non-living agent that transmits a pathogen between organisms.

Viruses

Non-living infectious agents that invade host cells and take over cell metabolism, replicating within them.