Disease OCR A level Biology

active immunity

Resistance in an organism that has developed through the production of specific antibodies in response to a pathogen. (It provides long-lasting immunity as memory cells are produced)

Agglutin

Chemicals that cause pathogens to aggregate together, aiding phagocytosis. (Antibodies can act as agglutinins)

antibiotic

A chemical or compound produced by a living organism that kills or prevents the growth of bacteria

antibiotic resistant bacteria

Bacteria that mutate to become resistant to an antibiotic, survive and reproduce very rapidly, passing on their antibiotic resistance

Antibodies

Immunoglobulins produced by B-lymphocytes in response to a specific antigen, triggering an immune response

Antigen

A chemical present on the surface of a cell that induces an immune response

antigen presenting cells

A macrophage that displays foreign antigens

anti-toxins

Chemicals produced by white blood cells that neutralise toxins released by pathogens

artificial active immunity

The production of antibodies by the immune system following the exposure to a weakened, attenuated or dead pathogen. (e.g.: by vaccination)

artificial passive immunity

The immunity acquired from the administration of specific antibodies from another organism. (e.g.: by vaccination)

atheletes foot

A form of ringworm in humans that affects the feet, resulting in cracking and scaling of the skin

autoimmune disease

A condition in which the immune system attacks and destroys healthy body tissue. (e.g.: arthritis, lupus)

Bacteria

Prokaryotic cells that have cell walls but lack organelles. (Some bacteria are pathogenic, producing toxins that damage host cells)

bacterial menigitis

A severe form of meningitis caused by bacterial infection of the meninges. (Complications of bacterial meningitis include septicaemia; a symptom of this is a rash of purple discolouration that does not fade when a glass is pressed against it)

B effector cells

A type of B lymphocyte that divides to form plasma cells

Black Sigatoka

A fungal disease in tomatoes caused by Mycosphaerella fijiensis, the hyphae of which penetrate and digest host leaf cells, turning them black

B lymphocytes

Lymphocytes that mature in the bone marrow.(There are three main types; plasma cells, B effector cells and B memory cells)

B memory cells

B lymphocytes that provide immunological memory

Callose

A plant polysaccharide that contains β-1,3 and β-1,6 linkages between glucose molecules. (It is deposited between the cell walls and cell membrane in cells adjacent to infected cells, serving as a defence against pathogens. It is also found in the cell walls of infected cells and the plasmodesmata between infected cells)

chitinase

Enzymes that degrade chitin in fungal cell walls.

clonal expansion

The mass proliferation of specific antibody-producing cells.

clonal selection

The identification of an antibody-producing cell with complementary receptors to the shape of a specific antigen

Clostridum difficile

A type of bacteria found in the gut of some individuals which is resistant to most antibiotics

communicable disease

A disease that is caused by a pathogen and transmitted directly between organisms

Cytokines

Cell-signalling molecules produced by mast cells in damaged tissue. (They attract white blood cells to the site of damage)

Direct transmission

The transfer of a pathogen directly from one organism to another. (This can occur via direct contact, ingestion or the sharing of contaminated needles.)

Epidemic

A rapid rise in the incidence of a communicable disease at a local or national level.

Expulsive reflexes

Coughs or sneezes initiated upon irritation of the respiratory tract. (They remove microorganisms-containing mucus from the gaseous exchange system)

Fungi

Eukaryotic, often multicellular organisms that may cause disease. (They digest and destroy cells, and produce spores that can spread rapidly between organisms)

Glucanase

Enzymes produced by plants that decompose glucans, polysaccharides found in oomycete cell walls.

Histamine

A chemical produced by mast cells in damaged tissue. It makes blood vessels dilate and causes their walls to become leakier

Human immunodeficiency virus (HIV)

An infectious virus that destroys T helper cells, weakening the immune system of the body. (HIV makes an individual more susceptible to opportunistic infections and can lead to AIDS Acquired Immunodeficiency Syndrome)

indirect transmission

The transfer of a pathogen indirectly between organisms via fomites, vectors, droplet infection or soil contamination

inflammation

A localised response of vascular tissue to pathogens, damage or irritants. (It is characterised by pain, redness, heat and swelling)

Influenza virus

A common viral infection caused by the family of viruses, Orthomyxoviridae, that destroys ciliated epithelial cells in the gaseous exchange system, exposing the airways to secondary infection

Interleukins

Cytokines produced by T helper cells that stimulate B cells

Lymphocytes

White blood cells that contribute to the specific immune response

Lysosomes

A membrane-bound organelle that contains hydrolytic enzymes

Malaria

A disease caused by the protoctista Plasmodium that lives within two hosts, mosquitoes and humans. (It causes recurrent episodes of fever and can be fatal)

Mast cells

Specialised cells in connective tissue that are important in the inflammatory response, releasing histamines and cytokines

MRSA

A type of bacteria that is resistant to the antibiotic methicillin.

mucous membrane

The membranes lining body cavities that secrete a sticky mucus.

natural active immunity

The production of antibodies by the immune system following infection

natural passive immunity

The immunity acquired by an infant mammal when antibodies are transferred through the placenta and the colostrum from the mother

Non-specefic defenses

Defences that are always present and are the same for all organisms. (e.g. skin, blood clotting, inflammation, mucous membranes and expulsive reflexes)

Opsonins

Chemicals that bind to and tag foreign cells, making them easily recognisable to phagocytes

passive immunity

Resistance in an organism acquired via the transfer of antibodies. (It provides short-term immunity as no memory cells are produced)

Pathogen

A disease-causing microorganism. (Includes bacteria, viruses, fungi and protoctista)

Penicillin

The first conventional, effective and safe antibiotic derived from the mould Penicillium chrysogenum. (It was first discovered by Alexander Fleming

Personalised medicine

A form of medical care that enables doctors to provide healthcare that is customised to an individual's genotype

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 protists 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)

Protocista

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

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

secondary immune response

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

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