IB Biology SHL C3.2 - Defence Against Disease

Pathogen

a bacterium, virus, or other microorganism that can cause disease.

Immune System

A system (including the thymus and bone marrow and lymphoid tissues) that protects the body from foreign substances and pathogenic organisms by producing the immune response

Skin

cutaneous membrane

Mucous membrane

an epithelial tissue that secretes mucus and that lines many body cavities and tubular organs including the gut and respiratory passages.

Lysozyme

an enzyme found in saliva and sweat and tears that destroys the cell walls of certain bacteria

Clotting factors

proteins in the plasma that serve to activate various parts of the blood clotting process by being transformed from inactive to active forms. Also known as coagulation factors.

Prothrombin

a protein present in blood plasma that is converted into active thrombin during coagulation.

Thrombin

an enzyme in blood plasma that causes the clotting of blood by converting fibrinogen to fibrin.

Fibrinogin

precursor for fibrin involved in blood clotting

Fibrin

an insoluble protein formed from fibrinogen during the clotting of blood. It forms a fibrous mesh that impedes the flow of blood.

Innate immune system

a collection of nonspecific barriers and cellular responses that serve as an inborn first and second line of defense against pathogens

Adaptive immune system

Respond to specific antigens; Responds by remembering signature molecules, called antigens, from pathogens to which the body has previously been exposed

Phagocyte

A white blood cell that destroys pathogens by engulfing them and breaking them down

Antigen

A protein that, when introduced in the blood, triggers the production of an antibody

Antibody

An antigen-binding immunoglobulin, produced by B cells, that functions as the effector in an immune response.

Lysosome

cell organelle filled with enzymes needed to break down certain materials in the cell

Phagosome

Intracellular vesicle containing material taken up by phagocytosis.

Lymphocytes

The two types of white blood cells that are part of the body's immune system: B lymphocytes form in the bone marrow and release antibodies that fight bacterial infections; T lymphocytes form in the thymus and other lymphatic tissue and attack cancer cells, viruses, and foreign substances.

T4 helper lymphocytes

white blood cells that are destroyed by HIV

B lymphocytes

form in the bone marrow and release antibodies that fight bacterial infections

Glycoproteins

Membrane carbohydrates that are covalently bonded to proteins.

MHC protein

Proteins on the surface of cells that identifies that cell as it's own and that it is not foreign.

Plasma cells

Cells that develop from B cells and produce antibodies.

Memory cells

General term for lymphocytes that are responsible for immunological memory and protective immunity.

Clonal selection

A fundamental mechanism in the development of immunity; antigenic molecules select or bind to specific B or T lymphocytes, activating them; the B cells then differentiate into plasma cells and memory cells

Immunity

the ability of an organism to resist a particular infection or toxin by the action of specific antibodies or sensitized white blood cells.

HIV

human immunodeficiency virus

AIDS

A serious (often fatal) disease of the immune system transmitted through blood products especially by sexual contact or contaminated needles.

Antibiotics

compounds that block the growth and reproduction of bacteria

Natural selection

A natural process resulting in the evolution of organisms best adapted to the environment.

Zoonoses

diseases that are naturally spread from their usual animal host to humans

Vaccines

dose of a disabled or destroyed pathogen used to stimulate a long-term immune defense against the pathogen. A weakened form of the virus is given to the person so their immune system can build up immunity to the virus.

Immunization

The deliberate exposure of a pathogen to produce memory cells.

Herd immunity

the resistance to the spread of a contagious disease within a population that results if a sufficiently high proportion of individuals are immune to the disease, especially through vaccination.

Pandemic

Disease that occurs over a wide geographic area and affects a very high proportion of the population.

Epidemic

a widespread occurrence of an infectious disease in a community at a particular time.

Percentage difference

The difference between two values divided by the average and shown as a percentage.

Percentage change

change/original x 100