C3.2 Defence Against Disease

Pathogen

A microorganism that can cause disease, typically viruses, bacteria, fungi, and protists.

Immune System

A complex network of cells, tissues, and organs that work together to defend the body against pathogens.

Skin

A primary physical barrier that prevents pathogens from entering the body.

Mucous Membrane

Soft areas of skin that trap pathogens using mucus and produce enzymes like lysozyme.

Lysozyme

An enzyme that breaks down the cell walls of bacteria, found in bodily secretions.

Clotting Factors

Proteins that help in the blood coagulation process to prevent blood loss and pathogen entry.

Prothrombin

An inactive protein that is converted into thrombin during the blood clotting process.

Thrombin

An enzyme that converts fibrinogen into fibrin in the blood coagulation cascade.

Fibrinogen

A soluble plasma protein that is converted to fibrin during blood clotting.

Fibrin

An insoluble protein that forms a mesh to stabilize a blood clot.

Innate Immune System

The non-specific first line of defense against pathogens, responding to broad categories.

Adaptive Immune System

A specific immune response that adapts over time to recognize and remember pathogens.

Phagocyte

A type of white blood cell that engulfs and digests pathogens.

Antigen

A recognition molecule that can trigger an immune response and antibody production.

Antibody

A protein produced by B-lymphocytes that specifically binds to antigens.

Lysosome

An organelle that contains enzymes to digest engulfed particles within phagocytes.

Memory Cells

Long-lived cells that remember a specific pathogen and produce a faster immune response upon re-exposure.

Clonal Selection

The process by which specific B-cells are activated and proliferate into plasma cells that produce antibodies.

Herd Immunity

Resistance to the spread of an infectious disease within a population due to a significant proportion being immune.

Vaccines

Biological preparations that stimulate an immune response to confer immunity without causing the disease.

Zoonoses

Diseases that are transmitted from animals to humans.

AIDS

Acquired Immunodeficiency Syndrome, a disease caused by HIV leading to immune system failure.

Antibiotics

Chemicals that inhibit the growth of, or kill, bacteria, but have no effect on viruses.

Natural Selection

The process through which species evolve, where traits that enhance survival become more common in a population.