Infection & ResponseDefinitions
Key Definitions
Part of Pathogens and Disease Transmission — GCSE Biology
This definitions covers Key Definitions within Pathogens and Disease Transmission for GCSE Biology. Types of pathogens, how diseases spread, transmission methods, and prevention strategies It is section 13 of 18 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 13 of 18
Practice
18 questions
Recall
20 flashcards
Key Definitions
Pathogen: A microorganism that causes disease in a host organism. The four main types are bacteria, viruses, fungi, and protists.
Bacterium (plural: bacteria): A single-celled prokaryotic organism with a cell wall but no membrane-bound nucleus. Some bacteria cause disease by invading tissues and releasing toxins.
Virus: A non-cellular pathogen consisting of genetic material (DNA or RNA) inside a protein coat. Viruses cannot reproduce independently — they must infect and hijack a living host cell.
Vector: An organism (often an insect) that carries and transmits a pathogen from one host to another without being harmed itself. The Anopheles mosquito is the vector for malaria.
Toxin: A poisonous substance produced by a pathogen (especially bacteria) that damages host cells and tissues, causing symptoms of disease.
Transmission: The process by which a pathogen passes from one host to another. Routes include airborne droplets, direct contact, contaminated food/water, and vector transmission.
Antibiotic: A chemical that kills or inhibits the growth of bacteria. Antibiotics are ineffective against viruses because viruses lack the cellular structures (such as cell walls) that antibiotics target.
Infectious dose: The minimum number of pathogen particles or cells required to establish an infection in a host organism.