Infection & ResponseDefinitions

Key Definitions

Part of Pathogens and Disease Transmission · GCSE GCSE Biology revision

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 14 of 19 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.

Topic position

Section 14 of 19

Practice

24 questions

Recall

21 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.

Keep building this topic

Read this section alongside the surrounding pages in Pathogens and Disease Transmission. That gives you the full topic sequence instead of a single isolated revision point.

How It Works: How Pathogens Cause Disease Common Misconceptions The Invisible Enemy Key Facts: Pathogens

Practice Questions for Pathogens and Disease Transmission

What is a pathogen?

A. A microorganism that causes disease
B. A type of white blood cell
C. An antibody produced by the immune system
D. A nutrient required for growth

1 markfoundation

Explain why viruses need to infect host cells in order to reproduce.

3 marksstandard

Quick Recall Flashcards

What is direct transmission?

When pathogens are passed directly from one person to another through physical contact

What is a pathogen?

A microorganism that causes disease in living organisms

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How It Works: How Pathogens Cause Disease

Common Misconceptions