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AQASpec 4.3.1Foundation & Higher~30 min

Communicable Diseases

Biology · Topic revision workspace

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Topic overview

What you need to know

Communicable Diseases is a key part of GCSE Biology. Connect structures to their functions and explain biological processes as clear causal sequences. A microorganism that causes disease. Includes bacteria, viruses, fungi, and protists. Single-celled prokaryotic organisms that cause disease by releasing toxins. Treated with antibiotics. E.g. Salmonella. A non-living particle that reproduces inside host cells, damaging them. Much smaller than bacteria. E.g. HIV, measles.

Exam tip

Use precise scientific vocabulary and make each link in an explanation explicit.

Revision notes

Core ideas

Secure these ideas first. Say each definition in your own words, then connect it to the topic overview.

  • Pathogen: A microorganism that causes disease. Includes bacteria, viruses, fungi, and protists.
  • Bacteria: Single-celled prokaryotic organisms that cause disease by releasing toxins. Treated with antibiotics. E.g. Salmonella.
  • Virus: A non-living particle that reproduces inside host cells, damaging them. Much smaller than bacteria. E.g. HIV, measles.
  • White Blood Cells: Immune cells that defend the body: phagocytes engulf pathogens, lymphocytes produce antibodies and antitoxins.

Revision notes

Apply it in the exam

The exam will rarely ask for an isolated definition. Practise selecting the right idea and using it as part of a complete explanation or method.

  • Antibody: A protein produced by lymphocytes that is specific to a particular antigen on a pathogen. Locks onto the pathogen to destroy it.
  • Vaccination: Injecting a dead or weakened form of a pathogen to stimulate the immune system to produce antibodies, creating memory cells.
  • Antibiotic: A medicine that kills bacteria or stops their growth inside the body. Antibiotics do NOT work on viruses.
  • Antibiotic Resistance: When bacteria evolve and are no longer killed by antibiotics due to natural selection. E.g. MRSA.

Core knowledge

Key facts for Communicable Diseases

1

Pathogen

A microorganism that causes disease. Includes bacteria, viruses, fungi, and protists.

2

Bacteria

Single-celled prokaryotic organisms that cause disease by releasing toxins. Treated with antibiotics. E.g. Salmonella.

3

Virus

A non-living particle that reproduces inside host cells, damaging them. Much smaller than bacteria. E.g. HIV, measles.

4

White Blood Cells

Immune cells that defend the body: phagocytes engulf pathogens, lymphocytes produce antibodies and antitoxins.

5

Antibody

A protein produced by lymphocytes that is specific to a particular antigen on a pathogen. Locks onto the pathogen to destroy it.

6

Vaccination

Injecting a dead or weakened form of a pathogen to stimulate the immune system to produce antibodies, creating memory cells.

7

Antibiotic

A medicine that kills bacteria or stops their growth inside the body. Antibiotics do NOT work on viruses.

8

Antibiotic Resistance

When bacteria evolve and are no longer killed by antibiotics due to natural selection. E.g. MRSA.

Active recall

Close the notes and answer these

  1. 1.Without looking, explain pathogen and give one example or consequence.
  2. 2.Without looking, explain bacteria and give one example or consequence.
  3. 3.Without looking, explain virus and give one example or consequence.
  4. 4.Without looking, explain white blood cells and give one example or consequence.

Content reviewed 23 July 2026 against the current linked specification.

Finished learning?

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