10.1

Diseases and immunity

Cambridge IGCSE Biology (0610)  · Unit 10: Diseases and immunity  · 12 flashcards

Diseases and immunity is topic 10.1 in the Cambridge IGCSE Biology (0610) syllabus , positioned in Unit 10 — Diseases and immunity .  In one line: A pathogen is a disease-causing organism. Examples include bacteria (like *Vibrio cholerae* causing cholera), viruses (like influenza), fungi (like athlete's foot), and protozoa (like *Plasmodium* causing malaria).

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical). Past papers from 2022 to 2025 show this topic across 14 questions worth 170 marks (around 2.5% of all Biology marks in those years).

The deck below contains 12 flashcards — 5 definitions, 3 key concepts, 2 process cards and 2 application cards — covering the precise wording mark schemes reward.  Use the 5 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

A pathogen

A pathogen is a disease-causing organism. Examples include bacteria (like *Vibrio cholerae* causing cholera), viruses (like influenza), fungi (like athlete's foot), and protozoa (like *Plasmodium* causing malaria).

What the Cambridge 0610 syllabus says

2026-2028 syllabus, in our words

What the syllabus expects you to be able to do in this topic, in plain English. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks. For the exact wording, see the official syllabus (PDF).

  1. Describe Describe a pathogen as an organism that causes disease.
  2. Describe Describe a transmissible disease as one where the pathogen is able to spread between hosts, passing from one to another.
  3. State State the two routes by which pathogens are transmitted: (a) direct contact, including via body fluids such as blood; (b) indirect, including via air, food, animals and contaminated surfaces.
  4. Describe Describe the body's defences, covering only: skin, mucus, nose hairs, white blood cells and stomach acid.
  5. Explain Explain why each of these helps control how disease spreads: (a) clean water supplies; (b) preparing food hygienically; (c) good personal hygiene; (d) getting rid of waste; (e) treating sewage (the stages of treatment are not needed).
  6. Describe Describe active immunity as protection against a pathogen through the body making its own antibodies. Supplement
  7. State State that every pathogen carries its own antigens, and these have specific shapes. Supplement
  8. Describe Describe antibodies as proteins that lock onto antigens; once attached, they either destroy the pathogen themselves or tag it so that phagocytes destroy it. Supplement
  9. State State that a specific antibody has a shape complementary to, and fitting, a specific antigen. Supplement
  10. Explain Explain that a person gains active immunity either from vaccination or after a pathogen has infected them. Supplement
  11. Outline Outline how vaccination works: (a) weakened pathogens, or their antigens, are introduced into the body; (b) these antigens trigger an immune response in which lymphocytes make antibodies; (c) memory cells form, giving immunity that lasts a long time. Supplement
  12. Explain Explain how vaccination helps to control the spread of diseases. Supplement
  13. Explain Explain that passive immunity is short-term protection against a pathogen from antibodies made by another person, and that it covers both antibodies crossing the placenta and antibodies in breast milk. Supplement
  14. Explain Explain why breast-feeding matters for infants developing passive immunity. Supplement
  15. State State that passive immunity does not produce memory cells. Supplement
  16. Describe Describe cholera as a bacterial disease that is spread through contaminated water. Supplement
  17. Explain Explain how cholera causes harm: the toxin the bacterium releases triggers chloride ions to pass out into the small intestine; water then moves into the gut by osmosis, leading to diarrhoea, dehydration and loss of ions from the blood. Supplement
Definition Flip

Define a pathogen.

Answer Flip

A pathogen is a disease-causing organism. Examples include bacteria (like *Vibrio cholerae* causing cholera), viruses (like influenza), fungi (like athlete's foot), and protozoa (like *Plasmodium* causing malaria).

Definition Flip

What is a transmissible disease?

Answer Flip

A transmissible disease is a disease in which the pathogen can be passed from one host to another. Examples include influenza, cholera, and athlete's foot. These diseases are spread through various means from an infected individual to a healthy one.

Key Concept Flip

List three ways a pathogen can be transmitted indirectly.

Answer Flip

Pathogens can be transmitted indirectly through contaminated surfaces (

Example: touching a doorknob with flu virus), food (. *Salmonella* in undercooked chicken), animals (. mosquitoes carrying malaria), and air (. droplets containing cold viruses).
Key Concept Flip

Describe the role of skin in body defense.

Answer Flip

Skin acts as a physical barrier, preventing pathogens from entering the body. It also produces oils and sweat which can inhibit the growth of some pathogens.

Example: the epidermis layer provides a tough, waterproof barrier.
Key Concept Flip

Explain the importance of a clean water supply in controlling disease spread.

Answer Flip

A clean water supply prevents the spread of waterborne diseases like cholera, caused by the bacterium *Vibrio cholerae*. Ensuring water is free from pathogens reduces the risk of ingestion and subsequent infection.

Definition Flip

Define active immunity.

Answer Flip

Active immunity is a defence against a pathogen by antibody production in the body. It can occur after natural infection or through vaccination, resulting in long-term protection. An example is the body producing antibodies after contracting measles.

Definition Flip

What are antigens, and what role do they play in immunity?

Answer Flip

Antigens are molecules, often proteins, on the surface of pathogens, which have specific shapes. These shapes trigger an immune response, leading to antibody production.

Example: the influenza virus has antigens that trigger the immune system.
Key Concept Flip

Explain how antibodies work to fight pathogens.

Answer Flip

Antibodies are proteins that bind to specific antigens on pathogens. This binding can directly destroy pathogens or mark them for destruction by phagocytes (white blood cells). Each antibody has a shape complementary to the shape of its antigen.

Key Concept Flip

Outline the process of vaccination.

Answer Flip

Vaccination involves introducing weakened pathogens or their antigens into the body. This stimulates lymphocytes to produce antibodies and memory cells, providing long-term immunity without causing the disease. An example is the MMR vaccine against measles, mumps, and rubella.

Definition Flip

What is passive immunity, and how is it acquired?

Answer Flip

Passive immunity is a short-term defence against a pathogen by antibodies acquired from another individual. This can occur across the placenta from mother to fetus or through breast milk.

Example: a newborn baby receives antibodies from breast milk, protecting it from certain infections.
Key Concept Flip

Why is breastfeeding important for infant immunity?

Answer Flip

Breastfeeding provides infants with passive immunity by transferring antibodies from the mother's milk to the baby. These antibodies protect the infant from infections during the first few months of life.

Example: IgA antibodies in breast milk protect against gut infections.
Key Concept Flip

Explain how *Vibrio cholerae* causes diarrhoea and dehydration.

Answer Flip

The *Vibrio cholerae* bacterium produces a toxin that causes chloride ions to be secreted into the small intestine. This leads to osmotic movement of water into the gut, causing diarrhoea, dehydration, and loss of ions from the blood.

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Key Questions: Diseases and immunity

Define a pathogen.

A pathogen is a disease-causing organism. Examples include bacteria (like *Vibrio cholerae* causing cholera), viruses (like influenza), fungi (like athlete's foot), and protozoa (like *Plasmodium* causing malaria).

What is a transmissible disease?

A transmissible disease is a disease in which the pathogen can be passed from one host to another. Examples include influenza, cholera, and athlete's foot. These diseases are spread through various means from an infected individual to a healthy one.

Define active immunity.

Active immunity is a defence against a pathogen by antibody production in the body. It can occur after natural infection or through vaccination, resulting in long-term protection. An example is the body producing antibodies after contracting measles.

What are antigens, and what role do they play in immunity?

Antigens are molecules, often proteins, on the surface of pathogens, which have specific shapes. These shapes trigger an immune response, leading to antibody production.

Example: the influenza virus has antigens that trigger the immune system.
What is passive immunity, and how is it acquired?

Passive immunity is a short-term defence against a pathogen by antibodies acquired from another individual. This can occur across the placenta from mother to fetus or through breast milk.

Example: a newborn baby receives antibodies from breast milk, protecting it from certain infections.

Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0610 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

pathogen disease bacteria virus fungus protoctist transmission infection immune system antibody antigen lymphocyte phagocyte vaccination vaccine immunity active immunity passive immunity HIV AIDS cholera malaria tuberculosis measles

Key terms covered in this Diseases and immunity deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

A pathogen
Transmissible disease
Active immunity
Antigens, and what role do they play in immunity
Passive immunity, and how is it acquired

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