What is a pathogen?
An organism that causes disease.
Cambridge IGCSE (9–1) Biology 0970 (Extended) (2026–2028) · 10.1
Revise Cambridge IGCSE (9–1) Biology 0970 (Extended) (2026–2028) specification point 10.1, Diseases and immunity, with free active-recall flashcards. Flip through the set or review every question and answer below.
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What is a pathogen?
An organism that causes disease.
How can a pathogen cause illness after entering a host?
It can reproduce or act in ways that damage the body.
What makes a disease transmissible?
The pathogen causing it can pass from one host to another, allowing the disease to spread through a population.
Are all diseases caused by infectious organisms?
No. Not all diseases are caused by infectious organisms.
What is pathogen transmission?
The transfer of a pathogen from one host to another.
How can pathogens spread through direct contact?
By touching an infected person or exchanging blood or other body fluids.
What makes pathogen transmission indirect?
Something else carries the pathogen before it reaches a new host.
What are four important indirect routes of pathogen transmission?
How does the skin defend the body against pathogens?
It forms a physical barrier that blocks many pathogens from entering.
How do nose hairs and mucus help defend the breathing system?
They trap particles and microorganisms from the air before they reach deeper parts of the breathing system.
How does stomach acid defend the body against pathogens?
It kills many pathogens swallowed in food or water.
How do white blood cells defend the body against pathogens that pass the first barriers?
They attack and destroy the pathogens.
How does a clean water supply reduce disease transmission?
It prevents waterborne pathogens from being drunk or used in the home.
What two risks does hygienic food preparation reduce?
How does good personal hygiene reduce disease transmission?
It lowers the chance of transferring pathogens between people, surfaces and food.
How does waste disposal reduce disease transmission?
It removes rubbish and other materials that could harbour pathogens or attract disease-spreading animals.
How does sewage treatment reduce disease transmission?
It reduces the release of human waste containing pathogens into the environment.
Why do hygiene and public health measures protect whole communities rather than just individuals?
They break transmission pathways, reducing the spread of pathogens through the community.
What type of molecule is an antibody?
A protein.
Why does an antibody bind to a particular antigen rather than to every pathogen?
Its binding site has a shape complementary to that particular antigen's shape.
What are two possible outcomes of an antibody binding to a pathogen's antigen?
What is active immunity?
Defence against a pathogen produced by the body's own immune response.
What stimulates antibody production during active immunity?
Exposure to a pathogen's antigens.
What are the two ways active immunity can develop?
Why does active immunity enable a faster response to a later encounter with the same pathogen?
Memory cells are produced during the immune response.
What does vaccination introduce into the body?
Weakened pathogens or their antigens.
What two things do vaccine antigens stimulate lymphocytes to produce?
Antibodies and memory cells.
How do memory cells formed after vaccination provide long-term immunity?
They allow a response to the pathogen on later exposure.
Why does protecting people from infection through vaccination help control disease spread?
It reduces opportunities for the pathogen to pass between hosts.
What is passive immunity?
Short-term defence provided by antibodies acquired from another individual, rather than produced by the recipient’s own immune response.
By which two routes can antibodies pass from mother to infant?
Why does passive immunity provide only temporary protection?
It does not produce memory cells in the recipient.
What type of pathogen causes cholera?
A bacterium.
How is the bacterium that causes cholera transmitted?
Through contaminated water.
What effect does the toxin produced by cholera bacteria have on the small intestine?
It causes chloride ions to be secreted into the small intestine.
How does chloride ion secretion into the intestine lead to diarrhoea in cholera?
Water moves into the gut by osmosis, causing diarrhoea.
What are the two consequences of losing water and ions from the blood during cholera?