Defence Against DiseaseEdexcel GCSE Biology: Flashcards

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Three physical barriers against pathogens?

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Three physical barriers against pathogens?: Skin, mucus, cilia.
Role of cilia?: Waft mucus and trapped pathogens out of the respiratory tract.
Where are lysozymes found and their role?: Tears and mucus; destroy bacterial cell walls.
Role of hydrochloric acid?: Produced in stomach; kills swallowed pathogens.
What is an antigen?: A foreign molecule on a pathogen's surface recognised by the immune system.
What happens when antigens trigger an immune response?: Lymphocytes produce specific antibodies and memory lymphocytes.
Why is the secondary response faster?: Memory lymphocytes recognise the antigen immediately, producing more antibodies faster.
How does immunisation work?: Inactive pathogen triggers antibody/memory lymphocyte production without causing disease.
One advantage, one disadvantage of immunisation?: Advantage: herd immunity. Disadvantage: mild side effects (rarely severe).
What is herd immunity?: High immunisation rate reduces spread, protecting unvaccinated individuals.
Why can't antibiotics treat viruses?: They inhibit bacterial processes absent in viruses.
Purpose of an autoclave?: Sterilises growth medium and dishes with high-pressure steam.
Why flame a sterile loop before/after use?: Kills contaminating microbes without contamination.
Why keep Petri dishes covered?: Prevents contamination and escape of cultured microbes.
Zone of inhibition diameter 20mm, calculate area.: Radius=10mm, area=π×10²=314.2mm².