CBSE 2026 · Region 2 · Set 1 · Q28 · 3 marks
(a)A person inhales dust and pathogens but does not always fall sick. Explain how the body protects against such infections.(b)Name and describe any two barriers involved in this protection.
(a)
A person inhales dust and pathogens but does not always fall sick. Explain how the body protects against such infections.
(b)
Name and describe any two barriers involved in this protection.
Marking-scheme solution
(a)
Due to immune response shown by the body / due to ability of the body to fight
against foreign agents (pathogens)
(b)
$\displaystyle \star$ Physical barrier, Skin on our body prevents entry of pathogens / Mucus coating (of respiratory, gastrointestinal, urinogenital tract) help in trapping microbes entering our body.
$\displaystyle \star$ Physiological barrier, Acid from stomach / saliva in the mouth / tears from eyes – all prevent microbial growth.
$\displaystyle \star$ Cellular barrier, Neutrophils and monocytes in the blood as well as macrophages in tissues can phagocytose and destroy microbes.
$\displaystyle \star$ Cytokine barrier, Virus infected cell secrete proteins interferons that protect non-infected cells from further viral infection
(Any Two)
Human Health and DiseaseImmunityUnderstandshort_answermedium
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CBSE Class 12 Biology past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.