Q.7 In viruses, capsids are made up of
(A) proteins (B) nucleic acids (C) lipids (D) sterols
Capsids in viruses are protein structures that protect the genetic material. The correct answer is (A) proteins.
Option Analysis
Capsids form the outer protein shell of a virus, enclosing nucleic acids like DNA or RNA. Option (A) proteins is accurate, as capsids consist of repeating protein subunits called capsomeres or protomers that self-assemble into icosahedral, helical, or complex shapes. Option (B) nucleic acids is incorrect, since nucleic acids serve as the genome inside the capsid, not its building block. Option (C) lipids applies to viral envelopes in some viruses, which derive from host membranes but surround the capsid rather than composing it. Option (D) sterols is wrong, as sterols like cholesterol appear in envelopes for stability but not in capsids.
Virus capsids made up of proteins serve as the essential protective shell enclosing the viral genome in all viruses. This protein-based structure ensures safe delivery of nucleic acids into host cells, a core concept in virology for exams like CSIR NET Life Sciences.
Capsid Composition Explained
Virus capsids made up of proteins consist of capsomeres, which are clusters of protomers—identical or varied polypeptide chains. These self-assemble symmetrically to minimize genetic coding needs while maximizing protection against environmental damage. Nucleic acids reside inside, lipids form optional envelopes, and sterols play no direct role.
Functions and Shapes
Capsids protect genetic material, aid host attachment, and enable genome release post-infection. Common shapes include icosahedral (e.g., adenovirus), helical (e.g., tobacco mosaic virus), and complex (e.g., bacteriophages). In replication, host machinery synthesizes new protein subunits for fresh capsids.
Exam Relevance
For competitive exams, remember: capsids are always protein-based, distinguishing naked from enveloped viruses. Practice MCQs like “In viruses, capsids are made up of (A) proteins” to master this.
