Virus composition — What are the two fundamental components found in all complete virions (across diverse families)?

Introduction / Context:
Despite their vast diversity, all viruses share a minimal structural plan: a genome packaged by a protective protein shell. Understanding this universal blueprint helps differentiate essential elements from optional features like envelopes.

Given Data / Assumptions:

• “Complete virion” means an infectious particle.
• Viral genomes may be DNA or RNA (single-stranded or double-stranded, segmented or non-segmented).
• The protein shell (capsid) provides protection and facilitates delivery to host cells.

Concept / Approach:
The minimal viral unit contains nucleic acid (genetic material) and capsid protein. Some viruses additionally acquire a host-derived lipid envelope containing viral glycoproteins, but envelopes are not universal. Carbohydrates may decorate glycoproteins but are not obligatory. Thus, among offered pairs, only “nucleic acid and protein” is universally required.

Step-by-Step Solution:

Verification / Alternative check:
Non-enveloped viruses (e.g., adenovirus, picornavirus) demonstrate infectivity with only nucleic acid and capsid proteins, confirming that lipids and polysaccharides are not universal requirements.

Why Other Options Are Wrong:

• Fat and protein: lipids are absent in many non-enveloped viruses.
• Carbohydrate and nucleic acid: no universal carbohydrate component.
• Fat and carbohydrate: omits the essential capsid protein and genome pairing.

Common Pitfalls:
Assuming all viruses are enveloped; many clinically important viruses lack envelopes entirely.

Final Answer:
nucleic acid and protein