Viruses share a protein capsid enclosing nucleic acid, lack cellular machinery, and can reproduce only by exploiting the metabolism of a living host cell.
Coverage 2021–2025 · Updated 15 Jul 2026
Viruses contain genetic material enclosed in a protein coat, and many also have a lipid envelope with attachment proteins.
The genome stores instructions for making viral components; the capsid protects it and helps deliver it into a host cell. Envelopes are host-derived membranes carrying viral proteins that recognize receptors.
Describe a virus structurally:
An enveloped virus may bind a host receptor with a spike protein, fuse membranes, and release its genome into the cytoplasm.
A virus particle has structure but lacks the complete machinery for independent metabolism and protein synthesis.
This objective is assessed through structured response, commonly using State / Label / Describe.
State / Label / Describe / Justify
Build the answer around this relationship: Every virus has genetic material enclosed by a protein capsid.
Describing viruses as cells that merely lack a nucleus instead of recognizing that they are acellular.
Representative question
Describe one reason that viruses are not considered to be living.
A strong HL virus answer usually combines two moves: define the boundary, then explain the mechanism or consequence. Viruses have DNA or RNA plus a capsid but lack the machinery for independent metabolism. Their diversity is described by genome, capsid, and envelope. Lambda phage lets you contrast lytic takeover with lysogenic integration. Origin questions require competing hypotheses and polyphyly. Evolution questions require mutation, recombination, short cycles, large populations, and examples such as influenza or HIV.
