Regarding viral entry, every virus encodes at least one protein that it uses to infect cells. Is this:

Question

BlackTom AI · Accepted Answer

Viral entry requires at least one virus-encoded protein that mediates attachment and/or penetration into the host cell.

1) Relevant knowledge points and concepts
- Viral entry is a multistep process: attachment to a host-cell receptor, penetration (fusion or endocytosis), and uncoating. 
- Viruses encode structural proteins (envelope glycoproteins or capsid proteins) that bind host receptors and trigger the conformational changes needed for membrane fusion or capsid rearrangement. 
- Examples: influenza hemagglutinin (HA) and neuraminidase; HIV Env (gp120/gp41); SARS-CoV-2 spike protein; adenovirus fiber and penton base; picornavirus capsid protein VP1; bacteriophage tail fibers.

2) Step-by-step reasoning
- Step 1: For a virion to recognize and attach to a cell, something on the virion must interact specifically with a host surface molecule. That “something” is a viral protein (glycoprotein on enveloped viruses, capsid protein on non-enveloped viruses).
- Step 2: After attachment, entry often requires a structural change in that viral protein (e.g., fusion peptides exposed, receptor-mediated endocytosis triggered). Those conformational changes are properties of virus-encoded proteins.
- Step 3: Without a viral protein to bind receptors or mediate fusion/penetration, the virion cannot initiate the entry cascade; host factors alone cannot confer the necessary specificity and mechanics.

3) Calculations
- Not applicable; this is conceptual/molecular biology reasoning.

4) Why the correct answer is correct
- Every characterized virus encodes at least one structural protein that participates in receptor binding and/or membrane penetration. Even the smallest viruses encode capsid proteins that determine tropism and initiate entry events; enveloped viruses encode surface glycoproteins that mediate receptor binding and fusion.

5) Why the other option (false) is incorrect
- Saying “false” would imply some viruses can enter without any virus-encoded entry protein. No known virus lacks such proteins: host proteins may assist, but entry still requires a viral ligand or structural protein. Therefore “false” contradicts established virology.

6) Conclusion
- The statement is true — every virus encodes at least one protein used to infect cells. This matches the provided answer: true.

Regarding viral entry, every virus encodes at least one protein that it uses to infect cells. Is this:Single choice

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