Helical

Definition

Helical refers to the spiral shape of some viral capsids, which are composed of protein subunits that form a cylindrical structure. This shape allows for efficient packaging of the viral genome.

5 Must Know Facts For Your Next Test

1. Helical viruses have a capsid with a rod-shaped structure formed by repeated protein units.
2. The helical structure can be rigid or flexible, depending on the virus.
3. Examples of helical viruses include the Tobacco Mosaic Virus (TMV) and Influenza viruses.
4. The helical symmetry allows for efficient packaging and protection of the viral RNA or DNA.
5. In enveloped helical viruses, the capsid is surrounded by a lipid envelope derived from the host cell membrane.

Review Questions

• What structural feature characterizes helical viruses?
• Name two examples of helical viruses.
• How does the helical symmetry benefit the virus in terms of genome packaging?

Related terms

Capsid: The protein shell surrounding and protecting the viral genome.

Envelope: A lipid bilayer derived from the host cell membrane that surrounds some types of viral capsids.

Symmetry: The spatial arrangement of proteins in a virus particle, including helical and icosahedral forms.