Most viruses have either a helical or icosahedral structure. However, some viruses exhibit more complex shapes.
Common Viral Shapes:
- Helical: Resembling a spiral or a long rod. Think of a tightly coiled spring.
- Icosahedral: A geometric shape with 20 triangular faces. Imagine a soccer ball.
Complex Viruses:
A significant number of viruses don't neatly fit into the helical or icosahedral categories. These viruses have complex structures, often combining elements of both helical and icosahedral forms. Examples include:
- Poxviruses: These viruses have a complex, brick-like shape.
- Geminiviruses: These viruses have twinned icosahedral particles.
- Many bacteriophages: These viruses, which infect bacteria, often possess a polyhedral "head" attached to a helical "tail."
Examples of Viral Shapes:
- Varicella-zoster virus (VZV): This virus, which causes chickenpox and shingles, has an icosahedral capsid, meaning it's shaped like a sphere. [Source: Varicella zoster virus | HARTMANN SCIENCE CENTER, Pathogen Safety Data Sheets: Infectious Substances – Varicella ...]
- Influenza virus: While generally described as having a rounded shape, its form can be elongated or irregular. It's characterized by spikes projecting from its surface. [Source: Influenza Virus (Flu)]
- SARS-CoV-2 (the virus causing COVID-19): Research has produced detailed images of its structure, revealing features important for vaccine and treatment development. [Source: Novel coronavirus structure reveals targets for vaccines and ...]
The shape of a virus is determined by the arrangement of its protein coat (capsid) and its genetic material (either DNA or RNA). The specific shape is crucial for the virus's ability to infect host cells.
The provided text mentions that viruses are small, obligate intracellular parasites with DNA or RNA genomes. [Source: Virus Structure and Classification - PMC] The size of viruses varies greatly, generally ranging from 5 to 300 nanometers. [Source: 10.2: Size and Shapes of Viruses - Biology LibreTexts] The nucleic acid and proteins within each virus assemble into a structure called a nucleoprotein or nucleocapsid. [Source: Virus - Structure, Capsid, Genome | Britannica]
