A capsomer is a protein subunit that interlocks with other capsomeres to form the closely packed capsid of a virus. Each capsomer is made of one or more different types of capsomere proteins.

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Structures associated with Animal Viruses include: 

- Capsid
- Capsomer
- Viral lipid envelope
- Spike proteins

Animal Virus Structures

The structural components of a typical bacteriophage include a head region consisting of a protein capsid that encloses the viral genome, a neck-like sheath, and tail fibers that resemble spider-like legs used to attach to the host cell.

Bacteriophage Structures

A capsid is a protein coat that encloses a virus's genetic material. Unlike a cellular interior filled with cytosol, the inside of a capsid contains only the essential genome and enzymes required to direct the synthesis of new virions.

Capsid

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Viral spikes are protein structures that extend outward from the capsid on some naked and enveloped viruses. They function to attach the virus to host cells and determine the viral host range.

Viral Spikes

Capsomer

A viral envelope is a lipid layer that surrounds the capsid of some viruses, consisting of a portion of host-cell phospholipid membrane acquired as the virion buds. The envelope can originate from either cytoplasmic or intracellular membranes of the host cell.

Viral envelope

Connects the polyhedral head to the tail fibers and tail pins

Sheath

Helps with viral attachment to the receptors of the host cell surface for entry

Tail fibers/pins

Bacteriophage replication can proceed through two main pathways: the lytic cycle, which involves replicating viral parts, assembling them into virions, and lysing the host cell to release them; and the lysogenic cycle, where the viral DNA integrates into the host chromosome as a prophage and replicates alongside it, potentially excising itself to enter the lytic cycle under stress.

Bacteriophage Replication Cycles

Viruses differ in the shape of their capsids. Some capsid shapes include:
- Helical
- Icosahedral
- Complex

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