Difference between Virus and Virion

The difference between virus and virion is that virus is the nucleoprotein particle whereas virion is the active, infectious form of the virus. A virus consists of genetic material encased by a protein capsid. It does not show any metabolic activity. Virion is the vector stage of a virus, which permits the transmission of a virus from one infected host cell to another.

Therefore, the virus is the intracellular phase whereas virion is the extracellular phase of the virus. Both virus and virion are two kinds of microscopic, obligatory parasites that are infectious. In this article, we will study the difference between a virus and a virion, what a virus is, the characteristics of a virus, what a virion is, and the similarities between a virus and virion.

Difference Between Virus and Virion

The table below highlights the differences between virus and virion:

Features	Virus	Virion
Definition	Virus is a small parasite that consists of a nucleic acid molecule covered by a protein coat.	Virion is the complete, infective form of a virus outside the host cell. They consist of both nucleic acid and protein layers.
Significance	Virus is a nucleoprotein particle and a non-cellular entity.	Virion is the infectious form of a virus.
Intracellular/Extracellular	Virus is the intracellular parasite.	Virion is the extracellular parasite.
Size	Virus is comparatively larger than a virion.	Virion is smaller than the virus.
Shape	The shapes of a virus are helical, icosahedral, prolate, envelope, and complex.	Most virions are spheroidal or rod-shaped.

What is a Virus?

A virus is a minute, non-cellular structure comprising of a nucleic acid molecule covered by a protein coat. It is an intracellular parasite. It has the ability to proliferate and invade the living cells of plants, animals, and other microorganisms; however, it can only replicate itself within a particular host cell. A virus particle typically consists of a single-stranded or double-stranded, DNA or RNA genome, covered by a protein coat called capsid. Viruses have various sizes spanning from 10–400 nm in diameter.

They are considered to be non-living entities when outside the host cell as they do not show any metabolic activity. As such, they belong to a unique category that cannot be distinctly classified as either living or non-living. A virus is comparatively larger than a virion and may have different shapes. It can be helical, prolate, envelope, complex or icosahedral among others.

Characteristics of Viruses

Following are a few characteristic of viruses:

• A cell nucleus is absent.
• Their cell structure is disorganized.
• They usually consist of one or two strands of DNA or RNA.
• They are covered in a protective protein coat called capsid.
• They are able to reproduce even though they cannot grow, respire, or metabolize.
• They are considered both living and non-living since they are inactive outside the host cell and become active within the host cell.

What is a Virion?

A virion is not the same as a virus but it is a virus in its extracellular phase. It is the complete, active, infectious form of a virus that exists outside the host cell. It is an extracellular parasite. It is composed of either a DNA or RNA genome, and is encased in an outer protein shell termed as capsid. It also contains an additional outer membrane made up of lipids called the envelope.

Virion is relatively smaller than the virus and is typically spheroidal in shape. The majority of plant viruses have rod-shaped virions. Virions perform the function of securely transporting the virus from the original host to a new host. Additionally, they also protect the genetic material from external threats.

Similarities Between Virus and Virion

Following are the similarities between virus and virion:

• The genetic material of both viruses and viron is made up of DNA or RNA.
• A protein coat envelops both virion and virus.
• Virion and viruses are both self-replicating entities.
• Both virus and virion are non-cellular entities that are host specific.
• Both virus and virion exhibit lower levels of metabolic activity.

Conclusion: Difference between Virus and Virion

A virus is a broader term that encompasses the entire infectious agent, including its various stages of the life cycle (inside and outside the host cell). On the other hand, a virion specifically refers to the extracellular, infectious form of a virus, which is the particle responsible for initiating new infections.

FAQs on Virus and Virion

Is a Virion the Same as a Virus?

No, a virion is not the same as a virus, but the two terms are closely related. A virus is the entire infectious agent, while a virion is a specific form of the virus, representing the particle that can infect a host cell.

Why are Virions not Cells?

Virions are not considered cells because they lack the essential characteristics that define living cells and also due to their dependence on host cells for essential life processes.

Is the Virion the Nucleic acid of a Virus?

No, the virion refers to the complete, infectious viral particle and includes both the nucleic acid and the protein coat (capsid) that encases it.

Can a Virion have both DNA and RNA?

A virion generally contains either DNA or RNA, but not both. Based on the type of genetic material they carry, they are broadly categorized as DNA viruses or RNA viruses.

What is the Difference between Virion and Viroid?

Virions are complete viral particles with genetic material and a protein coat, infecting a wide range of organisms. Viroids, on the other hand, are small RNA molecules that specifically infect plants and do not have a protein coat.