Question

A virus containing only nucleic acid and a capsid is called a/an __________ virus or ___________ virus.

Short answer

naked virus or non-enveloped virus

Step-by-step solution

- Identify virus characteristics

Determine the basic characteristics of the virus described. The virus contains only nucleic acid and a capsid, meaning it lacks other components such as an envelope.

- Define virus type

A virus that lacks an envelope and contains only nucleic acid and a capsid is classified as a 'naked' virus.

- Confirm the terminology

Ensure the terminology used matches the virus description. A virus with only nucleic acid and a capsid is also known as a 'non-enveloped' virus.

Key concepts

Virus Structure

A virus is a tiny microorganism that can infect living organisms and replicate within them. Viruses are unique because they cannot reproduce on their own; they need a host cell to do so. The structure of a virus is relatively simple, especially when compared to cells.
Most viruses contain two main components:

• Nucleic Acid: The genetic material of the virus, which can be either DNA or RNA.
• Capsid: A protein shell that surrounds and protects the nucleic acid.

Some viruses also have an additional outer layer called an envelope, which is derived from the host cell membrane. However, in 'naked' viruses, this envelope is absent. Understanding these components helps in studying how viruses infect cells and how they can be targeted by treatments.

Nucleic Acid

The nucleic acid in a virus is the blueprint that contains all the genetic information necessary for the virus to replicate. This genetic material can be:

• DNA (Deoxyribonucleic Acid)
• RNA (Ribonucleic Acid)

Depending on the type of virus, the nucleic acid can be single-stranded or double-stranded, and it can be linear or circular in shape. The nucleic acid is crucial because it codes for the production of viral proteins once inside a host cell.
During infection, the nucleic acid is injected into the host cell, where it hijacks the cell's machinery to produce more viral particles. This process is key to the virus's ability to propagate and cause disease.

Capsid

The capsid is the protein shell that encases the viral nucleic acid. It serves several important functions:

• Protection: It safeguards the nucleic acid from degradation by enzymes and harsh environmental conditions.
• Attachment: It helps the virus attach to host cells via specific receptor interactions.
• Entry: It can facilitate the entry of nucleic acid into the host cell.

The capsid is composed of protein subunits called capsomeres, which assemble in a highly organized manner. These can form various shapes, including:

• Icosahedral: A symmetrical structure with equilateral triangles, providing strong protection.
• Helical: A spiral arrangement around the nucleic acid, common in RNA viruses.
• Complex: Irregular shapes that combine features of both icosahedral and helical structures.

In naked viruses, the capsid plays an essential role as it's the primary barrier protecting the viral genetic material, due to the absence of an outer envelope.