The Viral Life Cycle: The Role of Virions and Replication in Infecting Host Cells

1. virion (waiting) exists outside of host2. infected cell (replication)

A virion is a complete, infectious viral particle that is capable of infecting a host cell

1. Virion (waiting) exists outside of host:

A virion is a complete, infectious viral particle that is capable of infecting a host cell. This stage of the viral life cycle occurs when the virus is outside of its host and is waiting for an opportunity to enter a suitable host cell to initiate infection and replication. The term “virion” specifically refers to the mature form of the virus, which consists of a viral genome (either DNA or RNA) surrounded by a protein coat called the capsid. Some virions also have an outer envelope derived from the host cell’s membrane.

During this stage, virions can be present in various environments including air, water, or on surfaces. They can be transferred from an infected host to a healthy individual through direct contact, respiratory droplets, or contaminated objects.

The key characteristic of a virion is its ability to remain stable and infective outside of the host cell for a certain period of time. This allows the virus to persist in the environment and increases its chances of finding a suitable host cell for further replication.

2. Infected cell (replication):

Once a virion enters a host cell, it undergoes a process called replication, which is the next stage of the viral life cycle. During replication, the virus takes control of the host cell’s machinery and uses it to produce more viral particles.

First, the viral genome is released from the virion and enters the host cell’s cytoplasm or nucleus, depending on the type of virus. The viral genome then hijacks the host cell’s replication machinery, forcing it to start producing the necessary components for viral replication.

If the virus has a DNA genome, it is usually transcribed into messenger RNA (mRNA) molecules, which serve as templates for protein synthesis. These viral proteins include enzymes involved in viral replication and structural proteins that form the viral capsid.

For RNA viruses, their RNA genome can act as mRNA directly or it may require a step of viral RNA synthesis known as replication or transcription. During replication, the host cell’s enzymes or viral proteins encoded by the virus itself produce multiple copies of the viral RNA.

Next, the viral proteins and copies of the viral genome assemble to form new viral particles within the host cell. This is often accompanied by the budding or lysis of the infected cell, depending on the type of virus. Budding involves the new virions being released from the host cell by acquiring a portion of the host cell’s membrane, while lysis involves the host cell bursting open, releasing the virions into the surrounding environment.

The process of replication and production of new viral particles within the infected cell can lead to the destruction of the host cell. As a result, the release of new virions from the infected cell allows the virus to spread and initiate infection in other cells, perpetuating the viral life cycle.

More Answers: