Question

A virus obtains its envelope during which of the following phases? a. attachment b. penetration c. assembly d. release

Short answer

d. release

Step-by-step solution

Understanding the Question

Identify which phase of the viral replication cycle involves the virus obtaining its envelope.

Analyze Each Option

Evaluate each option to see if it matches the phase where the virus gets its envelope.- **Attachment**: The virus binds to the host cell's surface.- **Penetration**: The virus enters the host cell.- **Assembly**: New viral components are put together.- **Release**: New viruses are released from the host cell, often obtaining an envelope from the host's cell membrane.

Determine the Correct Phase

The envelope is acquired as the virus leaves the host cell. This commonly occurs during the release phase, where the virus buds off from the host cell, taking a portion of the host cell membrane with it to form its envelope.

Key concepts

virus attachment phase

The attachment phase is the initial step in the viral replication cycle. During this phase, a virus recognizes and binds to a specific receptor on the surface of a host cell. This interaction is highly specific, often compared to a lock-and-key mechanism.

• The virus identifies a receptor on the host cell membrane.
• The viral surface proteins latch on to these receptors.
• This binding is crucial for the virus's entry into the cell.

Without successful attachment, a virus cannot proceed to the next stages of its replication cycle. Examples of viral receptors include the CD4 receptor for HIV and the ACE2 receptor for SARS-CoV-2.

virus penetration phase

Once the virus has successfully attached to its host cell, the next step is penetration. This phase involves the virus entering the host cell to deliver its genetic material. Different viruses employ various methods to achieve this:

• Endocytosis: The host cell engulfs the virus in a vesicle.
• Direct fusion: The viral envelope fuses with the cell membrane, allowing the viral genome to enter the host cell.

The mode of entry can significantly affect how the virus interacts with the host cell and its immune defenses.

virus assembly phase

During the assembly phase, new viral particles are put together inside the host cell. This process involves several steps:

• Replication: The viral genome is replicated.
• Translation: Viral proteins are synthesized using the host's cellular machinery.
• Assembly: The newly formed viral genetic material and proteins are assembled into new viruses.

This phase is essential for the production of multiple viral progeny, which will go on to infect new cells. Proper assembly ensures that each new viral particle is capable of continuing the infection process.

virus release phase

The release phase is the concluding step in the viral replication cycle. In this phase, newly formed viral particles exit the host cell. There are two main methods by which viruses are released:

• Lysis: The host cell bursts, releasing the viruses.
• Budding: The virus acquires its envelope by budding from the host cell membrane, often resulting in the host cell's survival.

As described in the exercise, the envelope is obtained during this release phase through the budding process. The acquired envelope is crucial for some viruses, as it helps them evade the host's immune system and facilitate entry into new host cells.