A viral envelope is primarily made of a lipid bilayer and viral glycoproteins.
Here's a more detailed breakdown:
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Lipid Bilayer: This is a fatty membrane similar to the membranes surrounding our own cells. The virus obtains this bilayer from the host cell during the budding process. As the virus exits the host cell, it essentially steals a piece of the cell's membrane, which then becomes its envelope.
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Viral Glycoproteins: These are proteins encoded by the virus itself and are embedded within the lipid bilayer. "Glyco-" refers to the fact that these proteins have sugar molecules attached to them (glycosylation). These glycoproteins play crucial roles in:
- Attachment: They help the virus bind to and enter new host cells. They act like keys that fit specific receptors on the surface of host cells.
- Fusion: Some glycoproteins mediate the fusion of the viral envelope with the host cell membrane, allowing the virus to enter the cell.
- Immune Evasion: The glycans (sugar molecules) can sometimes help shield the virus from the host's immune system.
In summary, a viral envelope is a structure composed of host-derived lipids and virus-encoded glycoproteins that surrounds the viral capsid, providing protection and enabling entry into host cells.
