Final answer:
An enveloped virus has a membranous layer, known as a viral envelope, external to the nucleocapsid, derived from the host cell's membrane and aiding in the infection process.
Step-by-step explanation:
A enveloped virus is an individual virus particle outside a host cell that consists of a nucleic acid core, an outer protein coating, and a membranous layer external to the nucleocapsid. This viral envelope is obtained as the virion buds from a host cell and is composed of phospholipid membranes derived from the host cell. It is studded with proteins coded for by both the viral genome and the host genome.
An enveloped virus gains an outer lipid bilayer, known as a viral envelope, which includes proteins that may be coded for by both the viral and host genomes. This envelope can come from the host cell's outer membrane or internal membranes such as the nuclear membrane or endoplasmic reticulum. The lipid membrane and any carbohydrates present in the envelope are derived entirely from the host cell. Several well-known examples of enveloped viruses are the influenza virus, HIV, and the varicella zoster virus. By having an envelope, these viruses are able to fuse with host cells and initiate infection by releasing their genetic material.