Microbiology Practice Exam

The envelope of some viruses is indeed constituted primarily by phospholipids derived from the host cell membrane. When a virus buds off from a host cell, it acquires a portion of the host's lipid bilayer, which forms the viral envelope. This envelope can also contain viral proteins, which play critical roles in the virus's ability to infect new host cells and evade the host's immune response.

Understanding the composition of viral envelopes helps explain why some viruses are more adept at infecting certain types of cells. The presence of host-derived phospholipids can facilitate the recognition and binding to specific receptors on target cells.

The other options, while related to viral biology, do not constitute the envelope. Viral protein components are typically embedded within the envelope rather than forming it independently. Carbohydrates found on the host cell do play roles in cell recognition but are not a structural part of the viral envelope. Finally, viral DNA is not involved in forming the envelope; instead, it serves as the genetic material housed within the virus.