Biology – Cells as the basic units of living organisms | e-Consult
Cells as the basic units of living organisms (1 questions)
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All viruses are non-cellular, meaning they are not composed of cells. Their basic structure consists of a nucleic acid core, which can be either DNA or RNA, and a protein coat called a capsid. The capsid protects the nucleic acid. Some viruses possess an additional outer layer called an envelope, which is derived from the host cell membrane during viral replication.
The presence of an envelope provides several advantages:
- Protection: The envelope protects the viral capsid and nucleic acid from enzymatic degradation in the extracellular environment. This allows the virus to survive longer outside of a host cell.
- Attachment: Viral glycoproteins embedded in the envelope mediate attachment to specific receptors on the host cell surface. This is crucial for initiating infection.
- Entry: The envelope facilitates entry into the host cell. The envelope can fuse with the host cell membrane, releasing the viral capsid and nucleic acid into the cytoplasm.