The protective protein shell formed by viral coat proteins is called

The protective protein shell formed by viral coat proteins is called

• A. Capsid
• B. Capsule
• C. Envelope
• D. Nucleoid

Answer: (A)

The protective protein shell around a virus’s genome is called the capsid. It’s built from repeating protein subunits (capsomeres) that assemble into a sturdy shell, often with icosahedral or helical shapes, to safeguard the viral nucleic acid from damage and help with delivering it to a new host cell. Some viruses have an additional outer lipid layer called an envelope, derived from the host cell membrane, but this envelope is separate from the protein coat itself. The term capsule refers to a bacterial polysaccharide layer outside the cell, not to viral coats, and the nucleoid is the region where a bacterial chromosome resides—neither describes the viral protein shell.

The protective protein shell around a virus’s genome is called the capsid. It’s built from repeating protein subunits (capsomeres) that assemble into a sturdy shell, often with icosahedral or helical shapes, to safeguard the viral nucleic acid from damage and help with delivering it to a new host cell. Some viruses have an additional outer lipid layer called an envelope, derived from the host cell membrane, but this envelope is separate from the protein coat itself. The term capsule refers to a bacterial polysaccharide layer outside the cell, not to viral coats, and the nucleoid is the region where a bacterial chromosome resides—neither describes the viral protein shell.