A structural component that is found in all viruses is:
**Core Concept**
Viruses are obligate parasites that require a host cell to replicate and express their genetic material. A structural component common to all viruses is essential for their survival and replication.
**Why the Correct Answer is Right**
The correct answer is a protein that forms a shell around the viral genome, protecting it from the environment and facilitating entry into host cells. This protein is synthesized by the host cell's ribosomes using the viral genome's messenger RNA as a template. The protein shell is composed of multiple subunits that assemble to form a stable structure, which is essential for viral survival and transmission.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it refers to a component found in some viruses, but not all. The correct answer is a universal feature of all viruses.
**Option B:** This option is incorrect because it refers to a viral enzyme involved in replication, but not a structural component.
**Option C:** This option is incorrect because it refers to a host cell component, not a viral component.
**Clinical Pearl / High-Yield Fact**
All viruses have a protein shell that protects their genetic material, and this shell is essential for viral survival and transmission. This is a critical concept in virology, as understanding the structure and function of viral proteins can inform the development of antiviral therapies.
**Correct Answer: C. Capsid**