• Discovery of Viruses
• Introduction to Viruses
• Structure of Viruses
• Classification of Viruses
• Viral Disease
For the complete syllabus, check out our PMDC MDCAT Syllabus 2025 article.
Genome: the genetic material, either DNA or RNA. The DNA or RNA may be single-stranded or double-stranded.
Capsid: a protective coat of protein surrounding the core built up of identical repeating subunits called capsomeres.
Nucleocapsid: the combined structure formed by the core and capsid.
Envelope: a few viruses, such as the HIV and influenza viruses, have an additional bilayer membrane plus glycoproteins, a membranous layer around the capsid derived from the cell surface membrane of the host cell. The adhesion properties are determined by those proteins that make up the coat and envelopes.
The envelope is very sensitive to heat, detergents, and desiccation; thus, enveloped viruses are easier to kill.
Structure of Viruse
Protective Shell – Capsid
- Made of many identical protein subunits
- Protects the genetic material
- May be involved in cell entry
- Symmetrically organized
- Comprises 50% of the virus's weight
- Can be either enveloped or non-enveloped
Envelope
- A lipid-containing membrane that surrounds some virus particles
- Located outside the capsid
- Acquired during viral maturation
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