Viruses can be defined as infective agents that are made up of nucleic acid enclosed in a protein coat.
Viruses are unable to replicate or multiply without utilizing the host cells' reproductive mechanisms.
Examples are influenza virus, mumps virus, rabies virus, poliovirus, Herpes virus, human immunodeficiency virus (HIV), etc.
Viruses are made up of the following components:
DNA or RNA:
A genome is made up of nucleic acids that can be DNA (like humans) or RNA.
RNA is very similar to DNA both are made up of chains of nucleotides (ACGT/U) that make up genes that are translated into proteins.
Capsid:
The genome is protected by a protein coat called the capsid.
The capsid proteins called capsomeres assemble around the viral genome in different arrangements and are termed either helical (e.g. influenza or coronavirus) or icosahedral and a more complex 20-sided shape (e.g. herpes or norovirus).
Envelope:
Some viruses have an external covering called an envelope, which is derived from the host cell and can take many forms.
Coronaviruses, like SARS-CoV-2, are spherical, the Ebola virus is long and filament shaped.
Enveloped viruses are more susceptible to the destruction of the lipid through the use of soap or alcoholic hand-gels than viruses without lipid envelopes.
