Virus: Perbedaan antara revisi

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These structures can range in size from less than 20 nanometers up to 400 nanometers and are composed of viral proteins arranged with [[icosahedral]] symmetry. Icosahedral architecture is the same principle employed by R. Buckminster-Fuller in his [[geodesic dome]], and it is the most efficient way of creating an enclosed robust structure from multiple copies of a single protein. The number of proteins required to form a spherical virus capsid is denoted by the "T-number" whereby 60t proteins are necessary. In the case of the hepatitis B virus, the T-number is 4, therefore 240 proteins assemble to form the capsid. As in the helical viruses, the spherical virus capsid may be enclosed in a lipid envelope, although frequently spherical viruses are not enveloped, and the capsid proteins themselves are directly involved in attachment and entry into the host cell.

The complete virus particle is referred to as a '''virion'''. A virion is little more than a gene transporter, and components of the envelope and capsid provide the mechanism for injecting the viral genome into a host cell.