Chapter 13, Problem 1TMW

Why are naked icosahedral viruses able to crystallize?

Summary Introduction

To tell:

Why naked icosahedral viruses are able to crystallize.

Introduction:

The viruses are obligate parasitic organisms that show signs of life only inside a host. Outside the host, they either die or do not show any sign of life. They invade the host cell to carry out their function like replication. Depending upon the state of the virus, they can carry out lytic cycle or lysogenic cycle.

Explanation of Solution

The viruses are very unique organisms that act as a non-living organism outside the host cell and living organism inside the host cell. The viruses have a membranous protein coat called as an envelope. Some viruses lack these envelopes and are known to be naked viruses. The majority of the viruses have icosahedral capsid, and some viruses have helical capsids; most of non-enveloped viruses have icosahedral capsids. The capsid is a protein coat that protects the genetic material of the viruses. The protein sub-units of the capsids are called capsomeres. The nucleocapsid is a joint term of the nucleic acid of the virus and its capsid; these are able to crystalize under chemicals. When compared with enveloped icosahedral viruses, the naked icosahedral viruses are easily crystalized under the influence of some chemicals. The crystallization occurs due to the absence of glycoproteins and phospholipids as seen in enveloped viruses.

Conclusion

The crystallization is very useful in viewing of viruses under electron microscope.