Definition of Capsid



The outer shell of a virus particle is made up of proteins and it is called a capsid. Inside this capsid is present the nucleic acid i.e. DNA or RNA. The capsid is responsible for providing the specificity to the viruses. In certain viruses, this capsid is further enveloped by a fatty layer. Such virions become inactivated when they are exposed to fat solvents e.g. ether and chloroform.

 


Most of the virions are composed of a capsid that has twenty triangular faces. They are arranged in the form of capsomeres and the nucleic acid present inside them is densely coiled. The capsid of other virions consists of irregular spikes that are present on their surface. The capsid of the viruses that attack plants is a naked cylinder and lacks the fatty layer.

 

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