Anatomy of the Virus

A virus consists of a genome enclosed in a protein coat called a capsid. This capsid protects the genome from the environment while it is outside of the host cell.

This image shows the DNA of the adenovirus inside of the capsid. Some capsids have icosahedral geometry as shown in this figure:

The capsid also aids the virus in attaching entering a host. The surface proteins, such as the ones labeled "fiber" in the first image attach to proteins on cells. Some viruses have an envelope, a lipid membrane that surrounds the capsid. There is a variety of shapes and sizes, they can be icosahedral, helical, or alien robotish like bacteriophages.

A single infectious particle is called a virion.

Viruses also show diversity in genetic make up. Excluding a lot of viruses, all life starts with the blue prints of double stranded DNA. From bacteria and protozoa to trees and tigers. But viruses can use either DNA or RNA. Further, it can be either single stranded (ss) or double stranded (ds), or linear or circular (bacterial DNA is circular and eukaryotic is linear). Bacteriophage phiX 174 is a ds DNA virus. The Papillomaviruses have circular ds DNA.

Viruses are relatively simple organisms, and carry none or  a few proteins and enzymes with them. This creates a problem, since they have no enzymes to carry out tasks such as building nucleic acid (essential for replication) for DNA or RNA, nor can they create usable energy. They have no ribosomes to synthesize proteins. To overcome this problem they essentially hijack other living organisms and use their machinery to make new viruses. Because of this viruses are considered obligatory intracellular parasites.

Stay tuned for scenes from the next entry!!

So next time I'll cover influenza and vaccines. After that I want to do ebola, HIV, MRSA, papillomavirus, herpes, neisseria, and an enterobacteriaceae. If you want to see anything in particular just ask!

Also some feedback would be really appreciated, was it easy to follow, confusing, boring, etc.