Chemistry of Life » Viruses


A virus may be defined as a microorganism that is smaller and less complex than an archae or a bacteria, which cannot grow or reproduce apart from a living cell. A virus invades living cells and uses their chemical machinery to keep itself alive and to replicate itself. Viruses can constantly mutate (change their genetic code).

This property to mutate is responsible for the ability of some viruses to change slightly in each infected person, making treatment more difficult.

The virus particle is essentially a nucleic acid which carries the genetic programme wrapped round by a protein coat. Viruses are extremely small – approximately 15-25 nanometres in diameter. The genetic material may be double-stranded DNA, double-stranded RNA, single-stranded DNA or single-stranded RNA. The viral genome can consist of a very small number of genes or up to hundreds of genes depending on the type of virus. The genome is typically organized as a long molecule that is usually straight or circular. Examples of DNA viruses are Herpes simplex virus and the Hepatitis- B virus.

The really interesting fact is that some viruses use RNA instead of DNA as their genetic material. RNA viruses have an enzyme called reverse transcriptase that permits the usual sequence of DNA-to-RNA to be reversed so the virus can make a DNA version of itself when infecting an organism. RNA viruses include HIV and hepatitis C.

The very fact of the existence of RNA viruses gives strong support to the RNA hypothesis.


Somewhere
by
Ray Goodwin


Somewhere there are mountains
Glistening in the snow
Somewhere there are mountains
That we shall never know

Somewhere there are rivers
Flowing fast and free
Somewhere there are rivers
That we can never see

Somewhere there are oceans
And sun drenched island sands
Forests full of creatures
In vastly distant lands

Somewhere there’s a planet
Beneath an alien star
The people watch our tiny sun
And wonder where we are

One day perhaps we’ll find them
Across the void of space
Perhaps through ways as yet unknown
We’ll meet them face to face


The author of this web site Ray Goodwin holds B.Sc. Degrees from London University in Chemistry, Geology and Physiology and an M.Sc. in Biochemistry. He has spent most of his professional life teaching in Colleges of Technology. On his retirement he has entered the fields of astronomy, astrochemistry, astrobiology and space sciences. He has spent a great deal of his retirement in visiting amateur astronomy societies and in attending European Space Agency Symposia in ESTEC in the Netherlands and other scientific conferences in England and Sweden. He regularly attends the yearly European Astrofest in South Kensington London and other meetings in the UK. He has written scientific articles and given a number of lectures on diverse scientific subjects.

Readers of this web site are invited to e-mail the author ( ray@lifeinthecosmos.com) and discuss their opinions of the topics dealt with and suggest any changes which they think may be helpful.

Life in the Cosmos Website
Version 01.00 - April 20, 2015.