Viruses as non-living killers

Welcome to Advanced Biology blog! 

 

My name is Anel Turgambayeva. I am a first year undergraduate student with Biology major and a host of this page.  I have taken a class in Modern Biology I. Since I have been really interested in the area of Microbiology, I decided to create a blog that is aimed to introduce you with the fascinating world of microbes and give the detailed information about these microscopic creatures. 

 

What Virology is about?

According to the College dictionary, virology– is a biological science that concerned with the study of the smallest microorganisms – viruses. This discipline is focused on the exploration of the nature, structure, chemical composition, relationship with the organism and the environment, ecology, prevention and treatment of viral diseases. 

Are viruses alive?

Viruses are the most mysterious creatures among microorganisms. Viruses differ significantly from other types of microorganisms. They are acellular life forms and incapable of self-reproduction and metabolism. For this reason viruses follow the parasitic way of life: they use the internal machinery of the host cell to replicate, grow and produce their own proteins. As viruses do not perform the functions of the living things, they are considered to be non-living structures.

Structure of viruses

 

As it was mentioned before, viruses do not have a cellular structure. Each virus is arranged in a very simple way - it consists of genetic information carrier that located in the centre of virus, and the shell.

Genetic material is a short nucleic acid molecule which forms the core of the virus. The nucleic acid of viruses can be represented as DNA or RNA. Shell that encodes that genetic core of virus called capsid. It consists of subunits - capsomeres, each of which constituted from one or two protein molecules. The structure of the virus is illustrated in figure1. 

figure 1. Structure of virus

Shapes and symmetry of viruses

 The capsomers of each virus arranged in a certain type of symmetry. If capsid acquires tubular as tobacco mosaic virus form this type of symmetry is called helical (figure 2, at the right). In isometric symmetry viral capsid have more spherical shape (figure2, in the middle). In the case of complex symmetry capsid has a cubic shape and located within the nucleic acid that stacked spirally (figure 3). Correct geometry of the capsid even allows viral particles together to form a crystalline structure.

 

figure 2. Viral symmetry. Helical (right) and Isometric (middle)

 

figure 3. Complex viruses

Viruses are diverse in sizes. They are roughly 17nm – 1000nm in diameter, which is approximately 50-fold less size of bacteria. They cannot be seen under the light microscope, as their length is less than the wavelength of light. Thus to observe the structure of viruses the electronic microscope is applicable. 

Viral diseases

 

Despite of the simplicity of the structure, viruses are capable to cause different diseases virtually in all organisms, including bacteria, plants and animals. There is a great number of viral diseases among people, The most common of them are influenza, smallpox, polio and etc. and I would like to describe in details one of the most dangerous human viral diseases known as AIDS.

AIDS 

AIDS - one of the most important and tragic problems encountered by the world at the end of the 20th century. The agents that cause AIDS are known as Human Immunodeficiency Virus (HIV). HIV is known as a killer virus. The uniqueness of these pathogens is in the way they enter and infect a cell: the coat of HIV fuses with the plasma membrane of a host cell and virus releases its genetic material (RNA) and other chemicals into the cell.  Further, HIV starts to reproduce and manufacture necessary for growth and development things in the host cell. The target cells of that agents are "helper" T-4 lymphocytes, cells that destroy infectious agents and disease. As the number of T-4 lymphocytes falls the effectiveness of the immune system is lowered significantly. Thus, even the minor infections  can lead to serious consequences in patients with AIDS.

The treatment of AIDS does not exist yet, but there are a lot of drugs that slow down the destruction of the immune system and are thus able to significantly prolong the lives of HIV-infected patients. 

  Reference list

"BIO-DIVERSITY - PART I." Boddunan. 

https://www.boddunan.com/articles/science-nature/71-wild-life/8521-bio-diversity-part-i.html (accessed September 26, 2014).

Raven, Peter H., and George B.Johnson. 2001. “Viruses”. Biology.

http://www.mhhe.com/biosci/genbio/raven6b/graphics/raven06b/other/raven06_33.pdf (accessed September 25, 2014).

 "Virology dictionary definition". Browse Webster's New World College Dictionar. 1996.  http://www.yourdictionary.com/virology (accessed September 25, 2014).

"Capsomer definition." Mondofacto. 2009.

http://www.mondofacto.com/facts/dictionary?query=capsomer(accessed September 26, 2014).  

"T4 helper lymphocyte".  Mondofacto. 2009.

http://www.mondofacto.com/facts/dictionary?t4+helper+lymphocyte(accessed September 25, 2014).  

Mahy J. and Pattison R. 1984. Structure of viruses.Pages: 33-36. Published by Cambridge University Press. http://crystal.harvard.edu/lib-sch/HarrisonS-84-Microbe-_-29.pdf. (accessed September 25, 2014). 

  

What Is HIV? http://www.aids.gov/hiv-aids-basics/hiv-aids-101/what-is-hiv-aids/ (accessed September 26, 2014).