Explain viruses and their classification, Biology

Assignment Help:

Explain Viruses and their classification?

Viruses are living organisms. Viruses are not living organisms.

No, the above is not a misprint! In fact, viruses defy the normal classification schemes that are applied to living things. First of all, they clearly lack the cellular organization that all living organisms possess. Viruses do not possess the metabolic machinery that would enable them to make proteins or to carry out metabolic processes such as respiration and photosynthesis, convert energy, acquire food, build structures, and reproduce. So right off the bat, viruses do not conform to the defining features that characterize life.

Viruses are considered to be the simplest living organisms. In fact, there are those who would not classify them among the living because they lack the organization of a "true" cell, and must rely upon true cells to reproduce. They basically consist of nucleic acids wrapped in a protein coat.

While viruses do not conform to the traditional definition of life - that is, they are not cells, and they do not reproduce by themselves - they do represent the most fundamental mechanisms of living systems. Some think of viruses as the extreme end of the evolutionary process, where they have evolved to the point of not needing the metabolic machinery that sustains the functions of cellular life. In other words, if viruses can get other cells to perform the processes of reproduction, energy trapping and conversion, then there is no need to build and maintain these organelles themselves!

Other scientists think that viruses are left over from the very first life forms to evolve, the prototypes of cells. Yet other scientists are fragments, or parts of genetic material that broke off from living cells.

Viruses are therefore difficult to classify. They do not fall under any of the traditional groupings of organisms, and so some have suggested that they represent their own kingdom. But because the viruses do not have a common ancestry, they do not lend themselves to such a grouping. About the only traits that viruses have in common are their tiny size, their simple structure, and their parasitic life style.

Viruses are very small - measuring on average between 20 and 300 nanometers across, which is about the size of the smallest bacteria. Also unlike cells, viruses are particles that can be crystalized. Some scientists refer to these particles as "active particles" because they interact with living cells. There are different types of viruses. Some contain DNA (single or double stranded), others RNA (single or double stranded). The RNA and DNA come as either linear or circular molecules, containing anywhere from 4 to a few hundred genes.

The "head" of a virus is made of a protein container called a capsid. The capsid comes in a variety of shapes and sizes - helical, polyhedral, cuboidal, or rectangular. The capsid itself is composed of building block protein subunits called capsomeres. Some types of viruses have an envelope that surrounds the capsid, which is similar to a cellular membrane. The capsid encloses the viral particle, sometimes referred to as the virion, and in some cases, also an enzyme.

LYTIC VIRUSES

Click on the Multimedia button on the left to view the life cycle of a lytic virus.


Related Discussions:- Explain viruses and their classification

Explain about the family and social history - assessment, Explain about the...

Explain about the Family and Social History - Assessment  Recent studies suggest that genetic variation plays an important role in etiology of learning problems. Hence, the col

Mechanical prosthetic valves, Mechanical Prosthetic Valves :  These patien...

Mechanical Prosthetic Valves :  These patients should have lifelong anticoagulation. In the absence of anticoagulation systemic embolism and strokes have been reported to be 5-50

Enlist the modalities available for hand wash, Q. Enlist the modalities ava...

Q. Enlist the modalities available for hand wash? Modalities available for hand wishing are a) 2-4% Chlorhexidine b) 0.3-1 %Triclosan c) 0.6% Parachlorometaxylenol (PC

Differentiate individual atoms true or false, What is the first step normal...

What is the first step normally taken when you look through the oculars? The nuclei of the cheek cells have been stained using a special dye so that they appear purple. What is the

Failure of public production, Normal 0 false false false ...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Factors affects oxygen dissociation curve - Carbon dioxide , Factors affect...

Factors affects oxygen dissociation curve - Carbon dioxide Carbon dioxide lowers the oxygen affinity of haemoglobin even if the pH is kept constant. This effect is due to the

Illustrate target organs of the hormones, Q. What are target organs of the ...

Q. What are target organs of the hormones? Target tissues, Target organs and target cells are those specific organs, cells and tissues upon which each hormone produces and acts

Assessment of ventricular septal defect, Assessment   On assessment a c...

Assessment   On assessment a child with ventricular septal defect will show clinical manifestations depending upon the size of  the defect. The small defects are usually asympt

Explain adsorption - colloidal particle, Adsorption - Colloidal particle ...

Adsorption - Colloidal particle Colloidal particles attract and hold to their surfaces the molecules of various gases, vapors and other matter with which they come into contact

Can you explain about ventriculography, Q. Can you explain about Ventriculo...

Q. Can you explain about Ventriculography? Cardiac ventriculography is a diagnostic test, i.e., used to define the anatomy and function of the ventricles (left and right) and r

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd