Viruses, Biology

Viruses

Viruses are sub cellular, ultramicroscopic infectious agents of 20 nm-300 nm size range Many of them cause diseases like polio, dengue, small pox, measles, rabies, common cold etc., in animals and mosaic, dwarfing, curling etc. in plants. They are obligate intracellular parasites. In other words, they multiply only inside living cells. They consist of a protein coat or capsid surrounding a nucleic acid core of either DNA or RNA.Viruses were discovered in 1892 by a Russian biologist Iwanowsky, as'filter-passing agents' though they were seen much later, with the advent of electron microscope.

They share certain characteristics of both living and non-living things. So it will be useful to examine the properties of viruses. They are considered living because they can reproduce even though only when they are inside host cells, using the host cell machinery. On the other hand, they have some nonliving properties as well. When they are outside the host cell they can also undergo crystallisation like any other chemical substance. They do not have metabolism and so are metabolically inert. They cannot take up metabolic substances from the environment and lack the biochemical machinery like ribosomes or ATP generating systems to synthesize nucleic acid and proteins. They do not have their own enzyme system. They also do not exhibit growth or respond to stimuli.

Posted Date: 1/12/2013 2:38:11 AM | Location : United States







Related Discussions:- Viruses, Assignment Help, Ask Question on Viruses, Get Answer, Expert's Help, Viruses Discussions

Write discussion on Viruses
Your posts are moderated
Related Questions
What do ATP and ADP mean? What are the roles of these molecules for the cellular energetic metabolism? ATP is an abbreviation of adenosine triphosphate, a molecule made of aden

Explain the Small Intestine? The small intestine is made up of three sections, the duodenum, the jejunum, and the ileum. Bile from the liver and pancreatic enzymes are released

Explain Ventilation, Chest Compressions? Even when the first three defibrillation attempts fail, the best chance of resuscitation still lies in successful defibrillation. Hence

Substrates are reagent molecules upon which enzymes act. The enzyme has spatial binding sites for the attachment of its substrate. These sites are known as activation centers of

The citric acid cycle, also called as the tricarboxylic acid (TCA) cycle or Krebs cycle (after its discoverer in the year of 1937), is used to oxidize the pyruvate making during th

Explain the hormonal control of the reproductive system in human male. Define totipotency. Verify the two different routes of regenerating plantlets from callus culture.

Q. Explain about Modifiable Risk Factors? 1. Behavioural Smoking Sedentary Lifestyle Habits Dietary Errors 2. Physiological Hyperlipidemia Hypertension Obe

Explain about the Component of Metalloenzymes? Zinc is unique among the trace elements in that it is a part of enzymes for all six Enzyme Commission classes. As a component of

Explain the effect on Minerals of the Human milk? There appears to be no relationship between dietary intake and concentrations in milk for copper, iron or zinc. Iron supplemen

What are some things that have algae in them? Yeast is considered Algae.