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Are Viruses Alive?

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Introduction

´╗┐Are Viruses Alive? What is a Virus? Viruses are very small microorganisms, much smaller than bacteria. They are among the smallest organisms known and consist of a fragment of genetic material inside a protective protein coat. Viruses can only reproduce inside host cells and as a result, they damage the cell when they do this. Once a virus has invaded a cell, it then takes over and makes copies of itself. Eventually the copies of the virus fill the whole host cell, causing it to burst open. The viruses are then passed out in the bloodstream, the airways, or by other routes. ...read more.

Middle

They are arranged in a precise and highly repetitive pattern around the nucleic acid. A single type of capsomere or several chemically distinct types may make up the capsid. 3. Some viruses contain an envelope. An envelope is a membrane-like structure that encloses the nucleocapsid and is obtained from a host cell during the replication process. The envelope contains viral-specified proteins that make it unique. The envelope of certain viruses is a lipid bilayer containing glycoproteins set in the lipid. The envelope causes the virus to appear. Projections from the envelope are known as spikes. The spikes can sometimes contain essential elements that allow the virus to attach to the host cell. ...read more.

Conclusion

Reproduction ? Making more organisms in one of two ways, asexual or sexual reproduction 6. Excretion ? Getting rid of waste products 7. Nutrition ? Taking in and using food So are Viruses Alive? To be accepted as alive, an organism must be able to perform all seven of the life processes. Viruses qualify under all of these categories except respiration and reproduction, for which they act as a parasite and require a host cell to do it for them. Without the host cell, a virus would only be a piece of a genetic molecule and not be able to do anything by itself; therefore it cannot be a living thing. Sources 1. BBC Bitesize 2. http://www.scientificamerican.com/article.cfm?id=are-viruses-alive-2004 3. Textbooks and exercise books e.g. CGP guides and GCSE exercise book 4. http://www.johnkyrk.com/virus.html ALL IMAGES ARE FROM GOOGLE IMAGES ...read more.

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