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A virus with this "viral envelope" uses it—along with specific receptors—to enter a new host cell. Viruses vary in shape from the simple helical and icosahedral to more complex structures. Viruses range in size from 20 to 300 nanometres; it would take 33,000 to 500,000 of them, side by side, to stretch to 1 centimetre (0.4 in).
Gamma phage, an example of virus particles (visualised by electron microscopy) Virology is the scientific study of biological viruses.It is a subfield of microbiology that focuses on their detection, structure, classification and evolution, their methods of infection and exploitation of host cells for reproduction, their interaction with host organism physiology and immunity, the diseases they ...
The genetic material of a virus is stored within a viral protein structure called the capsid. The capsid is a "shield" that protects the viral nucleic acids from getting degraded by host enzymes or other types of pesticides or pestilences. It also functions to attach the virion to its host, and enable the virion to penetrate the host cell membrane.
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. [1] Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. [2] [3] Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity.
In the past nucleic acid tests have mainly been used as a secondary test to confirm positive serological results. [3] However, as they become cheaper and more automated, they are increasingly becoming the primary tool for diagnostics and can also be use for monitoring of treatment of viral infected individuals t.
Virus classification is the process of naming viruses and placing them into a taxonomic system similar to the classification systems used for cellular organisms. Viruses are classified by phenotypic characteristics, such as morphology, nucleic acid type, mode of replication, host organisms, and the type of disease they cause.
A past paper is an examination paper from a previous year or previous years, usually used either for exam practice or for tests such as University of Oxford, [1] [2] University of Cambridge [3] College Collections. Exam candidates find past papers valuable in test preparation.
While the terms "virus" and "virion" are occasionally confused, recently "virion" is used solely to describe the virus structure outside of cells, [3] while the terms "virus/viral" are broader and also include biological properties such as the infectivity of a virion. [4]