Module 4 homework - Intro to Microbiology Module 4 Assignment Ewa Kroupa 1 Describe the different morphological types of viruses and give examples

Module 4 homework - Intro to Microbiology Module 4...

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Intro to Microbiology Module 4 Assignment Ewa Kroupa 04/30/20 1.Describe the different morphological types of viruses and give examples of each type: a.Helical: Helical capsids have rod-shaped capsomeres, connected along their long axis, resembling a wide ribbon stacked around a central axis forming a helical structure with a central cavity, a hollow tube. As a result, these virions are rod shaped or filamentous and can be short and highly rigid, as in many plant viruses, or long and very flexible, as in many animal viruses. These viruses can be naked (e.g., tobacco mosaic virus) or enveloped (e.g., influenza virus)b.Icosahedral: Three-dimensional, geometric figure with 12 corners, 20 triangular faces, and 30 edges. Arrangement of capsomeres varies between the viruses. During the assembling of an icosahedral virus the nucleic acid is packed into the center, forming a nucleocapsid. Icosahedral viruses can be naked, such as the adenovirus, or enveloped, such as the herpes simplex virus. Examples include Herpesviridae, Adenoviridae, Papovaviridae and Parvoviridae.c.Enveloped: With eneveloped viruses a viral envelope surrounds the nucleocapsid. The creation of the viral envelope through the budding process allows the viral particles to leave the host cell without disrupting the plasma membrane and therefore without killing the cell. As a result, some budding viruses can set up persistent infections. With this type of virus, some or all host membrane proteins are replaced by viral proteins. The influenza virus is an example of this kind of virus.d.Complex: Complex viruses are a special group of viruses that consist of a capsid that is neither purely helical nor completely icosahedral and has extra structures such as protein tails or a complex outer wall. The poxviruses are large, complex DNA viruses with an unusual morphology. An even more complex group of viruses are bacteriophages, viruses that infect bacteria. In general, a bacteriophage has an icosahedral head bound to a polyhedral tail, which is attached to a base plate with many protruding protein tail fibers.Poxviruses are the largest viruses, about 200 nm in diameter and 300 nm in length, with very complex nucleocapsid symmetry. They vary in shape depending on the species, but for the most part they are brick shaped or in oval form, similar to a rounded brick.

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