Multiple Choice
When a virus mutates, which of the following characteristics does it exhibit?
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18. Viruses, Viroids, & Prions
Introduction to Viruses
1:30 minutesProblem 3
Textbook Question
Describe the four morphological classes of viruses, then diagram and give an example of each.
Verified step by step guidance1
Begin by defining what viral morphology means: it refers to the shape and structural features of viruses, which are important for their classification and understanding how they infect host cells.
Identify and describe the four main morphological classes of viruses: 1) Helical viruses, which have a rod-shaped or filamentous structure with capsid proteins arranged in a helix around the nucleic acid; 2) Icosahedral viruses, which have a roughly spherical shape formed by 20 equilateral triangular faces creating a symmetrical capsid; 3) Complex viruses, which have more intricate structures that do not fit into the helical or icosahedral categories, often including additional features like tails or complex outer walls; 4) Enveloped viruses, which have a lipid membrane surrounding the capsid, derived from the host cell membrane and embedded with viral glycoproteins.
For each class, sketch a simple diagram illustrating the key structural features: for example, draw a spiral for helical viruses, a geometric icosahedron for icosahedral viruses, a bacteriophage-like shape for complex viruses, and a spherical shape with an outer envelope for enveloped viruses.
Provide a well-known example of each class to solidify understanding: for helical viruses, use Tobacco mosaic virus; for icosahedral viruses, use Adenovirus; for complex viruses, use Bacteriophage T4; and for enveloped viruses, use Influenza virus.
Summarize by explaining how these morphological differences relate to viral function and infection mechanisms, emphasizing the importance of morphology in virus classification and study.
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1mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Viral Morphology
Viral morphology refers to the shape and structural features of viruses, including their capsid symmetry and presence or absence of an envelope. Understanding morphology helps classify viruses and predict their modes of infection and interaction with host cells.
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Four Morphological Classes of Viruses
The four main morphological classes of viruses are helical, icosahedral, complex, and enveloped. Helical viruses have rod-shaped capsids, icosahedral viruses have symmetrical polyhedral capsids, complex viruses have intricate structures like bacteriophages, and enveloped viruses possess a lipid membrane surrounding the capsid.
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Examples and Diagrams of Virus Classes
Each viral class can be exemplified by specific viruses: Tobacco mosaic virus (helical), Adenovirus (icosahedral), T4 bacteriophage (complex), and Influenza virus (enveloped). Diagrams typically illustrate capsid shape and envelope presence, aiding visual understanding of structural differences.
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