Virus Structure: Naked and Enveloped Viruses

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Questions and Answers

What is the primary function of the viral envelope in enveloped viruses?

To facilitate the degradation of the viral genome

To protect the virus from the host's immune system

To provide structural support to the virus

To interact with the host cell membrane during entry (correct)

Which of the following is a component of the viral capsid in naked viruses?

Viral glycoproteins

Viral envelope

Viral enzymes (correct)

Host-derived lipid bilayer

What is a characteristic of the viral genome in unenveloped viruses?

It is highly diverse in structure

It is always segmented

It is always double-stranded

It is often circular (correct)

Which of the following viral families has a circular genome?

Papovaviridae Signup and view all the answers

What is the primary difference between the structure of enveloped and unenveloped viruses?

The presence or absence of a viral envelope Signup and view all the answers

Which of the following viruses has a helical capsid and is enveloped?

Rhabdoviridae Signup and view all the answers

What is the purpose of the spikes formed by viral glycoproteins on the surface of enveloped viruses?

To interact with the host cell membrane during entry Signup and view all the answers

What is the typical size range of viruses, as measured by electron microscopy?

18-230 nm Signup and view all the answers

Why are enveloped viruses more fragile than unenveloped viruses?

Because their envelope is susceptible to environmental stresses Signup and view all the answers

What is the primary characteristic that distinguishes enveloped viruses from non-enveloped viruses?

Presence of a lipid bilayer membrane Signup and view all the answers

What is the term for the obligate intracellular parasite that lacks organelles and requires a host cell to replicate?

Virus Signup and view all the answers

Which of the following is a characteristic of unenveloped viruses?

Environmentally stable Signup and view all the answers

Match the following units

1mm = 10^(-3) cm 1 um = 10^(-6) cm 1nm = 10^(-9)cm 10nm = 10^(-8) cm Signup and view all the answers

Most viruses with DNA genome is double stranded

True Signup and view all the answers

Icosahedral capsids must be composed of penton capsomers and hexon capsomers.

False Signup and view all the answers

Penton capsomers have 5 individual proteins

True Signup and view all the answers

Which of the following is not a function of virus capsid proteins?

Replicate viral genome Signup and view all the answers

Viral Matrix protein are structural proteins of the virus found in enveloped viruses.

False Signup and view all the answers

Match the properties of RNA viruses with the correct reasoning

Some can reassort or swap genes = because they are segmented variable = replicated using RNA polymerase which is error prone as it had no proof reading mechanism adapt easily to new environments = can evolve rapidly if needed often zoonotic = variable and new genes can be introduced Signup and view all the answers

Study Notes

Virus Structure

A virus is an obligate intracellular parasite that needs a host cell to replicate, lacks organelles, and is extremely small (filterable agents) ranging from 18-230 nm in size.

Genome Composition

Viral genomes can be composed of DNA or RNA, and may be single-stranded (ss) or double-stranded (ds).
Some DNA viruses have circular genomes (e.g., Poxviridae, Asfarviridae, Herpesviridae, Papillomaviridae, Adenoviridae, Papovaviridae).
Some ds and ss RNA viruses have segmented genomes, which reduces the chances of degradation.
Parvoviridae and Circoviridae have circular genomes that are mostly double-stranded.

Capsid Structure

Naked viruses have an icosahedral capsid (e.g., Adenovirus).
Enveloped viruses have a helical capsid (e.g., Measles virus) or a complex capsid (e.g., Poxvirus).

Properties of Enveloped and Non-Enveloped Viruses

Enveloped viruses are more pleomorphic (irregularly shaped) and have a viral envelope containing host-derived lipid bilayer and embedded viral glycoproteins.
Enveloped viruses acquire their envelope by budding through the host cell membrane (except for Poxvirus, which exits by direct fusion).
Enveloped viruses are more fragile and easily destroyed by detergents, disinfectants, and outside environmental factors.
Unenveloped viruses are released by lysis of the infected cell and are more environmentally stable.

Biological Properties of Enveloped Viruses

Enveloped viruses are more easily destroyed by heat, drying, and pH changes.
Destruction of the envelope destroys the receptors needed for entry, making the virus non-infectious.
Enveloped viruses are less likely to survive in the gastrointestinal tract.

Biological Properties of Unenveloped Viruses

Unenveloped viruses are environmentally stable and can survive adverse conditions in the gut.
They can dry out and retain infectivity, making them more easily spread.
Unenveloped viruses are more resistant to detergents.

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Description

Test your knowledge on the structure of viruses, including naked and enveloped viruses, viral nucleic acid, capsid, viral enzymes, and lipid bilayer. Learn about the key components of viruses and how they interact with each other. This quiz covers the basics of virus structure and its importance in virology.