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Questions and Answers

What is the extracellular form of a virus that facilitates transmission?

Virion (correct)

Capsid

Enveloped virus

Nucleic acid genome

Which type of virus has no other layers apart from the protein shell that surrounds its genome?

Adenovirus

Naked virus (correct)

Enveloped virus

Retrovirus

What is the genetic element that can multiply only in a living (host) cell?

Viroid

Prion

Bacteriophage

Virus (correct)

What does a virus need a host cell for?

Energy, metabolic intermediates, protein synthesis Signup and view all the answers

What is the protein shell that surrounds the genome of a virus called?

Capsid Signup and view all the answers

Which type of virus has an additional lipid bilayer surrounding its capsid?

Enveloped virus Signup and view all the answers

What is the nucleic acid genome of a virus used for?

Carrying genetic information Signup and view all the answers

Which type of virus is an obligate intracellular parasite?

All viruses Signup and view all the answers

What is the term for the genetic element that can multiply only in a living cell?

Virus Signup and view all the answers

Which type of viruses include most bacterial and plant viruses?

Naked viruses Signup and view all the answers

Which mechanism do prokaryotes use to diminish viral infections?

Toxin-antitoxin molecules Signup and view all the answers

What is the role of the tail fibers in bacteriophage T4 infection?

To inject viral DNA into host cytoplasm Signup and view all the answers

How do temperate bacteriophages differ from virulent bacteriophages?

They can enter lysogeny Signup and view all the answers

What is a characteristic of retroviruses like HIV?

They integrate into the host genome using reverse transcription and integrase Signup and view all the answers

What is a characteristic of animal viruses during infection of host cells?

They involve specific host cell receptors, cell entry, and genome replication Signup and view all the answers

What is a characteristic of the influenza virus genome?

It is segmented Signup and view all the answers

What is the outcome of viral infection that involves the integration of viral genome into the host genome?

Transformation Signup and view all the answers

What is a characteristic of coronaviruses like SARS-CoV-2?

They cause respiratory infections and utilize genomic RNA for virion assembly Signup and view all the answers

What is the function of CRISPR in prokaryotes' defense against viral infections?

It provides acquired immunity by targeting and cleaving viral DNA Signup and view all the answers

What is the role of middle proteins in the replication of T4 bacteriophage?

They are involved in viral protein synthesis Signup and view all the answers

Which phase of the growth curve of viruses involves the synthesis of viral nucleic acid and proteins?

Latent period Signup and view all the answers

What is the primary function of outer surface proteins in enveloped viruses?

Attachment and infection Signup and view all the answers

What is the primary difference between virulent (lytic) and lysogenic infections?

Lytic infections destroy the host, while lysogenic infections alter the host cell genetically Signup and view all the answers

What is the primary role of plaque assay in virology?

Measuring the titer of infectious virions per volume of fluid Signup and view all the answers

What is the main purpose of the nucleocapsid in enveloped viruses?

Containing nucleic acid and protein Signup and view all the answers

What determines the shape of viruses?

Symmetry Signup and view all the answers

What is the primary classification basis for viruses?

Nature of genetic material and host specificity Signup and view all the answers

What is the primary function of bacteriophage receptors on the host cell surface?

Facilitating attachment and entry of the bacteriophage Signup and view all the answers

How do some viruses exert beneficial effects?

Increasing drought tolerance in plants or decreasing HIV replication and infectivity Signup and view all the answers

What is the primary role of the burst size in the replication cycle of prokaryotic viruses?

Indicating the number of virions released from the host cell Signup and view all the answers

Study Notes

Viral Structure and Activities Summary

Viruses have an outer layer consisting of a phospholipid bilayer and viral proteins, and a nucleocapsid containing nucleic acid and protein in enveloped viruses.
Virulent (lytic) infection destroys the host, redirecting host cell metabolism to support multiplication and virion assembly, while lysogenic infection alters the host cell genetically by integrating viral genome into the host genome.
Viruses can be classified based on the nature of their genetic material (DNA or RNA), single-stranded or double-stranded, and the hosts they infect (bacterial, animal, plant, etc.).
Some viruses exert beneficial effects, such as increasing drought tolerance in plants or decreasing HIV replication and infectivity.
Virion structure includes capsomeres, with some viruses having a single capsid protein due to the small size of viral genomes, and can be assembled spontaneously or with host cell folding assistance.
Viruses exhibit two primary shapes, rod and spherical, with helical and icosahedral symmetry respectively, and some viruses have complex structures like head-plus tail bacteriophages.
Enveloped viruses have a nucleocapsid surrounded by a lipoprotein membrane and use outer surface proteins for attachment and infection, while some have specific enzymes like lysozyme, neuraminidases, and nucleic acid polymerases inside virions.
Culturing and detecting bacteriophages can be done using plaque assay, which measures the titer (number of infectious virions per volume of fluid).
Animal cell culture and viral plaques are similar to plaque assay of bacteriophages, and the efficiency of infection is usually much lower than 100% due to defective virions or inappropriate conditions for infectivity.
The replication cycle of prokaryotic viruses involves attachment, penetration, synthesis of viral nucleic acid and proteins, assembly of capsids, and release of new virions from the host cell.
The growth curve of viruses includes an eclipse phase, maturation, latent period, and release, with burst size indicating the number of virions released.
Attachment and entry of bacteriophage T4 to the host cell require complementary receptors on the host cell surface, with receptors carrying out normal host functions and varying depending on the phage.

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Test your knowledge of viral structure and activities with this comprehensive quiz. Explore topics such as viral classification, infection mechanisms, virion structure, culturing and detection methods, and the replication cycle of prokaryotic viruses. Challenge yourself with questions on viral shapes, genome types, and the beneficial effects of viruses.

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