Virus Basics and Structure

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which of the following components is always present in all viruses?

Envelope

Capsid (correct)

Metabolic machinery

Ribosomes

What distinguishes viruses from living cells?

Ability to generate energy

No cytoplasmic membrane (correct)

Presence of ribosomes

Ability to replicate independently

What type of nucleic acid can viruses have?

Only DNA

Either RNA or DNA, but not both (correct)

Both RNA and DNA

Only RNA

How do viruses primarily reproduce?

By hijacking a host's cellular machinery Signup and view all the answers

Which statement accurately describes the ‘life’ of a virus?

Viruses cannot grow in size. Signup and view all the answers

What are capsomeres?

Subunits that form the capsid Signup and view all the answers

What is a characteristic of viral genomes?

They are usually smaller than bacterial genomes. Signup and view all the answers

What kind of host range do most viruses have?

Narrow host range Signup and view all the answers

What type of virus is SARS-COV-2 classified as?

Enveloped virus Signup and view all the answers

Which component is responsible for the self-assembly of the capsid in icosahedral viruses?

Capsid proteins Signup and view all the answers

During which stage does a bacteriophage inject its genetic material into the host cell?

Penetration Signup and view all the answers

Which of the following viruses is an example of a complex virus?

Smallpox virus Signup and view all the answers

What mechanism do filamentous viruses like M13 utilize to enter a bacterial cell?

Hijacking the pilus retraction Signup and view all the answers

What is the first step in the viral replication cycle of a lytic bacteriophage?

Attachment Signup and view all the answers

How do phages, such as T4, typically attach to host cells?

Using specific molecules on the host surface Signup and view all the answers

Which virus is characterized by having a filamentous structure?

Tobacco mosaic virus Signup and view all the answers

What process occurs first in the synthesis stage of viral replication for a dsDNA virus?

Transcription of viral genes to make viral mRNA Signup and view all the answers

Which statement is true regarding ssRNA (+) viruses?

They can be expressed directly as viral mRNA. Signup and view all the answers

What is required for the synthesis of proteins in dsDNA viruses?

Transcription of viral mRNA Signup and view all the answers

Which of the following must be true for an ssDNA (+) virus?

The virus typically has an origin of replication. Signup and view all the answers

What is essential for the replication of ssRNA (-) viruses?

RNA dependent RNA polymerase Signup and view all the answers

How does the host's RNA polymerase interact with a dsDNA virus?

It makes a complementary copy of the viral mRNA. Signup and view all the answers

Which enzyme is required by RNA viruses that replicate their RNA genomes?

RNA dependent RNA polymerase Signup and view all the answers

What is a common feature among ssRNA (-) viruses?

They require the synthesis of a complementary strand first. Signup and view all the answers

Study Notes

Virus Basics

Viruses are not cells
Lack cytoplasmic membrane, cytoplasm, and ribosomes
Significantly smaller than cells
Obligate intracellular parasites—must reproduce inside a host cell
Exhibit a diverse range of genome types (DNA or RNA, single-stranded or double-stranded, linear or circular)
Display varied shapes (spherical, helical, polyhedral, complex)
Demonstrate a discrete host range, typically with narrow specificity

Viral Structure

All viruses contain a nucleic acid genome (DNA or RNA, never both)
Enveloped viruses possess an outer lipid layer (not a cell membrane, derived from the host cell)
Some viruses feature a capsid—a protective protein coat—with polyhedral or helical symmetry.
Capsids are composed of capsomeres, structural subunits, essential for self-assembly.
Additional components include enzymes within certain viruses.

Viral Replication

Replication cycle of a lytic bacteriophage, including attachment, penetration (of host cells, including bacteria), synthesis (of viral components, from host resources), assembly (of complete virus particles), and release (from host cells, that destroy the host cell) from the host.
This process can lead to cell lysis (breaking open of the host cell due to virus production).
Viral attachment is specific, involving interactions with host cell surface molecules.
Penetration mechanisms vary among virus types and include factors such as exploiting host cell surface structures (like pili) for entry.

Viral Genomes

dsDNA viruses: characterized by the transcription of DNA into mRNA and further translation into viral proteins, and DNA replication (uses host cell resources).
(+)ssRNA viruses: immediately translated into viral proteins and mRNA is made directly from the ssRNA (+).
(-)ssRNA viruses use RNA-dependent RNA polymerase (i.e. use mRNA for protein creation).
(+)ssDNA viruses: require transcription into mRNA for translation to create viral proteins, then DNA replication occurs.

Other Key Facts

Viruses can evolve and adapt to their host environments.
Viruses are diverse in their structures and genomes, reflecting their evolutionary history.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the fundamental principles of viruses, including their basic structure, characteristics, and replication methods. Understand the differences between various types of viral genomes and the unique aspects of viral infection. This quiz will enhance your knowledge of virology and the role viruses play in the biological world.