Podcast
Questions and Answers
Which of the following mechanisms explains how some enveloped viruses release new virions without necessarily killing the host cell?
Which of the following mechanisms explains how some enveloped viruses release new virions without necessarily killing the host cell?
- Exocytosis via lysosomes, which degrades the host cell from within.
- Direct membrane lysis, causing immediate cell death and virion release.
- Integration of viral DNA into the host genome, leading to persistent infection without virion release.
- Budding, where the virus acquires part of the host's membrane as its envelope. (correct)
A researcher is studying a newly discovered virus that infects eukaryotic cells. Initial observations show that the virus's genome must be transported into the host cell nucleus for replication. Based on this information, which of the following is the most likely classification of this virus?
A researcher is studying a newly discovered virus that infects eukaryotic cells. Initial observations show that the virus's genome must be transported into the host cell nucleus for replication. Based on this information, which of the following is the most likely classification of this virus?
- A negative-sense single-stranded RNA virus.
- A double-stranded DNA virus. (correct)
- A positive-sense single-stranded RNA virus.
- A retrovirus that uses reverse transcriptase.
A non-enveloped virus relies on which mechanism to facilitate its entry into a host cell?
A non-enveloped virus relies on which mechanism to facilitate its entry into a host cell?
- Endocytosis, followed by release of the viral nucleic acid from the endocytic vesicle. (correct)
- Fusion of the viral envelope with the host cell membrane.
- Direct injection of viral genome through a pore formed in the host membrane.
- Attachment to the host cell receptors, causing immediate lysis of the cell.
A key difference between early and late viral proteins, especially in RNA viruses, lies in their function and timing of synthesis. Which statement accurately describes this difference?
A key difference between early and late viral proteins, especially in RNA viruses, lies in their function and timing of synthesis. Which statement accurately describes this difference?
Which of the following mechanisms is most commonly associated with the release of non-enveloped viruses from a host cell?
Which of the following mechanisms is most commonly associated with the release of non-enveloped viruses from a host cell?
What is the primary reason DNA viruses must enter the host cell nucleus to replicate?
What is the primary reason DNA viruses must enter the host cell nucleus to replicate?
How does the viral mRNA of DNA viruses differ in its processing compared to the viral RNA of RNA viruses within an infected host cell?
How does the viral mRNA of DNA viruses differ in its processing compared to the viral RNA of RNA viruses within an infected host cell?
What is the role of viral attachment proteins, or spikes, in the initial stages of viral infection?
What is the role of viral attachment proteins, or spikes, in the initial stages of viral infection?
During viral entry via endocytosis, what critical step must occur after the virion is engulfed by the host cell membrane?
During viral entry via endocytosis, what critical step must occur after the virion is engulfed by the host cell membrane?
If a virus uses the host cell's endoplasmic reticulum (ER) and Golgi apparatus for pH-dependent maturation and subsequent release, which mechanism is it most likely employing?
If a virus uses the host cell's endoplasmic reticulum (ER) and Golgi apparatus for pH-dependent maturation and subsequent release, which mechanism is it most likely employing?
Flashcards
Viral Attachment
Viral Attachment
The initial step where a virus attaches to a host cell using viral proteins that bind to receptors on the cell surface.
Penetration and Uncoating
Penetration and Uncoating
The process by which a virus enters the host cell, either by fusion or endocytosis, followed by the release of the viral genome.
Replication and Protein Synthesis
Replication and Protein Synthesis
The stage where the virus uses the host cell's machinery to produce viral genetic material and proteins.
Viral Assembly
Viral Assembly
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Viral Release
Viral Release
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Enveloped Viruses
Enveloped Viruses
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Non-Enveloped Viruses
Non-Enveloped Viruses
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RNA Viruses
RNA Viruses
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DNA Viruses
DNA Viruses
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Early Viral Proteins
Early Viral Proteins
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Study Notes
- The purpose of the video is to explain the infectivity of DNA and RNA viruses, and discuss the differences between them in replication, interaction with host cells, and entry/release mechanisms.
Virus Infection Process
- The initial step in virus infection involves viral attachment proteins or structures on the virion surface binding to host cell receptors
- Receptors can be proteins, carbohydrates, glycoproteins, or glycolipids
- Penetration and uncoating of viruses differ between enveloped and non-enveloped viruses
- Enveloped viruses enter host cells through fusion or endocytosis, while non-enveloped viruses enter through endocytosis
Enveloped Virus Entry Mechanisms
- Virions attach to host cell receptors via surface spikes
- The viral envelope fuses with the host cell's plasma membrane, releasing the nucleocapsid into the cytoplasm
- Nucleic acid separates from the protein coat (uncoating)
- The virus absorbs to the host cell via surface proteins, and the virion is taken in by endocytosis
- The host cell plasma membrane surrounds the virion, forming a vesicle
- The viral envelope fuses with the vesicle's plasma membrane, releasing the nucleocapsid into the host cytoplasm
Non-Enveloped Virus Entry Mechanisms
- Naked virions enter by endocytosis
- Since there is no envelope, it cannot fuse with the plasma membrane
- After being engulfed, the virion's nucleic acid is released from the endocytic vesicle
Replication and Protein Synthesis
- Viruses replicate genetic material and synthesize structural proteins within the host cell
- Self-assembly and release of new virus particles occur
- Viral RNA is transformed into mRNA, initiating viral protein translation
- Viral mRNA encodes several proteins
- Early proteins are involved in replication processes, produced in smaller amounts
- Structural or late proteins are produced subsequently and in larger quantities
Release of New Virions
- New virions are released via three pathways
- Particles travel through the endoplasmic reticulum (ER) and Golgi apparatus for exocytosis inside cell compartments, where they undergo pH-dependent maturation
- Viruses are released by budding, where viral proteins integrate into the host membrane, which the virion acquires as its envelope (ER, Golgi, or plasma membrane)
- Budding facilitates assembly of viral components directly at the budding site
- Non-enveloped viruses are commonly released through cell lysis, disrupting the plasma membrane and killing the host cell
DNA Viruses
- Genome of DNA viruses must be delivered into the host nucleus
- Nuclear import accompanies or follows virion uncoating
- Some viral DNA might need transformation into positive-sense, double-stranded DNA for transcription
- Transcription produces mRNA, which is treated like regular host mRNA and travels to the cytoplasm for translation
- DNA replication occurs in the cell's nucleus, using mostly cellular proteins to assemble new viral particles
- Structural viral proteins are transported into the nucleus, where they self-assemble into virions
- Virions penetrate the nuclear membrane via vesicle formation and are subsequently released from the cell
Key Differences in Virus Types
- RNA viruses convert RNA to mRNA for protein production
- RNA viruses exit through budding (if enveloped) or cell lysis (if non-enveloped)
- Early proteins are involved in replication, while late proteins form the virus structure
- DNA viruses must enter the host nucleus for replication and transcription employing the cell’s machinery to replicate and assemble new viral particles
- DNA viruses make mRNA like host cells do
- Virions are assembled in the nucleus and released via vesicle formation
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