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Questions and Answers
Viruses are measured in ______, which is one-billionth of a meter.
Viruses are measured in ______, which is one-billionth of a meter.
nanometers
The ______ of a light microscope is limited to about 200nm.
The ______ of a light microscope is limited to about 200nm.
resolution
A complete virus particle is known as a ______.
A complete virus particle is known as a ______.
virion
The ______ is made from proteins encoded by the viral genome.
The ______ is made from proteins encoded by the viral genome.
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Viruses can have a lipid ______ derived from the host cell membrane.
Viruses can have a lipid ______ derived from the host cell membrane.
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The association of viral capsid proteins with viral nucleic acid is called a ______.
The association of viral capsid proteins with viral nucleic acid is called a ______.
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Viruses are classified by factors such as their core content, capsid structure, presence of outer envelope, and how ______ is produced.
Viruses are classified by factors such as their core content, capsid structure, presence of outer envelope, and how ______ is produced.
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______ have no effect on viruses.
______ have no effect on viruses.
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The size of a virus ranges from ______ nm in diameter.
The size of a virus ranges from ______ nm in diameter.
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The smallest virus, ______, has a size of 20nm.
The smallest virus, ______, has a size of 20nm.
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Most animal viruses have a ______ shape.
Most animal viruses have a ______ shape.
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Viruses are typically inactivated by heating at ______°C for 30 minutes or 100°C for a few seconds.
Viruses are typically inactivated by heating at ______°C for 30 minutes or 100°C for a few seconds.
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Both non-ionizing and ionizing radiation can ______ viruses.
Both non-ionizing and ionizing radiation can ______ viruses.
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Viral genomes contain either ______ or RNA, but not both.
Viral genomes contain either ______ or RNA, but not both.
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The ______ is the outer shell of a virus.
The ______ is the outer shell of a virus.
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Some viruses contain a phospholipid bilayer known as an ______.
Some viruses contain a phospholipid bilayer known as an ______.
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Group VI viruses are known as ssRNA-RT viruses, which have a ______ intermediate in their life-cycle.
Group VI viruses are known as ssRNA-RT viruses, which have a ______ intermediate in their life-cycle.
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Group VII viruses are classified as dsDNA-RT viruses, which means they have ______ with an RNA intermediate in their life-cycle.
Group VII viruses are classified as dsDNA-RT viruses, which means they have ______ with an RNA intermediate in their life-cycle.
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For proper infection and progeny production, viruses need the host cell to be in ______.
For proper infection and progeny production, viruses need the host cell to be in ______.
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Herpesviridae, Adenoviridae, and Papovaviridae are examples of Group ______ viruses.
Herpesviridae, Adenoviridae, and Papovaviridae are examples of Group ______ viruses.
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Parvoviridae is known to be the only exception in Group II that does not have a ______ genome.
Parvoviridae is known to be the only exception in Group II that does not have a ______ genome.
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Group III viruses are categorized as double-stranded RNA viruses and mainly include the ______ family.
Group III viruses are categorized as double-stranded RNA viruses and mainly include the ______ family.
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Positive-sense single-stranded RNA viruses, classified under Group IV, replicate through a ______ intermediate.
Positive-sense single-stranded RNA viruses, classified under Group IV, replicate through a ______ intermediate.
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The Poxvirus family is a well-studied example of a class 1 virus that does not replicate within the ______.
The Poxvirus family is a well-studied example of a class 1 virus that does not replicate within the ______.
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Viral pathogenesis studies the interaction between viral and host ______ factors.
Viral pathogenesis studies the interaction between viral and host ______ factors.
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For infection to occur, the virus must hijack the host factors and evade the host ______ response.
For infection to occur, the virus must hijack the host factors and evade the host ______ response.
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A virus is pathogenic if it can infect and cause signs of ______ in that host.
A virus is pathogenic if it can infect and cause signs of ______ in that host.
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Viruses usually replicate at the primary site of ______.
Viruses usually replicate at the primary site of ______.
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Intracellular spread occurs through fusion of infected cells with adjacent ______ cells.
Intracellular spread occurs through fusion of infected cells with adjacent ______ cells.
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The predominant mode of viral dissemination is via the ______ system.
The predominant mode of viral dissemination is via the ______ system.
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The presence of virus in the blood is called ______.
The presence of virus in the blood is called ______.
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Certain other viruses can be directly introduced into the ______ stream.
Certain other viruses can be directly introduced into the ______ stream.
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The genetic material which is single-stranded RNA (ssRNA), but ssDNA in some cases, is bound into the protein helix by interactions between the negatively charged nucleic acid and positive charges on the ______.
The genetic material which is single-stranded RNA (ssRNA), but ssDNA in some cases, is bound into the protein helix by interactions between the negatively charged nucleic acid and positive charges on the ______.
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The length of a helical capsid is related to the length of the ______ contained within it.
The length of a helical capsid is related to the length of the ______ contained within it.
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Viruses can be categorized into naked or enveloped helical based on the presence or absence of a viral ______.
Viruses can be categorized into naked or enveloped helical based on the presence or absence of a viral ______.
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The most well-studied tobacco mosaic virus is a naked ______ virus.
The most well-studied tobacco mosaic virus is a naked ______ virus.
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The icosahedron is a polygon with 12 corners and 20 facets made up of equilateral ______.
The icosahedron is a polygon with 12 corners and 20 facets made up of equilateral ______.
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Viruses with icosahedral structures are released into the environment when the cell dies, breaks down, and ______.
Viruses with icosahedral structures are released into the environment when the cell dies, breaks down, and ______.
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The head of the bacteriophage has an icosahedral shape with a ______ shaped tail.
The head of the bacteriophage has an icosahedral shape with a ______ shaped tail.
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Envelope viruses are surrounded by a lipid bilayer membrane formed when the virus is exiting the host cell via ______.
Envelope viruses are surrounded by a lipid bilayer membrane formed when the virus is exiting the host cell via ______.
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Viruses use ______ to create templates for protein synthesis.
Viruses use ______ to create templates for protein synthesis.
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Negative-sense RNA viruses must be transcribed by viral ______ into a readable form.
Negative-sense RNA viruses must be transcribed by viral ______ into a readable form.
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Replication of non-segmented genome viruses occurs in the ______.
Replication of non-segmented genome viruses occurs in the ______.
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Viruses with segmented genomes replicate in the ______.
Viruses with segmented genomes replicate in the ______.
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The Hepatitis B virus belongs to the ______ family of viruses.
The Hepatitis B virus belongs to the ______ family of viruses.
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Viruses can only reproduce within their ______ cells.
Viruses can only reproduce within their ______ cells.
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Parental virus gives rise to numerous genetically identical ______.
Parental virus gives rise to numerous genetically identical ______.
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The virus attaches to the host cell membrane through interaction of viral proteins present on the ______.
The virus attaches to the host cell membrane through interaction of viral proteins present on the ______.
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Flashcards
Size of viruses
Size of viruses
Viruses range from 20 to 300 nm in diameter. Parvovirus is the smallest, while Poxvirus is around 400 nm.
Virus shapes
Virus shapes
Viruses can have various shapes: spherical, rectangular, rod, bullet, or irregular.
Virus symmetry
Virus symmetry
Viruses may exhibit helical or icosahedral symmetry, or more complex forms.
Temperature resistance
Temperature resistance
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Radiation effects on viruses
Radiation effects on viruses
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Organic solvent resistance
Organic solvent resistance
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Viral genome structure
Viral genome structure
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Virus capsid
Virus capsid
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Single-stranded RNA (ssRNA)
Single-stranded RNA (ssRNA)
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Naked vs Enveloped Viruses
Naked vs Enveloped Viruses
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Helical Capsid
Helical Capsid
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Icosahedral Viruses
Icosahedral Viruses
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Capsomeres
Capsomeres
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Bacteriophages
Bacteriophages
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Poxvirus
Poxvirus
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Viral Envelope
Viral Envelope
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Viral Pathogenesis
Viral Pathogenesis
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Pathogenic Virus
Pathogenic Virus
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Host Entry
Host Entry
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Primary Replication
Primary Replication
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Viral Dissemination
Viral Dissemination
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Viremia
Viremia
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Extracellular Spread
Extracellular Spread
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Cytoplasmic Bridges
Cytoplasmic Bridges
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Virion
Virion
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Capsid
Capsid
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Nucleocapsid
Nucleocapsid
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Lipid envelope
Lipid envelope
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Obligate intracellular parasites
Obligate intracellular parasites
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RNA or DNA genome
RNA or DNA genome
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Antiviral drugs
Antiviral drugs
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Virus classification
Virus classification
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Orthomyxoviruses
Orthomyxoviruses
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Single-stranded RNA-RT viruses
Single-stranded RNA-RT viruses
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Double-stranded DNA viruses
Double-stranded DNA viruses
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Single-stranded DNA viruses
Single-stranded DNA viruses
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Double-stranded RNA viruses
Double-stranded RNA viruses
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Positive-sense single-stranded RNA viruses
Positive-sense single-stranded RNA viruses
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Cell cycle dependency
Cell cycle dependency
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Group V: Negative-sense RNA viruses
Group V: Negative-sense RNA viruses
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Transcription in negative-sense viruses
Transcription in negative-sense viruses
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Replication location: Non-segmented genomes
Replication location: Non-segmented genomes
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Replication location: Segmented genomes
Replication location: Segmented genomes
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Group VII: Double-stranded DNA viruses
Group VII: Double-stranded DNA viruses
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cccDNA
cccDNA
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Obligate intracellular microorganisms
Obligate intracellular microorganisms
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Brief stages of virus reproduction
Brief stages of virus reproduction
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Study Notes
Biology of Viruses
- Viruses display a wide range of shapes and sizes, measured in nanometers (billionths of a meter). They range from 20-400nm in size.
- Some viruses, like filoviruses, can be up to 1400nm in length.
- Viruses are too small to be seen with a light microscope (resolution limited to 200nm).
- Electron microscopy is often necessary to visualize viruses.
- Viruses consist of nucleic acid (RNA or DNA) surrounded by a protein coat called a capsid.
- Some viruses have an outer lipid envelope derived from the host cell membrane.
- Proteins associated with nucleic acid are known as nucleoproteins.
- The association of viral capsid proteins with viral nucleic acid is called a nucleocapsid.
- Viruses are classified by factors like core content, capsid structure, presence of envelopes, and mRNA production methods.
General Characteristics of Viruses
- Viruses are significantly smaller than prokaryotic or eukaryotic cells (0.01-0.3µm).
- Viruses lack a metabolic system and depend on the host cell's machinery for replication.
- Viruses are obligate intracellular parasites.
Virus Genome
- Viruses have either DNA or RNA genomes.
- Viral genomes minimally encode the instructions for:
- Genome replication and packaging
- Production of viral proteins
- Subverting cellular functions for virion production
- Some viruses cause cell destruction, others persist in cells, and others cause cellular transformation.
Virus Structure
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Viral structure varies from simple forms to complex shapes including helical, icosahedral, and complex structures with tails or envelopes.
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Viruses are resistant to some agents but not all.
- Temperature: Viruses are generally heat-labile (inactivated by heat).
- Radiation: Non-ionizing and ionizing radiation may cause damage and inactivation.
- Organic solvents: Solvents like chloroform, ether, and bile salts can damage the lipid envelope of enveloped viruses.
- Disinfectants: Oxidizing agents like chlorine, hydrogen peroxide, and iodine can usually destroy viruses.
Viral Chemical Properties
- Genome: Nucleic acids (DNA or RNA, but not both), linear or circular.
- Capsid: The outer protein coat protecting the nucleic acid, providing symmetry and structure basis for classification. Types of capsids include naked icosahedral, enveloped icosahedral, enveloped helical, naked helical, and complex forms.
- Envelope: Some viruses have an envelope derived from host cell membranes.
- Glycoproteins: Spike-like proteins on the envelope important for attachment and subsequent infection.
- Enzymes: Some viruses have their own enzymes, such as retroviruses with reverse transcriptase.
Viral Classification and Taxonomy
- The International Committee on Taxonomy of Viruses (ICTV) classifies viruses based on nucleic acid type, envelope presence, capsid symmetry, virion dimensions, and capsid.
- The Baltimore system classifies viruses based on their genome sequence and mRNA synthesis method. This complements the ICTV system. Several classification methods are available.
Viral Morphology
- Viruses have various basic shapes (helical, icosahedral, complex).
- Variations in morphology exist due to envelope presence (naked or enveloped).
- Key examples include enveloped helical, naked icosahedral, etc.
Icosahedral Viruses
- Most animal viruses are icosahedral (nearly spherical).
- The icosahedron is a 20-sided polygon composed of equilateral triangles.
- A specified minimum number of identical capsomeres is usually required.
- Viruses with icosahedral structures are typically released when the host cell lyses.
Complex Viruses
- Viruses have a complex outer wall or head-tail morphology.
- Often involved in infecting bacteria (bacteriophages).
- The head is icosahedral, the tail is helical.
- This morphology is used for injecting viral genetic material into the bacterial cell.
Envelope Viruses
- Enveloped viruses have a lipid bilayer membrane.
- These viruses bud from the host cell membrane as they exit.
- Viral glycoproteins on the envelope assist in attachment to host cells.
Viral Classification Based on Nucleic Acid
- The classification is dynamic.
- Viruses are characterized by their nucleic acid type (DNA or RNA), linearity, and strandedness (single or double).
Viral Replication
- Viruses attach and enter host cells.
- Genomic material is uncoated inside the cell.
- Viral components are synthesized
- New virions assemble and are released.
- Examples of modes include budding, lysis, etc.
Pathogenesis of Viral Infections
- Viral spread occurs through the bloodstream or lymphatic system (or nervous system).
- Viral replication occurs locally (at the initial site of entry), the viruses can spread systemically to other organs and tissues.
- Inflammation, cell injury, and host immune responses can cause clinical illnesses.
- Virus shedding is the release of infectious viruses in environment from infected host.
Viral Entry & Replication
- Viruses enter host cells through various mechanisms (attachment to skin, gastrointestinal tract, respiratory tract, etc.)
- Replication sites vary depending on the virus (bloodstream, liver, spleen, etc).
- The virus hijacks the host cellular machinery for its replication.
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Description
Explore the fascinating world of viruses, their structures, and classifications. This quiz delves into the sizes, shapes, and components of viruses, emphasizing the unique characteristics that differentiate them from other microorganisms. Test your knowledge on how viruses interact with host cells and their classification methods.
