L20,Viral structure

Viruses vary in size from approximately 18 nm (parvoviruses) to 300 nm (poxvirus), with some like the mimivirus being 400 nm.

Viruses can have either RNA or DNA as their genomic material.

Structural proteins are present in the virion structure of the virus.

Nonstructural proteins are used for the replication of the virus.

No, viruses arose at different times during evolution and have no common ancestor.

Viruses cannot be easily classified based on genetic relatedness as many appear to have arisen independently.

The highest classification for viruses is order or family.

No, species are not named in the Linnaean binomial system.

Species may be subtyped into types and isolates (strains) based on relatedness.

It means 'small RNA' virus.

It refers to the fact that the virus goes in reverse, making DNA from RNA.

It refers to 'adenoids'.

It stands for 'respiratory, enteric, orphan'.

They refer to the GI tract.

For example, 'norwalk virus' is named for Norwalk, OH, and 'coxsackievirus' for Coxsackie, NY.

By physical and biochemical characteristics such as size, morphology, type of genome, and means of replication.

Order (-virales)

(-viridae)

(-virinae)

(-virus)

dsDNA viruses (e.g. Adenoviruses, Herpesviruses, Poxviruses)

ssDNA viruses (+)sense DNA (e.g. Parvoviruses)

dsRNA viruses (e.g. Reoviruses)

(+)ssRNA viruses (+)sense RNA (e.g. Picornaviruses, Togaviruses)

(-)ssRNA viruses (-)sense RNA (e.g. Orthomyxoviruses, Rhabdoviruses)

ssRNA-RT viruses (+)sense RNA with DNA intermediate in life-cycle (e.g. Retroviruses)

dsDNA-RT viruses (e.g. Hepadnaviruses)

Enveloped and Naked capsid.

Pox, Herpes, and Hepadna.

Polyoma, Parvo (ss), Papilloma, and Adeno.

(+RNA), (-RNA), (+/-RNA), and (+RNA via DNA).

Picorna and Calici.

Toga, Flavi, Corona, Rhabdo, Filo, Orthomyxo, Paramyxo, Bunya, and Arena.

They have a double capsid.

They replicate via a DNA intermediate.

Lipid envelope, protein capsid, nucleic acid, virion-associated polymerase, and spike projections.

It provides a protective outer layer and helps in the attachment to host cells.

It protects the viral genetic material and aids in the delivery of the nucleic acid into host cells.

They facilitate the attachment and entry of the virus into host cells.

It is involved in the replication of the viral nucleic acid within the host cell.

It can be either DNA or RNA, depending on the type of virus.

A protein shell surrounding the genome of a virus.

The nucleic acid-protein assembly within a viral particle, used when referring to a discrete substructure.

A host cell-derived lipid bilayer that surrounds some viruses.

An infectious virus particle.

Protection of the genome.

By assembling a stable protective protein shell.

They are involved in specific recognition and packaging of the nucleic acid genome.

They interact with host cell membranes to form the envelope.

Delivery of the genome.

They bind host cell receptors.

Uncoating of the genome.

Fusion with cell membranes.

Transport of genome to the appropriate site.

The virus particle.

It serves as the package, protection, and delivery vehicle during transmission of the virus from one host to another.

It mediates the attachment of the virus with the target cell.

A structure formed by the association of capsid or nucleic acid binding proteins with the genome, which may be surrounded by an envelope.

A nucleic acid genome, a protein coat (capsid), and possibly an envelope.

Viruses can have RNA or DNA as their genome.

DNA in viruses may be single or double stranded, linear or circular.

Positive-sense RNA can serve as mRNA and is immediately translatable by host cell ribosomes.

Capsid proteins are assembled from individual proteins into progressively larger units, helping to keep the virus genome smaller by using the same gene.

Capsid proteins associate into sub-units, then protomers, then capsomers, and finally a procapsid or capsid.

A PAMP (Pathogen associated molecular pattern) is a repetitive capsid structure that allows the virus to be recognized by the immune system.

The simplest symmetrical structures include helical and icosahedral structures.

A cluster of L1 molecules represented by triangles of varying colors.

A pentagonal shape composed of five colored triangles, labeled as 'Capsomere'.

Interconnected pentagonal shapes resembling capsomeres, forming pentavalent and hexavalent capsomers.

A spherical structure formed by interconnected capsomeres, labeled as 'Capsid'.

Pentagonal and hexagonal structures.

Poxvirus

Because capsids must self-assemble.

They can serve as the basis for antiviral vaccines, such as the HPV vaccine.

Via cell lysis, which exposes them to antibodies after lysis.

It protects the genome and contains the viral attachment protein (VAP), dictating the tropism of the virus.

Lipids, proteins, and glycoproteins in a membrane structure similar to host cell.

Generally round or pleomorphic, with exceptions like rhabdovirus (bullet-shaped) and poxvirus (complex, brick-like shape).

The capsid lies under the envelope.

Majority have traditional icosahedral or helical morphology.

Usually contains few host proteins, which are excluded during assembly.

Hemagglutinins.

Enveloped.

The genome.

Influenza, Rabies, HIV, Herpes.

It has a multi-layered structure with hemagglutinin and neuraminidase spikes.

It appears rod-shaped with a rounded end and a textured surface.

They are spherical and closely packed with envelope spikes protruding from the surface.

It has an irregular shape with glycoprotein spikes on the envelope and a core called the nucleocapsid.

Any substance that causes red blood cells (RBCs) to agglutinate.

Hemagglutination or haemagglutination.

They act as receptors for attachment and can agglutinate red cells.

Influenza hemagglutinin.

Measles hemagglutinin.

It acts as a hemagglutinin on the virus surface.

Mumps virus.

It is the process by which viruses attach to red blood cells, causing them to clump together.

The initial interaction where the viral receptor interacts with the cell membrane and the viral particle is enclosed within a capsid.

The cell membrane curves around the viral particle, creating a bud.

The viral particle is fully budded and enclosed by the cell membrane, completely detached from the original cell.

The viral gene, tegument, and capsid are visible within the virus particle.

Syncytium formation.

They fuse to form a larger cell called Syncytium.

It represents the viral genome.

Host-cell receptor and viral fusion protein.

An infectious, obligate intracellular parasite comprising genetic material (DNA or RNA) surrounded by a protein coat and/or a membrane.

Viruses replicate by assembling parts, while bacteria reproduce by binary fission.

A phase where no infectious particles are detected as the virus is assembling inside the host cell.

The number of infectious particles rises sharply after the Eclipse period and then levels off.

The steady increase in cell numbers over time due to bacterial growth and division.

It refers to the original terminology used to describe viruses that can pass through filters designed to retain bacteria.

Because they do not grow, do not produce or store energy by themselves, and are not functionally active outside a cell.

Obligate, intracellular parasites.

Viruses are ubiquitous and infect every living organism, making up the largest biomass on earth.

Viral components, once made, must self-assemble.

Negative-sense RNA must be transcribed to mRNA before it can be translated into protein and must carry an RNA polymerase with itself when infecting a cell.

Ambisense RNA contains both positive and negative regions of RNA attached end-to-end.

RNA may be segmented into pieces, with each piece coding one or more genes.

10^-8 to 10^-11.

They can be proofread by host cell mechanisms.

10^-3 to 10^-4.

They lack the proofreading capability that DNA genomes have.

dsDNA, gapped dsDNA, ssDNA, dsRNA, ss (+) RNA, ss (-) RNA, ss (+) RNA with DNA intermediate.

A rigid structure able to withstand harsh environmental conditions.

Drying, acid, and detergents.

They can pass through gastric acids and bile and can be passed fecal-orally.

Naked viruses.

A membrane with lipids, proteins, and glycoproteins.

By budding through the host cell membranes, thus containing host cell structures.

They can release via budding without necessarily killing the host cell, allowing viruses to spread directly from cell-to-cell.

Cell-mediated immunity, as enveloped viruses may not be exposed to antibodies.

Drying, acidic conditions, detergents, and solvents.

In fluids, respiratory droplets, blood, and tissue, as they need to remain wet.