Viruses and Prions

Vocabulary flashcards covering viral replication, capsid structures, host cell effects, bacteriophage life cycles, and prions based on Chapter 5 lecture notes.

Filterable virus

An infectious agent present in host fluids that remains infectious after passing through porcelain filters designed to trap bacteria.

Obligate intracellular parasites

Agents that cannot multiply unless they invade a specific host cell and instruct its genetic and metabolic machinery to build and release new viruses.

Virion

A single, fully formed infectious virus particle with an exterior protective protein capsid and genetic material.

Capsid

The protective protein shell that packages, protects, and surrounds the viral genome, making up the bulk of a virion's mass.

Capsomeres

Individual protein subunits that assemble spontaneously to construct the viral capsid.

Helical capsid

A virus structure formed by rod-shaped capsomeres that bond together to create a hollow, cylindrical tube enclosing the genome.

Icosahedral capsid

A three-dimensional, 20-sided polygon viral capsid structure formed by capsomeres in a symmetrical pattern.

Complex capsid

A viral capsid structural arrangement that deviates from pure helical or icosahedral forms, often possessing additional structures like tails and baseplates.

Enveloped virus

A virus surrounded by a flexible lipid-based outer layer acquired by budding off from a host cell membrane.

Naked virus

A nonenveloped virus that lacks an outer lipid membrane surrounding its capsid and is typically released from host cells via cell lysis.

Spikes

Glycoprotein extensions protruding from the viral capsid or envelope that aid in host cell recognition, attachment, and entry.

Positive-sense RNA

Single-stranded viral RNA that is immediately available for host cell ribosome translation into viral proteins.

Negative-sense RNA

Single-stranded viral RNA that must be copied into a complementary mRNA molecule by viral RNA-dependent RNA polymerase prior to translation.

Segmented genome

A viral genome setup in which individual genes exist on separate, distinct pieces of RNA.

Retrovirus

An RNA virus carrying reverse transcriptase to synthesize viral DNA from its RNA genome once inside a host cell.

Adsorption

The viral attachment stage where specific glycoprotein spikes on the virus bind directly to complementary protein receptors on the host cell membrane.

Host range

The spectrum of host cell types or species that a specific virus is capable of binding to and infecting.

Tropisms

The specificities of individual viruses for binding to and infecting distinct tissues within a host organism.

Endocytosis

A viral penetration pathway where an entire virus particle is engulfed by the plasma membrane and enclosed within a vacuole or vesicle.

Uncoating

The step in animal virus replication where host or viral enzymes break down the protein capsid to release the viral genome.

Cytopathic effects (CPEs)

Virus-induced cell damage that visibly alters the microscopic appearance of infected host cells.

Inclusion bodies

Compacted masses of viruses or damaged cell organelles that accumulate in the nucleus or cytoplasm of infected cells.

Syncytium

A single large multinucleate cell formed by the fusion of multiple damaged adjacent host cells during viral infection.

Provirus

Viral DNA that has integrated directly into the chromosomal DNA of the host cell, leading to persistent infection.

Oncovirus

An oncogenic virus capable of transforming host cells and inducing cancer.

Transformation

The effect of oncogenic viruses on host cells that causes chromosomal alterations, surface modifications, rapid growth, and indefinite cell division.

Bacteriophage

A virus that infects and parasitizes bacterial cells.

Lytic cycle

A phage replication process where newly formed virions are assembled inside the host bacterium, culminating in host cell lysis and viral release.

Lysogenic state

A condition in which a temperate phage incorporates its genetic material into the host bacterial chromosome as a prophage without immediately lysing the cell.

Prophage

An inactive form of a bacteriophage genome integrated into specific sites on a host bacterial chromosome.

Lysogenic conversion

The acquisition of new traits or capabilities, such as toxin production, by a host bacterium from genes on an integrated prophage.

Prion

A noncellular, nonviral infectious agent composed entirely of protein that causes neighboring normal proteins to misfold, leading to transmissible spongiform encephalopathies.