Introduction to Viruses, Viroids, and Prions Practice Flashcards

This set of 30 vocabulary flashcards covers the fundamental concepts of viral structure, classification, multiplication cycles, and non-viral infectious agents as presented in the lecture notes.

Robert Koch

Identified the pathogens responsible for causing tuberculosis, cholera, and anthrax.

Filterable agent

A term used by Friedrich Loeffler and Paul Frosch in $1898$ to describe the cause of certain diseases that could pass through specialized filters.

Obligate intracellular parasites

A property of viruses meaning they require a host cell to multiply and are inactive macromolecules outside of the host cell.

Ultramicroscopic

The general size of most viruses, which are usually less than $0.2\,\mu\text{m}$ and range in diameter from $20\,\text{nm}$ to $750\,\text{nm}$.

Capsid

The protein shell that surrounds the nucleic acid core of a virus particle.

Nucleocapsid

The structure formed by the viral capsid together with its enclosed nucleic acid.

Naked viruses

Viruses that consist only of a nucleocapsid and lack an external covering or envelope.

Capsomers

Identical protein subunits that serve as the building blocks for the viral capsid.

Helical capsid

A structural type of capsid consisting of a continuous helix of capsomers forming a cylindrical nucleocapsid.

Icosahedral capsid

A three-dimensional, symmetrical polygon capsid with $20$ sides and $12$ evenly spaced corners.

Envelope

An external covering acquired by mostly animal viruses when they leave the host cell, composed of a lipid bilayer.

Spikes

Exposed proteins on the outside of the viral envelope that are essential for the attachment of the virus to the host cell.

Positive-sense RNA

Single-stranded RNA (ssRNA) genomes that are ready for immediate translation into proteins.

Negative-sense RNA

Single-stranded RNA (ssRNA) genomes that must be converted into the proper form before translation can occur.

Polymerases

Pre-formed enzymes required for viral replication that synthesize DNA or RNA.

Reverse transcriptase

An enzyme used by the HIV virus for the synthesis of DNA from an RNA template.

Adsorption

The phase of the viral multiplication cycle where the virus attaches specifically to receptor sites on the host cell membrane.

Fusion

A method of penetration where the viral envelope merges directly with the host membrane via lipid rearrangement.

Endocytosis

A penetration method where the entire virus is engulfed and enclosed in a vacuole or vesicle by the host cell.

Budding

A release mechanism for enveloped viruses where the nucleocapsid binds to the membrane, which pinches off to shed the virus without immediate cell destruction.

Cell lysis

The process by which nonenveloped and complex viruses are released from a host cell by rupturing the membrane, resulting in cell death.

Cytopathic effects

Virus-induced damage to cells that alters their microscopic appearance, such as changes in size, shape, or the development of intracellular changes.

Syncytia

A cytopathic effect where multiple host cells fuse together to form large, multinucleated giant cells.

Oncogenic viruses

Animal viruses that enter a host cell and permanently alter its genetic material, potentially leading to cancer.

Transformation

The effect on a cell caused by oncoviruses, resulting in increased growth rates, chromosomal alterations, and indefinite cell division.

Bacteriophages

Viruses that specifically infect bacteria, such as those that infect Escherichia coli.

Prophage

An inactive state of a temperate phage where the viral genome is inserted into the bacterial host genome.

Lysogeny

A condition in which the viral DNA is retained and copied during normal bacterial cell division, spreading the virus without killing the host.

Prions

Misfolded infectious proteins that contain no nucleic acid and cause fatal neurodegenerative diseases like Creutzfeldt-Jakob Syndrome.

Viroids

Short pieces of infectious RNA that lack a protein coat and have only been identified as pathogens in plants.