MicroBio Ch. 5 - Viruses & Prions

poison

'Virus' means what in Latin?

Segmented

A term that refers to when individual genes exist on separate pieces of RNA; potential for lots of recombination!

icosahedral

Adenovirus is an example of a naked ___________ virus. In the photo you can clearly see the spikes, some of which have broken off. [ADD IMAGE]

1 protein shell 2 nucleic acid

Basic structure of a virus consists of ___ ___ (or capsid) surrounding the ___ ___ core.

helix

During the formation of the nucleocapsid (of Helical Capsids), these discs link with other discs to form a continuous ____ into which the nucleic acid strand is coiled.

direct

Even though viruses do NOT exhibit most of the life processes of cells, they can ______ them, and thus are certainly more than inert and lifeless molecules

Ivanovski and Beijerinck

Name the two Russian microbiologists who showed that a disease in tobacco (AKA Tobacco Mosaic Virus) plants was caused by a virus.

Structure, Chemical, Similarities

Newer classification systems of Viruses emphasize the following: Hosts and diseases they cause, ______ (e.g., capsid shape, envelope), ______ composition of genome, and ______ in genetic makeup. (Think: HD,SCS)

naked helical virus

Tobacco mosaic virus, which attacks tobacco leaves is a primary example of what kind of virus?

icosahedrons

Two very common viruses, hepatitis B virus and the herpes simplex virus, possess enveloped _______. [ADD IMAGE]

have no cytoplasm, no cell membrane, no ribosomes or organelles of their own

Name the four structures Viruses LACK regarding their compact and economical structure

DNA or RNA

Nucleic acid of viruses can be either ____ or ____, but not both.

1 multiply 2 host

Obligate intracellular parasites refer to microbes that cannot _______ unless they invade a specific _______ cell and instruct its genetic and metabolic machinery to make and release new viruses.

Complex capsids

Refer to a a capsid structure only found in the viruses that infect bacteria, may have multiple types of proteins and take shapes that are not symmetrical. They are never enveloped

Icosahedral Capsids

Refer to a a three-dimensional, 20-sided figure with 12 evenly spaced corners. The arrangements of the capsomeres vary from one virus to another

Retroviruses

Refer to a group of viruses that carry their own enzymes to create DNA out of their RNA.

RNA viruses

Refer to can be double-stranded, but more often single-stranded

obligate intracellular parasites

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

DNA viruses

Refer to single-stranded (ss) or double-stranded (ds; linear or circular)

peplomers

Refer to the spike-like molecules on virus surfaces that give them high specificity for attachment to host cell

Naked

Refer to viruses that consist only of a nucleocapsid

Envelopes

Refers to the external covering of a capsid, usually a modified piece of the host's cell membrane

capsid

Refers to the protein shell surrounding the nucleic acid core of a virus's basic structure

Loeffler and Frosch

Regarded as the first virologists, _______ & ______ discovered a human & animal virus that causes foot-and-mouth disease in cattle.

transcriptase

Reverse _____________ synthesizes DNA from RNA.

infectious molecules

Since viruses are unable to multiply independently from the host cell, they are not living things and should be called __________ ___________

naked or enveloped

Spikes can be found on _____ or ________ viruses and are essential for attaching to host cell receptors for Viral Replication.

T (True)

T or F: For many years, animal viruses were classified on the basis of their hosts and the diseases they caused, but are not part of the 5 Kingdom or 3 Domain taxonomic schemes

F (False)

T or F: If the virus spike(s) cannot find a host cell receptor to bind to, then infection and viral replication will still occur.

T (True)

T or F: The vast majority of viruses completely lack the genes for synthesis of metabolic enzymes and thus they depend on the host's enzymes and machinery

naked helical

The nucleocapsids of _____ _____ viruses are very rigid and tightly wound into a cylinder-shaped package.

Complex capsids

The one pictured is a T4 bacteriophage. They have specialized spikes which are elongated and called tail fibers. They also have a tail pin that is essential for penetrating of their host.

Filterable

The presence of _______ Viruses proved that an infection could be caused by a fluid containing agents smaller than bacteria.

Helical Capsids

The simpler ____ _____ have rod-shaped capsomeres that bond together to form a series of hollow discs resembling a bracelet.

Replicases

These enzymes are for specific operations within their host cell that copy RNA- more commonly called RNA dependent RNA polymerases.

Polymerases

These enzymes are for specific operations within their host cell that synthesizes DNA.

Louis Pasteur

This man proposed the term virus, which is Latin for "poison"

Enveloped Capsids

This type of morphology is found in several enveloped human viruses, including influenza, measles, and rabies.

cells

Viruses NOT ______ by definition; their structure is very compact and economical.

1 multiply 2 genetic

Viruses ______ by taking control of host cell's _______ material and regulating the synthesis and assembly of new viruses - it thus degrades the host DNA into fragments.

ubiquitous

Viruses are _____ in nature (e.g., air, soil, and water) and hosts in all domains.

ultramicroscopic

Viruses are __________ in size thus requiring high level magnification microscopy using electrons in order to be visualized.

active or inactive

Viruses are better described as _______ or _________ rather than "alive or dead" because they are obligate intracellular parasites

parasites

Viruses are obligate intracellular ________ of bacteria, protozoa, fungi, algae, plants, and animals; thus, they can infect all groups of living organisms

inert

Viruses do not independently fulfill the characteristics of life (or living) and are metabolically _____ when outside of a host cell

FOUR

Viruses have _____ variations of Nucleic acids in that they can be double or single-stranded DNA; or, single or double-stranded RNA!

cytoplasm, membrane, ribosomes, or organelles

Viruses have no ________, cell ________, ________, or ________ of their own.

every type

Viruses infect ____ ____ of cell, including bacteria, algae, fungi, protozoa, plants, and animals

enzymes

Viruses lack _______ for most metabolic processes

Filterable virus

When fluids from host organisms passed through porcelain filters designed to trap bacteria, the filtrate remained infectious.

APUSAR

Your acronym for the General 5 phases of the animal viral replication cycle

Enveloped

____ helical nucleocapsids are more flexible and tend to be arranged as a looser helix within the envelope.

glycoprotein spikes

______ ______ exist on the surfaces of viruses and bind to host cell receptors

Spikes

_______ (aka peplomers) can be found on naked or enveloped viruses and are essential for attaching to host cell receptors and initiating viral infections in specific hosts

Louis Pasteur

_______ ______ hypothesized that rabies was caused by a "living thing" smaller than bacteria

Viruses

________ are better described as active or inactive rather than "alive or dead" because they are obligate intracellular parasites.

Positive

________-sense RNA are ready for immediate translation; their RNA = mRNA

Viruses

_________ are ultramicroscopic in size thus requiring high level magnification microscopy using electrons in order to be visualized.

Spikes (aka peplomers)

_________ project from the nucleocapsid or the envelope and Allow viruses to dock/attach with host cells

Negative

_________-sense RNA must be converted to positive RNA (mRNA) before translation can occur

Nucleocapsid

refers to the capsid together with the nucleic acid

Capsid

refers to the protein shell that surrounds the nucleic acid, made of capsomeres (number of repeating proteins)