Term
acellular
parasites
don't divide or grow
obligate intracellular parasite
contain either RNA or DNA
proteinaceous capsid around genome |
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Definition
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Term
viruses cause most of the infectious diseases that still plague the industrialized world
consist of a protein coat
capsid - made of protein subunits called capsomeres
the nucleic acid and capsid are called a head or nucleocapsid
most viruses infect only particular host's cells |
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Definition
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Term
extracellular = virion
intracellular = virus |
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Definition
| what is the intracellular and extracellular states of a virus called? |
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Term
oral-fecal
airborne
sexual
blood borne
congenital |
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Definition
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Term
DS DNA undergoes transcription into mRNA (mRNA is transcribed from viral DNA) which undergoes translation into proteins (translation by host ribosomes) that the virus needs for assembly and release from the host cell
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Definition
| mechanism of viral mRNA, protein synthesis, and genome replication of a virus with DS DNA |
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Term
positive strand RNA acts as mRNA directly and is translated (through host ribosomes) into proteins that the virus needs for assembly and release from the host cell
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Definition
| mechanism of viral mRNA, protein synthesis, and genome replication of a virus with positive SS RNA |
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Term
negative strand viral RNA acts as a template to make mRNA. This mRNA is then translated (through host ribosomes) into proteins that the virus needs for assembly and release from the host cell
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Definition
| mechanism of viral mRNA, protein synthesis, and genome replication of a virus with negative SS RNA |
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Term
retroviruses use reverse transcriptase to go from SS RNA to DS DNA. DNA is transcribed into mRNA that is translated (through host ribosomes) into proteins that are needed for viral assembly and release from the host cell
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Definition
| mechanism of viral mRNA, protein synthesis, and genome replication of a retrovirus |
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Term
HELICAL: capsomeres that bond in spiral shape as a tube around nucleic acid
POLYHEDRAL: many sided
ENVELOPED: spherical
COMPLEX: many different shapes |
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Definition
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Term
virion without an envelope is naked
lack a true cell membrane but may have cytoplasmic membrane (an envelope) around capsid
lipid bilayer is studded with glycosylated membrane proteins (spikes or knobs)
glycoproteins are used for attachment, release, recognition
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Definition
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Term
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Definition
viruses cannot reproduce themselves.
they don't have genes for all the enzymes necessary for replication or the ribosomes for protein synthesis
replication often results in death of the host cell, so it is called ( ) replication |
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Term
ATTACHMENT of the virion to the host cell
ENTRY of the virion or its genome into the host cell
SYNTHESIS of new nucleic acids and viral proteins by the host's enzymes and ribosomes
ASSEMBLY of the new viruses within the host cell
RELEASE of the virions from the host cell
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Definition
| steps to lytic replication |
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Term
virions are non-motile
attachment depends on chemical attraction and precise fit between attachment proteins on the phage's tail and complementary receptor proteins on the host's cell wall, flagella, pili |
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Definition
| mechanism of viral bacteriophage attachment to a host cell |
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Term
upon contact with the cell wall, the virus releases lysozymes, a protein carried within the capsid which weakens the peptidoglycan of the cell wall
the phage's tail sheath contracts, forcing a hallow tube through the cell wall and cell membrane
virus's genome is pushed through the tube. |
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Definition
| mechanism of viral bacteriophage entry into a host cell |
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Term
viral enzymes degrade the host's DNA into nucleic acid
DS DNA viruses: undergo protein synthesis like cellular transcription and translation BUT mRNA is transcribed from VIRAL DNA, not cellular. Translation by host's ribosomes results in viral proteins such as head capsomeres, tail components, lysozymes, DNA polymerase |
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Definition
| mechanism of viral bacteriophage synthesis once in a host cell |
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Term
| polymerases, then capsid protomers and scaffolding proteins |
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Definition
| what are the first proteins generated in viral bacteriophage synthesis? |
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Term
| virions are released as lysozyme degrades the cell wall and bacterium |
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Definition
| mechanism of viral bacteriophage release from a host cell |
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Term
many bacteria are becoming resistant to antibiotics, this is a way to overcome some resistance
able to target specific bacteria
fewer side effects due to selective toxicity
less disruption of normal flora
easy to mass produce and cheap |
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Definition
advantages of Rx bacteriophages (viruses to kill bacteria)
EXAM ESSAY QUESTION |
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Term
animal viruses lack tails and tail fibers (that bacteriophages have)
animal viruses have glycoprotein spikes or other attachment molecules |
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Definition
| mechanism of attachment of animal viruses |
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Term
1) direct penetration: naked viruses (non-enveloped), genome enters, capsid remains
2) membrane fusion: entire capsid and genome enter (nucleocapsid), viral envelope fuses to host membrane
3) phagocyotsis: host cell phagocytizes whole virus
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Definition
| 3 mechanisms of animal viruses entry into host cells |
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Term
DS DNA similar to normal replication
SS RNA (retroviruses like HIV) use a DNA intermediary that is transcribed from RNA by reverse transcriptase (capsid enzyme). DNA used to synthesize additional RNA for new HIV |
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Definition
| mechanism of synthesis of animal viruses |
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Term
most DNA viruses assemble in and are released from nucleus
RNA viruses in the cytoplasm
takes longer than bacteriophages (herpesvirus takes about 1 day to replicate, bacteriophages take 20 minutes) |
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Definition
| where does assembly occur for animal DNA viruses and animal RNA viruses? |
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Term
extruded through membranes: nuclear, cytplasmic, endoplasmic reticulum = acquire viral envelope
enveloped viruses often released via budding which allows infected cells to remain intact
naked viruses extruded by exocytosis or causes lysis and cell death
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Definition
| mechanism of release of animal viruses from the host cell (difference between enveloped viruses and naked viruses) |
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Term
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Definition
viruses that remain dormant in cells
viral activity is random |
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Term
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Definition
| infections with enveloped viruses in which the host cells shed viruses steadily and slowly |
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Term
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Definition
result in cell death and spread to surrounding tissues
pathologic damage often due to immune response to viral antigen and epitopes on surface of infected cells
especially true with chronic infections with constant virus production |
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Term
immunomodulators
interferons are an example |
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Definition
| substances that modify the response of immune competent cells through signaling mechanisms |
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Term
interferons (IFN) are a class of cytokines
IFN allows cells to develop an antiviral state - replication of the virus is inhibited
restrict viral growth at - penetration, uncoating, synthesis of mRNA, protein synthesis, and assembly
most nucleated cells make IFNs
IFNs bind to specific receptors on ADJACENT CELLS to protect them from viral infection
IFN also enhance expression of MHC I and II molecules, which then increases viral antigen presentation to specific T helper cells or cytotoxic T cells
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AVP = antiviral protein |
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Definition
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Term
genital herpes
VZV
influenza
prophylactic for CMV
genital warts
chronic hepatitis B virus |
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Definition
| TEST QUESTION: give examples of an infection that an interferon has been approved for clinical use |
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Term
| C3d complement receptor on B lymphocytes |
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Definition
| what is the target receptor for the Epstein Barr virus? |
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Term
| persistence in erythrocytes that establishes prolonged viremia |
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Definition
| which property of the virus of Colorado tick fever enables its transmission from mammals to ticks? |
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