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182 Cards in this Set
- Front
- Back
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What is an obligate intracellular parasite
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only grows IN the cell on on the surface or on the outside
depends on the hose for metabolism (energy production and biosynthesis) cannot grow outside the living host |
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Do obligate intracellular parasites have the enzymes or mechanisms to make ATP or for biosynthesis?
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no
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What are some ways viruses can be cultivated?
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live hosts, embryonated eggs, tissue culture
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What is an example of a virus grown in embryonated eggs?
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influenza
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What is Cytopathic Effect
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the morphology changes of tissue culture cells after viral injection
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What is a simple non cellular structure?
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single type of nucleic acid (DNA OR RNA)
protein coat some have an envelope |
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Which is more fragile: enveloped or non enveloped
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enveloped
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What is a virus with no envelope
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naked
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What is a virus with an envelope
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enveloped virus
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What is the complete infectious viral particle
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Virion
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What makes up a virion?
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single type of nucleic acid (DNA OR RNA) (ds or ss)
Some also have viral enzymes in the core Capsid (Envelope) |
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What is the protein coat of a virus
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capsid
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What does the capsid do?
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determine the shape of the virus
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What makes up the capsid
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capsomeres
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What occurs with capsomeres
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They self assemble into a capsid
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What are spikes of a virus for?
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attachment to bind to the receptor or to hold enzymres
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What shape do viruses with envelope have
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no defined shape
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What is the envelope made of
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lipids, proteins, and carbohydrates
some are covered by glycoproteinspikes |
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What is the envelope made out of originally
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the host's membrane
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Where is the virus acquired
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the host membrane (cell membrane, ER, etc)
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Is the host range specific
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yes
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What does a virus need to bind?
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a specific receptor
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What can viruses infect
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animals, plants, protists, fungi, and bacteria
ONLY a specific type of host |
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What is the virus' attachment site
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receptor of the host
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What does Hep A bind to?
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liver only
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What is the size of a virus
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10-400 nm
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Can viruses be seen with an optical microscope
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no
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What is the capsid and the nucleic acid?
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nucleocapsid
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What is a naked virus
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has no envelope
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What is an enveloped virus
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has an envelope
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What is a nucleocapsid
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nucleic acid pore plus the capsid (protein coat)
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What is a naked virus
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Virion/ whole nucleocapsid
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What is an enveloped virus?
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virion minus envelope (whole nucleocapsid minus envelope)
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What type of virus is more resistant to organic solvents like alcohol
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naked virus
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Why is the enveloped virus more fragile
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it is sensitive to solvents and chemicals because of the lipid in the envelope: When the envelope is destroyed, the virus cannot infect its host and loses attachment site
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Does the phospholipid envelope dissolve easily
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yes
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Where is the attachment site on an enveloped virus
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on the envelope
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What is the shape of helical viruses?
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rigid or flexible, sprial nucleic acid with capsomere tubing
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WHat is the shape of the polyhedral virus
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has small triangles
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Icosahedral
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20 trinagular faces and 12 corners
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what is the smallest polyhedral virus
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icosahedral
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What is the shape of a complex virus
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icosahedral head, rod shaped tail with tail fibers (base plate, tail pin)
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What are the bases for classifying viruses?
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NA type (DNA, RNA, ds, ss)
Capsid morphology (shape, size, number of capsomeres) Presence of envelope Host range Strategy for replication (classify RNA viruses) |
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What are the stages of viral replication
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attachment (of virion to host)
entry (of virion or its genome into host cell) synthesis (of viral NA and viral protein using hosts ribosomes and enzymes) assembly (of new virions) release (of new virions from host) |
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How does the attachment site for viral replication bind to the receptor?
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by a weak chemical bond
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What enters the cell in lytic replication of a bacteriophage?
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just the viral DNA, not the entire thing
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What does the viral DNA entering the cell cause?
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lysis of the hosts DNA
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Are all genes for viruses exepressed at once
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no
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When are virus genes expressed
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as needed
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What happens to the host cell in the lytic cycle
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it is destroyed (virulent or lytic phage)
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What is an example of a virulent/lytic phage?
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T even phage
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What occurs during the attachment stage of the lytic cycle?
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a weak chemical bond is formed between attachment side of virus and receptor on host; T even (tail fiber and plate), host receptor is on the cell wall
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What occurs during the entry stage of the lytic cycle?
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T even release lysozyme to weaken the peptidoglycan wall and the tail sheath contracts and injects the core protein tube into the host cell and releases DNA into the host cell
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What occurs during the synthesis stage of the lytic cycle?
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bacterial biosynthesis is shut down (host DNA degraded), viral biosynthesis beings (makes viral DNA, mRNA and proteins like enzymes and capsid protein)
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Are all viral genes transcribed at the same time?
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no
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What does early transcription make?
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early proteins, such as viral enzymes needed for biosynthesis
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What does late transcription make?
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late proteins such as capsid protein, lytic enzyme
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What occurs in the assembly stage of the lytic cycle?
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a spontaneous process:
puts together a phage DNa and a capsid to make a virion |
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What occurs during the release stage of the lytic cycle?
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T even phage produces lytic enzymes to lyse the host cell and each bacterial host releases about 100-200 new phages (however not all are perfectly assembled)
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About how many new phages are made from an animal cell?
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thousands
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What is the burst time of the lytic cycle?
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time from absorption to release
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What is the burst size of the lytic cycle?
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viral yield; the number of phages released by one host cell
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When does the lysogenic cycle go to the lytic cycle?
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when the repressor protein is gone
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What is a prophage?
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viral DNA integrated into the host genome
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What happens in the lysogenic phage?
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viral DNA stays into the host genome and divides
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What does the repressor protein do?
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prevents other viral genes from transcribing
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When may the prophage excise from teh bacterial chromosome?
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can occr naturally or caused by induction (UV light)
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What does a temperate phage do?
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lysogeny (most of the time) or lytic cycle
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What is lysogeny?
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a lysogenic phage inserts its DNA into the host genome and becomes a prophage and replicates with the host cell (lysogenic cell) for many generations without lysing the host
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a lysogenic phage inserts its DNA into the host genome and becomes a prophage and replicates with the host cell (lysogenic cell) for many generations without lysing the host
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lysogeny
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What are the phases of the lysogeny cycle?
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attachment, phage DNA enter the host, syntehsis of early protein, integration of phage DNA into host chromosome, attainment of lysogeny
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What occurs during synthesis in the lysogeny cycle?
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phage DNa makes phage mRNA which makes repressor protein which blocks transcription of other phage genes
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What affects the phage DNA entering the host chromosome?
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specific insertion site
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What occurs during attainment of lysogeny during the lysogenic cycle?
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prophage replicates as a part of bacterial chromosome, repressor protein is produced continuously to maintain lysogeny
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How long is the phage in lysogeny?
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as long as the repressor protein is present
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WHat is induction?
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when the repressor protein is inactivated and the phage operon is not repressed and it goes into the lytic cycle (may occur spontaneously or from UV)
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What does UV do to the lysogenic cycle
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it induces the production of a protease which degrades the repressor protein and causes the lysogenic phage to go into the lytic cycle
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What is generalized transduction
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mistake/ accidentally acquire bacterial dna
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What is the importance of lysogeny?
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lysogenic conversion: lysogenic cell may acquire new characteristics, lysogenic cells are immune to reinfection by the same phage, may be involved in specialized transduction
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lysogenic cell may acquire new characteristics
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lysogenic conversion
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What is the bacteria that only makes diptheria when infected with phage?
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corynebacterium diphtheria
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In what can specialized transduction occur?
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lysogenic phage
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What occurs in specialized transduction?
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accidentally cuts at a specific site and so every virus replicated contains some bacterial DNA
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What are the phases of an animal virus?
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attachment, entry, uncoating, synthesis, assembly, release
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What is the one extra stage in animal virus cycle
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uncoating
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What is uncoating?
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all of the virus enters the cell instead of just the DNA and it must be uncoated
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What occurs during attachment of the animal virus?
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binds to complementary specific receptor site on the surface of host cell
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What are ways of penetration of animal virus?
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direct penetration, membrane fusion, or endocytosis
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What is direct penetration?
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the virus directly binds to the receptor and the genome directly enters and does not need uncoated
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What is membrane fusion?
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USED BY ENVELOPED VIRUSES ONLY, the envelope and the membrane merge (because made of the same basic structure), and the protein coat is removed by viral or host enzymes
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What is endocytosis?
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phagocytosis: receptor mediated endocytosis; used by both enveloped and naked viruses; goes through phagocytosis when the virus binds to the cell
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What can use membrane fusion?
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only enveloped
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What can use endocytosis?
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enveloped and naked
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What is the uncoating stage of animal virus
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the protein coat is degraded by proteolytic enzyme (of host or virus)
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What occurs in biosynthesis of animal virus
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viral NA controls the biosynthesis in the host, to produce a new virions, the virus must replicate its genome and produce a capsid and envelope and viral glycoproteins(not all viral genes transcribed at once)
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Which will be transcribed first: genes for capsid and envelope proteins or genes for biosynthesis enzyme?
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genes for biosynthesis because it makes enzymres before biosynthesis can continue
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Where do all DNA viruses replicate DNA?
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in the nucleus (except poxvirus)
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What is the only DNA virus that does not replicate DNA in nucleus
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poxvirus
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Where is everything assembled in the poxvirus
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cytoplasm
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Where do DNA viruses synthesize viral proteins?
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cytoplasm
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What occurs in DNA virus biosynthesis?
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replicates DNA in nucleus (except for poxvirus), synthesizes viral proteins in cytoplasm, proteins enter the nucleus, nucelocapsids are assmpled in the nucleus
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What is a + RNA sense strand?
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can serve as a mRNA directly; complementary to - RNA (a template to make - RNA)
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What is -RNA antisense strand?
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cannot be a mRNA, complementary to + RNA, serve as a template for synthesis of +RNA
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What is the uncoating stage of animal virus
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the protein coat is degraded by proteolytic enzyme (of host or virus)
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What occurs in biosynthesis of animal virus
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viral NA controls the biosynthesis in the host, to produce a new virions, the virus must replicate its genome and produce a capsid and envelope and viral glycoproteins(not all viral genes transcribed at once)
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Which will be transcribed first: genes for capsid and envelope proteins or genes for biosynthesis enzyme?
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genes for biosynthesis because it makes enzymres before biosynthesis can continue
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Where do all DNA viruses replicate DNA?
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in the nucleus (except poxvirus)
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What is the only DNA virus that does not replicate DNA in nucleus
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poxvirus
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Where is everything assembled in the poxvirus
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cytoplasm
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Where do DNA viruses synthesize viral proteins?
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cytoplasm
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What occurs in DNA virus biosynthesis?
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replicates DNA in nucleus (except for poxvirus), synthesizes viral proteins in cytoplasm, proteins enter the nucleus, nucelocapsids are assmpled in the nucleus
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What is a + RNA sense strand?
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can serve as a mRNA directly; complementary to - RNA (a template to make - RNA)
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What is -RNA antisense strand?
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cannot be a mRNA, complementary to + RNA, serve as a template for synthesis of +RNA
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What is a viral enzyme needed to replicate RNA from a RNA template
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RNA dependent RNA polymerase
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What is a virus with a + ssRNA
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pico-rna-viridae
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What is picornaviridae?
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cannot carry RNA dependent RNA polymerase so it must make it first: takes +ssRNA (mRNA) to make - ssRNA which can make viral proteins or more +ssRNA
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What must carry RNA dependent RNA polymerase in capsid?
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-ssRNA because they cannot make the enzyme (not mRNA)
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Why does picornaviridae not have RNA dependent RNA polymerase in it?
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too small; must make it
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What is togaviridae?
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a + ssRNA (arthropod bone viruses) carryes the RNA dependent RNA polymerase inside
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What does togarviridae make?
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+ ssRNA to -ssRNA which make make short mRNA for envelope proteins or long mRNA for capsid proteins
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What is the whole genome: short or long mRNA?
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long mRNA
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What needs arthropod as a vector for transmission?
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togaviridae (mosquito)
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What supplies RNA dependent RNA polymerase?
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viral cell
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What must a viral cell make first?
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RNA dependent RNA polymerase unless it carries it inside
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What is the only thing that can make proteins
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mRNA
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What is retroviridae-HIV?
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a +ssRNA
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What does retroviridae-HIV carry?
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RNA dependent DNA polymerase
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What does retroviridae HIV do?
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takes + ssRNa to make cssDNA to make dsDNA to integrate into the hosts DNA as a provirus which remains latent or is transcribed into mRNA to produce more new HIV virus
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WHat occurs when retroviridae HIV is latent?
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see no new HIV products
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Where does retroviridae HIV carry RNA dependent DNA polymerase?
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in the nucleocapsid
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What is another name for RNA dependent DNA polymerase?
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reverse transcriptase
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What is a provirus similar to?
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prophage
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What is a virus with a - ssRNA?
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influenza, rhapdovirus
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What contains 8 segments of - ssRNA?
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influenza virus
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What is the virus that causes rabies?
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rhabdovirus
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What do viruses with -ssRNA absolutely HAVE to carry in nucleocapsid or they'll die?
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RNA dependent RNA polymerase
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What does -ssRNA viruses make?
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-ss RNA makes + ss RNA which makes viral proteins or makes mores -ssRNA to make new virions
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What is a virus with a dsRNA?
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reoviridae
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What is the only family with dsRNA
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reoviridae
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What is reovirus?
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respiratory, enteric, and orphan
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What does reoviridae do?
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one of capsid proteins is a RNA dependent RNA polymerase and after it enters the host +RNA is made inside capsid and released into cytoplasm
mRNA makes either viral proteins or -ssRNA which joints the +ssRNA into dsRNA |
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What type of process is assembly or maturation?
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spontaneous
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What are the 2 types of release?
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lysis of host (burst) or exocytosis (budding)
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What occurs during lysis of host?
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releases all virions at once and the host is destroyed
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What occurs during exocytosis (budding)?
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throught a special channel on the host membrane or through budding from cytoplasmic membrane (the host is not destroyed immediately: dies eventually)
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What must happen before a virus can bud out?
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must insert viral proteins into membrane
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What are the spikes on viruses?
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glycoproteins: must insert into the membrane before budding
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What is latency of some animal viruses?
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some animal viruses can remain dormant inside an animal cellas a provirus and no new viral proteins can be produced by the cell
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What are 2 examples of dormant animal viruses?
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HIV and Herpes Virsues
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What occurs in herpes virus simplex 1?
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can be activated by several stimuli: stress, fever, sunlight, trauma: lesions appear at the same spot: less severe than primary infection with shorter duration due to some immunity against it
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Where do the viruses in herpes virus simplex 1 live?
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on the nerve/ganglion forever
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What is an infectious agent made of protein PrP?
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prions
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Do prions have nucleic acids?
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no
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What occurs with prions?
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the infected host cell has a PrP protein found in brain cells of animals infect with scrapies; when normal glycoprotein (cellular PrP) contacts prion PrP, it becomes prion PrP
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What does prions cause?
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spongiform encephalitis, kuru, creuzfeldt-jakob disease, mad cow disease, scrapies
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What is spongiform encephalitis?
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large vacuoles in the brain
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What is mad cow disease
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bovine spongiform encephalitis
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How was mad cow disease caused?
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cow fed protein coming from sick infected sheep and it goes into the human when eating the cow
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WHat do normal cellular prp and prion form prp have in common?
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identical amino acid sequence
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What occurs when normal prp meets infected prp
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normal protein folds into the bad protein
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What does PrP + PrPSC make?
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2 PrP SC
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How are prions destroyed?
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burning, HCl acid, NAOH autoclave
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Do prions have nucleic acids?
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no
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What occurs with prions?
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the infected host cell has a PrP protein found in brain cells of animals infect with scrapies; when normal glycoprotein (cellular PrP) contacts prion PrP, it becomes prion PrP
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What does prions cause?
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spongiform encephalitis, kuru, creuzfeldt-jakob disease, mad cow disease, scrapies
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What is spongiform encephalitis?
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large vacuoles in the brain
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What is mad cow disease
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bovine spongiform encephalitis
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How was mad cow disease caused?
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cow fed protein coming from sick infected sheep and it goes into the human when eating the cow
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WHat do normal cellular prp and prion form prp have in common?
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identical amino acid sequence
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What occurs when normal prp meets infected prp
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normal protein folds into the bad protein
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What does PrP + PrPSC make?
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2 PrP SC
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How are prions destroyed?
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burning, HCl acid, NAOH autoclave
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Why don't prions develop in all mammals?
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only if amino acid # 129 is methionine, prp can misfold and make a prion: only 40% of humans have this type of PrP
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How many humans are susceptible to prions?
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40%
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What amino acid must a person have to get mad cow disease?
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amino acid # 129 must be methionine
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What are some ways prions are transmitted?
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ingestion of infected tissue, transplant of infected tissue, mucous membrane or broken skin contacts infected tissue
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Can cooking or normal sterilization kill prions?
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no
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How are prions destroyed?
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incineration or autoclaving in 1N HCL
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Is there a cure for prions?
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no
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What is naked circular RNA?
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viroid
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What is an infectious agent but not a virus?
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viroid
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What do viroids cause?
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plant disease only (TABLE 13.5)
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