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31 Cards in this Set
- Front
- Back
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What are viruses?
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Miniscule, acellular infectious agents carrying one or several pieces of either DNA or RNA
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Viruses cannot...
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carry out metobolic reactions, grow in size, respond to their environment, or reproduce independently.
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Why do most viruses only infect particular types of a host's cells?
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Due to the affinity of the viral surface proteins and glycoproteins to the complementary proteins or glycoproteins on the host cell.
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Outside the host, viruses are called?
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virions.
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What is a caspid?
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a PROTEIN coat that surrounds and protects the nucleic acid (viral genome). Sometimes provides means for host cell attachment.
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When inside the host cell, viruses...
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Shed their protein caspids and exist as naked nucleic acids.
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The viral envelope
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composed of phospholipid bilayer and proteins
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glycoprotein spikes
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proteins on the viral envelope encoded by the viral genome.
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How are viral envelopes acquired?
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From host cell during viral replication. Enveloped animal viruses surround themselves in
stolen membrane material that looks like the host cell! |
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glycoprotein spikes
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proteins on the viral envelope encoded by the viral genome.
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Viral genetic material may be...
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DNA, or RNA never both. Single stranded or double stranded DNA or RNA. Multiple linear fragments or single circular molecule. Much smaller than cellular genomes.
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Viruses differ in...
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genetic material, structure of caspid, hosts, size and shape, and presence or absence of envelope.
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Viral replication depends on?
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The host cell's organelles and enzymes to produce new virions
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Lytic Replication
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Destructive replication that results in death and degradation (lysis) of host cell.
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Five stages of lytic replication of BACTERIOPHAGES.
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Attachment, entry, synthesis, assembly, and release.
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Burst Time
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period of time required to complete entire lytic process, from attachment to release
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Burst Size
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total number of new virions released from a given population of lysed bacterial cells
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Lysogenic Replication
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Extended period of DORMANCY initiated by certain bacteriophages.
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Latent Replication
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Temporary or permanent DORMANCY elicited by certain types of animal viruses.
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Animal Virus Replication
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Use lytic replication. Differ in the presence of a viral envelope, eukaryotic nature of cells, lack of cell wall in animal cells.
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Attachment of Animal Viruses
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mediated by glycoprotein spikes or other attachment molecules on capsid or envelope
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Entry Mechanisms include...
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direct penetration for non-enveloped viruses, and membrane fusion phagocytosis for enveloped viruses.
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Synthesis of Animal Viruses
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synthesis strategy dependent on its nucleic acid (DNA or RNA; single stranded or double stranded)
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DNA viruses are assembled in and released from...
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nucleus into cytosol
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enveloped viruses caused persistent infections because they are
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released slowly from the host cell, budding on by one.
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This may be prolonged for years with no viral activity, signs, or symptoms
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Latent Replication of Animal Cells
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Neoplasia
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Uncontrolled cell division in multicellular animal; mass of neoplastic cells is a tumor.
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Prions
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infectious agents composed of single protein (PrP)
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Excess PrP production or mutations in PrP gene result in initial formation of
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Prion form of PrP (disease causing form with beta sheets)
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Prion diseases are only destroyed by?
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INCINERATION
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Prion Diseases
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involve neurological degeneration, deposition of fibrils in brain, and loss of brain matter
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