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BI 2020
Microbiology: P5 Viruses
| Question | Answer |
|---|---|
| What are the three types of Acellular Microorganisms? | Viruses, Virions, and Prions |
| What are the 2 types of Prokaryotic organisms? | Bacteria and Archaea |
| What are a unique gourp of tiny, infectious particles that are obligate parasites of cells? | Viruses |
| Since viruses are not technically living, how do they survive in a host cell? | By regulating the functions of the host cell |
| T or F: Viruses can contain both DNA and RNA | False. They can contain either DNA or RNA but not both |
| What is the study of viruses called? | Virology |
| What are viral particles called? | Virions |
| On what scale are viruses measured (mm, um, nm, pm)? | nanometers |
| What are the 2 kinds of Covering viruses can have? | Capsid or Envelope |
| T or F: The envelope is required by all virus particles | False. It is not found in all viruses |
| What are the 3 possible components of the central core of a virus? | Nucleic Acid molecules and Matrix proteins (Enzymes not found in all viruses, but specific to its own function) |
| T or F: Viruses bear no resemblance to cells | True |
| T or F: Viruses contain protein-synthesizing machinery | False, they lack the machinery found in even the simplest cells |
| What are the purposes of the parts that make up a virus? | To invade and control a host cell. |
| What is a Capsid? | a protective protin coat made up of proteins, lipids, glycoproteins, or a combination |
| what are the 3 possible structures of a capsid? | Helical, icosahedral, or complex |
| What is an envelope? | Modified host cell's membrane--plasma membrane, nuclear envelope, ER (can take on many shapes) |
| What is a naked virion? | without an envelope |
| What is an enveloped virion? | with an envelope-surrounded by a lipid membrane |
| What are the 3 characteristics of the viral genome? | (1)Can contain only one type of nucleic acid (2)can be linear or circular (3)can be ss or ds |
| T or F: the taxonomy of viruses is similar to that of cellular organisms | True: Order, Family, Subfamily, Genus, Species |
| T or F: Approx 80 families and 4000 species of viruses are known | True! |
| T or F: The origins of viruses are entirely clear | False, there is non a single mechanisms that can account for all viruses |
| What are the 2 major classifications of viruses? | DNA viruses and RNA viruses |
| T or F: Prions are a type of viruses | False! Prions are made entirely of protein |
| How do naked viruses emerge from the host cell? | Host Cell Lysis |
| Do naked viruses contain host cell plasma membrane? | No, the cell lyses and viruses escape w/o an enveloped membrane |
| How do enveloped viruses emerge from the host cell? | Buds off of the host cell via a method similar to exocytosis |
| Do enveloped viruses contain host cell plasma membrane? | Yes. While budding off, it envelopes itself in the host membrane |
| T or F: only one virus can infect a host cell | False, numerous viruses can infect a single cell |
| T or F: viruses outnumber their host cells | True |
| T or F: viruses can contain specificity for cells they can bind to | True: some viruses are very specific and can bind to particular receptors on cell surfaces and/or some cells will not support replication |
| What is an example of a highly specific virus? | HIV; it can only infect immune cells OR Hepatitis infects only liver cells |
| T or F: Viruses can replicate outside of a host cell | False. Since viruses are obligate parasites, they require a host cell for the machinery to replicate and go through basic metabolic processes |
| T or F: Viruses contain information to make viral proteins | True, this assures replication and movement into and out of host cells |
| What are the two phases viruses can live in? | Extracellular phase and Intracellular phase |
| Describe the extracellular phase of a virus | Outside of a host cell and are metabolically inert |
| Describe the intracellular phase of a virus | Metabolically active (replication) |
| What are the modes of viral replication (5)? | (1)Adsorption [attachment] (2)Penetration (3)Replication [transcription] (4)Assembly [maturation] (5)Release |
| Describe the Adsorption mode of viral replication. | [Attachement] INITIAL CONTACT the phage collide by chance with a host cell, the base late with its tail spikes settles on the surface of the host cell |
| Describe the Penetration mode of viral replication. | Entrance of the virus OR its nucleic acid into the host cell |
| How does the penetration mode differ in plant and animal cells? | Plant cells contain a cell wall and the virus injects its genetic information into the cell through cell wall WHEREAS animal viruses enter the cell whole via phagocytosis |
| Describe the Replication mode of viral replication. | [Transcription] Duplication of viral components -- viruses inhibit the activity of the host cell |
| How do viruses inhibit the activity of the host cell during their replication phase? | The virus produces enzymes to destroy the host DNA and viral DNA takes over and begins producing proteins |
| Describe the Assembly mode of viral replication. | [Maturation] The assembling of the replicated viral components into an intact, mature virus --- the protein structures of the phage, e.g. tail, heads, tail spikes are synthesized independently of each other |
| Describe the Release mode of viral replication. | (1)Host cell lyses and releases virus into outside environment (2)Viruses leave the host cell, picking up sections of the plasma membrane-i.e.budding |
| In general, what are the 6 important steps of viral infection- | 1.DNA released and enters nucleus 2.DNA is transcribed 3.Viral mRNA is transcribed 4.Viral DNA is replicated 5.Viral DNA and proteins are assembled into a mature virus 6.Now ds, the viral DNA can insert self into host DNA |
| What are some examples of the machinery needed by a host cell? | Polymerase, transcription factors, helicase, gyrase |
| What is a replication strategy for DNA viruses infecting and animal cell? | DNA replication takes place in the nucleus and most are entirely dependent on host cell's DNA and RNA synthesizing machinery |
| What is a replication strategy for RNA viruses infecting and animal cell? | RNA replication takes place in the cytoplasm and they use their own enzymes to copy their genome |
| What is a replication strategy for Retroviruses infecting and animal cell? | synthesize DNA using their RNA genome as a template and use their own enzymes, reverse transcriptase, to copy their genome |
| What is the product of RNA and Reverse Transcriptase | cDNA (complimentary DNA) |
| What is a virus that infects bacteria called? | bacteriophage |
| What are the two cycles possible for a virus to induce the host cell to enter? | Lytic cycle and the Lysogenic Cycle |
| Describe the Lytic cylcle | The reproduction of viruses inside the host cell to destroy the cells (MAKES MORE VIRUS PARTICLES) |
| Describe the Lysogenic cycle | (hidden viruses) viruses that integrade their genetic material into the host cell genome where it may be latent (hidden), tracnscribed, or convert the host cell into a cancerous cell (INTEGRATE DNA) |
| T or F: Viral DNA can go into and out of the host DNA | True |
| What are the 3 possible results of a virus infecting a host cell? | Cell lysing releasing virions, Budding releasing virions, and integration into genome (cell modified and multiplies) |
| Describe an acute infection | usually short lived - can make you feel uncomfortable - with signs and symptoms such as tiredness, aches, coughing, and sneezing |
| What is an example of an acute infection? | the common cold |
| Describe a latent infection | after the inital infection the virus stops replication but the virus genome is not fully eradicated, the virus can reactivate and begin producing large amount of viral progeny without the host being infect by new outside virus, stays indefinitely |
| What is an example of a latent infection? | Hepatitis B, GIV, herpes simplex, varicella-zoster virus |
| Describe a chronic infection | usually develops from an acute infection and can last for days to months to a lifetime; sometimes the person is unaware they are infected buy they may still be able to transmit the infection to others |
| What is an example of a chronic infection? | Hepatitis C |
| Where does all initial cultivation of an a virus have to occur? | In an organism that was the usual host for the virus |
| Why would you cultivate a virus? (3) | (1)to isolate and identify viruses in clinical specimens (2)to prepare viruses for vaccines (3)to do detailed research on viral structure, multiplication cycles, genetics and effects on host cells |
| T or F: Cultivating viruses is easier than cultivating bacterial cells | False, because viruses need the resources of living cells for replication, the techniques for cultivating them are more complex |
| What are the 3 most common methods for culturing animal viruses | (1)embryonated eggs (2)cell culture (3)animals |
| Describe the culturing method using embryonated eggs: | an embryo is an early developmental stage comprised of rapid cell differentiation -- the exact tissue that is inoculated inside the egg is guided by the type of virus being cultivated and the goals of the experiment |
| Describe the culturing method using cell culture: | culture cells to support viral multiplication and allow for close observations/inspections of the culture for signs of infection |
| Describe the culturing method using animals: | mice, rats, hamsters, guinea pigs, or rabbits are exposed to the virus by injection |
| What are 3 noncellular infectious agents? | Viroids, Virusoids, and Prions |
| What is a short strand of RNA that lacks a capsid or other type of coating--only been associated with certain plant diseases | Viriod |
| What is made of RNAs of helper viruses, found associated with larger RNA plant viruses that provide the genetic information for their replication | Virusoids |
| What are infections agents consisting of only protein called---associated with central nervous system diseases | Prions |
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savelae
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