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Ch. 10 Questions
Microbiology
| Question | Answer |
|---|---|
| Because viruses are incapable of replicating outside of a host, they are called---------? | obligate intracellular parasites |
| What is the size of the largest virus? | 1/25 the size of the smallest bacterium |
| What are bacterial viruses called? | bacteriophages or just phages |
| How does a bacteriophage penetrate the host cell wall? | in addition to attachment factors--often have a needlelike tube used to propel through bacterial envelope & inject their nucleic acid into the host cell |
| Capsomere | viral protein that forms the coat around the viral nucleic acid |
| Capsid | protein shell made of capsomeres |
| Necleocapsid | capsid covering plus the nucleic acid |
| Envelope | additional covering made of membrane from the host cell and viral proteins |
| Virion | intact viral particle with its appropriate coating layers |
| Icosahedron | twenty identical sides |
| List the 2 main components of nucleocapsids | capsid and nucleic acid |
| What are nonenveloped viruses called? | naked viruses |
| The placement of viruses into families depends upon which characteristic? | structural features--general size & shape--whether they are naked/enveloped--is nucleic acid DNA/RNA |
| What part of the envelope comes from the host cell and what part from the virus? | membrane is from the host cell and the attachement proteins are from the virus |
| What type of molecule in an enveloped virus is necessary for attachment to the host cell? | viral attachment protein that protrudes outside of the viral envelope |
| Adsprption of the virus to the cell depends upon what specific viral and cellular components? | viral attachment protein and a cell receptor |
| What are two types oof penetration? | endocytosis and membrane fussion |
| Where and how does the process of uncoating take place? | uncoating is the removal of the viral capsid protein by cellular enzymes in the cell cytoplasm |
| Where does DNA and RNA replication take place? | cell nucleus for DNA and in the cytoplasm for RNA |
| Where does viral translation occur? | host cytoplasm |
| How does the assembly of intact virions occur? | proteins from the coating vind to each other and to proper nucleic acid--enables nucleocapsid to zip together without outside energy |
| Describe how the release of virions can occur by cell lysis or budding. | naked virus simply lyses the cell to release virions--enveloped virus acquires membbrane from the host as it passes through the cell membrane |
| How many phages/virions can be produced in a single growth cycle? | about 100 phages per bacterium--about 300,000 animal virions per animal cell |
| What are the differences between lytic and lysogenic viruses? | Lytic always kill the host cell by breaking it open--lysogenic enter cell where DNA integrates into host cell--becomes part of it--divide with the cell--if host cell becomes sick lysogenic viruses lyse and escape dying cell |
| What are cytopathic effects? | when a viral specimen is placed on human tissue cells in a culture medium--cytopathic effect is visible changes, microscopic/otherwise in cells resulting from viral infection |
| What is a plaque? | specific type of CPE where cells are killed so loss of cells gives rise to a hole in the cell layer |
| How is the inclusion body type of CPE observed? | normally seen in the microscope as dark areas of viral material |
| What are the resulting large cells called when many cells fuse together as a result of viral infection? | syncytia or giant cells |
| What changes occur during transformation? | viruses cause the cells to keep growing uncontrollably and pile up or form a tumor |
| What do viruses do to the host DNA-sythesizing machinery? | subvert the host cell machinery into making viruses rather than cellular materials |
| What type of nucleic acid is in a virion? | either RNA or DNA but not both |
| Why is tumorigenesis only associated with DNA viruses or retroviruses? | only occurs when a cell's genes are altered to cause uncontrollable cell division--only DNA can integrate into cell's chromosome--chromosome is DNA |
Created by:
heatherlvn
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