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med micro 22 chapter
chapter 13
| Question | Answer |
|---|---|
| Definition of Viruses | Obligate intracellular Parasite |
| Characteristics of Viruses | Unable to exist independently from host cells. Can direct life processes of host cells. Contain a sngle type of nucleic acid (DNA or RNA) and a protion coat, sometimes enclosed by an envelope composed of lipids, proteins, and carbohydrates |
| What does obligate mean? | Absolutely must |
| Size of Viruses | Smallest infectious agents must have electron microscopes to see. From 20nm to 450 nm in diameter |
| Components of a virus particle | A Cellular contains only the parts needed to invade and control a host cell. |
| 2 main components of a virus particle | Central Core and External Covering |
| Central core contains? | Nucleic acid and preformed enzymes. |
| Characteristics of the Nucleic acid in a virus? | has DNA or RNA not both. genome (genes of organism) size is very small. |
| What are the minmum genes contained in the Nucleic acid in a virus? | Capsid synthesis, nucleic acid synthesis, regulation of host processes (home invasion gene) and virus packaging |
| Do all Viruses contain preformed enzymes? | No |
| What are some examples of preformed enzymes that may exsist in viruses? | polymerases, replicases and reverse transcriptase |
| What is the external covering of a virus called? | Capsid |
| What is the Capsid? | Protein "shell" that surrounds and protects nucleic acid. Helps introduce nucleic acid into host. Stimulates immune system. |
| What is a "nucleocapsid"? | Capsid and Nucleic acid equals "nucleocapsid" |
| What are subunits of Capsids called? | Capsomers they self assemble to form helical or icosahedral structures |
| What is the virus envelope? | External layer in some viruses. Derived from host cell membrane when viruses are released. Glycoprotein "spikes" on outside of envelope play a role in attachment of viruses to host cells. |
| Two requirements for viral multiplication | requires a host cell and viruses must be able to appropriate the synthetic and genetic machinery of host |
| Steps in Viral Multiplication | Adsorption, Penetration, Replication, Assembly and Maturation and Release |
| What is a Bacteriophage? | Viruses that infect Bacteria |
| What are the 2 multiplication cycles in Bacteriophages? | Lytic Cycle and Lysogeny |
| What is the Lytic cycle? | Replication of viral nucleic acids and proteins causes cell to be packed with virus. Causes lysis and death of host cell |
| What are the sequence of events in the lytic cycle? part 1 | Bacteriophage tail fibers bind to receptors on bacteria. Viral nucleic acid is injected through bacterial wall and membrane. |
| What are the sequence of events in the lytic cycle? part 2 | Viral nucleic acid redirects genetic and metabolic activities of cell. Viral subunits spontaneously assemble. Host cell lyses liberating virions. |
| What is the main difference in Lytic cycle and Lysogeny? | "temperate" bacteriophages undergo adsorption and penetration but are not replicated or released. Host cell is not lysed |
| Lysogeny is equal to? | Latency |
| Examples of Lysogenic phages are? | Herpes Viruses, cold sores shingles |
| Other characteristics of lysogeny are. part 1 | Viral DNA is inserted into bacterial chromosome. Prophage is retained by bacterial cell and is copied during cell division. progeny also carry temperate phage. |
| Other characteristics of lysogeny are. part 2 | Viral genome is not expressed. Prophage in lysogenic cell can be excised from host chromosome and initiate lytic cycle. |
| A complete, fully developed viral particle composed of nucleic acid surrounded by a coat is known as? | Virion |