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Ch 28.5
Exam 2: Viruses
| Question | Answer |
|---|---|
| Viruses are not classified with organisms because they are _____ | non-cellular (They are about the size of a protein; They can be purified and crystallized and then stored just as chemicals are stored) |
| Protein coat called _____ | capsid |
| Capsid surrounds _____ | genetic material, either DNA or RNA |
| – Attachment sites (of some kind)- recognize and stick to ______ on the cells that they can infect. | receptors |
| Viruses do not have _____ and _____ | NO organelles; NO metabolism, few or no enzymes, not much to go wrong. |
| Viruses infect all sorts of cells – from bacteria cells to human cells – but each type is... | very specific in what it attacks (ex: Bacteriophages attack only bacteria) |
| Icosahedral in shape | Capsid |
| Acts as a syringe to inject the viral DNA into the cell | Tail sheath |
| Have attachment sites on the ends | Tail fibers |
| Life cycle of a bacteriophage: | Attachment, Penetration, Biosynthesis, Maturation, Release |
| Attachment | Tail fibers stick to receptors |
| Penetration | Tail sheath injects DNA |
| Biosynthesis | Viral DNA takes over; (Makes enzymes to break down host DNA, then uses the nucleotides for its own replication; Makes proteins for its own structure) |
| Maturation | viral proteins assemble |
| Release | Viral enzymes destroy the cell membrane and escape |
| RNA viruses that attack animal cells and have a DNA stage | Retroviruses |
| Retrovirus examples | HIV (Human Immunodeficiency Virus); Certain forms of cancer are caused by retroviruses |
| Retroviruses contain an enzyme called... | reverse transcriptase which makes DNA from the virus’ RNA |
| The viral DNA is then inserted into... | the host cell’s DNA |
| The viral DNA remains in the host cell’s DNA and is... | replicated when the host cell’s DNA is replicated |
| When the host cell’s DNA is transcribed... | then new viruses are created by the making of viral RNA |
| HIV which causes aids: develops... and attacks... | an envelope from the membrane of its last host cell; white blood cells |
| 2 things even smaller than viruses | viroids and prions |
| viroids | Circular strands of RNA that invade the nuclei of plants and cause some plant diseases |
| prions | Protein particles that are mis-shaped; Cause other proteins in the host cell to become mis-shaped and therefore non-functional |
| Prion example | Mad Cow Disease; When humans eat beef from cattle with Mad Cow Disease they can develop a disease that causes paralysis and death; Mad Cow Disease has not been found in the U.S. |
Created by:
chelsea_2010
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