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CH 16
Viruses
| Question | Answer |
|---|---|
| What is required for viruses to cause disease | must enter host cell, are obligately intracellular infectious particles |
| A virion is.... | the infectious component of a virus |
| What are the first 5 key characteristics of viruses | 1. small, acellular, obligate host particle 2. has nucleic acids, protein capsid, and some have envelope 3. lack cell membrane, cytosol, ribosome, and organelles 4. use hosts metabolic pathway to reproduce 5. some have enzymes inside capsids for rep |
| What are the next 5 key characteristics of viruses | 6. infect any cell type of humans, animals, plants, and bacteria 7. cause most diseases that are prevalent in the industrialized world 8. have extracellular (viron) and intracellular state (NA only) 9. Maybe specific or general 10. smaller than cells |
| Capsids do what | protect viral nucleic acid, contain proteins used to attach to host cells that are not found in the envelope, made of capsomeres |
| capsomeres are what | proteinaceous subunits that may be made of single or multiple types of proteins and make up the capsids |
| Viral envelope | from the host's membrane system acquired during viral replication or release, |
| all viruses have capsids with RNA but not all have envelope | |
| virion | complete virus particles |
| viruses infect what type of cells | infect only particular host's cells due to the affinity of viral surface proteins for host complementary proteins |
| How do viral cells compare to human and bacterial cells in size | many times smaller and are in the nm range |
| Do viruses divide or grow | no |
| Are viruses acellular or cellular | acellular |
| viruses are obligate what? | intracellular parasites which contrast with other free-living cells. some bacterial cells are not free-living cells |
| what type of nucleic acids do viruses contain | either DNA or RNA, not both like other cells types |
| The genome of viruses | |
| What are the 5 ways viruses can be classified based on | type of nucleic acid capsid morphology presence of an envelope shape size |
| Type of viral nucleic acid show more than mother cells? | more variety in their genomes, are smaller, |
| DNA viruses are classified in what ways | ssDNA, dsDNA (linear or circular), ssDNA and ds dna (circular shaped) |
| RNA viruses are classified in what ways | ssRNA positive sense, ssRNA positive sense retroviruses, ssRNA negative sense, dsRNA segmented |
| what are the three capsid morphology | Icosahedral (20 sided polygon), helical (spiral), complex (extremely rare ex. small pox) |
| Most DNA viruses are what shaped | |
| Helical capsules are always what type of viruses | envelope viruses |
| What dictates what the overall shape of the virus? | the outermost boundary, ex: envelope or capsid |
| a virus that is does not have an envelope are called what | naked or nonenvelope |
| Non-envelope have what type of shape | |
| how many familes | |
| What 6 DNA virus families will we be covering | Poxviridae, Herpesviridae, Papillomaviridae, Adenoviridae, Hepadnaviridae, Parvoviridae |
| What 9 RNA virus families will be covering | |
| How do you know that a name signifies a family | has -idae suffix |
| What are the 4 major steps for animal viruses | 1. Attachment to host cells 2. entry into host cells and uncoating 3. synthesis of viral proteins and genetic materials 4. assembly and release from host cell |
| Attachment to host cells is performed by what mechanisms | chemical attraction btw viral proteins and cell receptors glycoprotein spikes or other attachment molecules that mediate attachment |
| Entry into host cell is performed by what three different mechanisms | Direct penetration, membrane fusion, or endocytosis |
| In direct penetration what occurs, | DNA injected directly into host cell, but the entire capsid does not enter the host cell |
| What entry mechanisms do envelope viruses use | membrane fusion or endocytosis |
| What is the viral envelope made of | phospholipids |
| In membrane fusion what occurs | capsid enters the cell, while envelope integrates with host cell membrane, host cell protease enzymes break capsid and release nucleic acid, |
| In endocytosis, what occurs for the p? | similar to phagocytosis. will be packaged in an endosome/phagosome inside the cell, breaks out of endosome although still in virion form, |
| How are viral proteins produced after the virus is inside the cell | DNA replication or transcription will occur in the nucleus, so viral DNA will travel to nucleus to use enzymes to undergo replication and transcription, mRNA will be produced with viral genes, mRNA will be translocated into ribosomes for translation |
| in Assembly and release what occurr? | newly translated proteins are packaged and released |
| For RNA viruses, where do they replicate | in the cytoplasm |
| What are the four types of RNA viruses | +ss RNA, -ssRNA, dsRNA, retroviruses |
| How do most RNA viruses enter the host cell? | most enter through endocytosis or membrane fusion |
| after entry has occurred, what occurs next for RNA viruses | RNA virus removes capsid, positive sense RNA directly translated in the ribosome of the host, negative sense is converted to positive sense RNA in ribosome, final product are viral enzymes, capsid proteins, spikes, |
| positive sense RNA is synonymous with? negative sense RNA is synonymous with? | mRNA. 2) Complementary RNA |
| if virus contains its own enzymes what may occur | RNA is replicated in host cytosol using viral RNA polymerase |
| What occurs as the RNA leaves the cell | it picks up segments from the host's cell membrane and spike proteins creating an envelope with spike proteins. |
| for retroviruses what enzyme do they contain | |
| What affects the number of viruses reproduced | type of virus, size, initial health of host |
| How are envelope viruses released? what can result from this? | via budding, which can result in persistent infections |
| How are naked viruses released | by exocytosis or lysis, produce damage |
| How are host cells killed | through constant lysis and interfering with host cell metabolism |
Created by:
Acrob89
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