Microbiology Chapter 13 Test Questions – Flashcards
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| a capsid is whatit contains whatmade of what? |
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| outer part of virus - made of protein - contains genetic material / forms shell around it |
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| explain the genetic material in a virus |
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| - either DNA or RNA - double stranded or single stranded - linear, several molecules or single and circular |
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| what 4 things make up the basic structure of a virustwo optional, the others are required |
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| capsid genetic material envelope (optional) spikes (optional) |
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| the envelops of a virus is a ______________ _________ that provides protection as well as __________ sites. does the envelope play the normal roles of a cell membrane? |
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| the envelope of a virus is a PHOSPHOLIPID BILAYER that provides protection as well as ATTACHMENT sites (OPTIONAL- only some viruses have envelopes) IT DOES NOT PLAY SAME ROLE AS CELL MEMBRANE |
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| spikes |
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| proteins that are made and attached to capsid (in an enveloped virus, it is inside envelope) - used by virus for host cell recognition |
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| there is a specific ________ cell for each virus |
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| host (host cell specificity) |
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| viruses cause infection through the _________ process. |
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| replication |
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| lytic viral replication begins with the __________ step when the virus makes contact with surface of cell. After attachment _________ begins and virus goes into cell. Next is _________ where the individual parts of virus are made. next is ______ in which all individual parts are put together and a virus is assembled. Last is _________ where the newly made virus is released. |
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| ATTACHMENT, ENTRY, SYNTHESIS, ASSEMBLY, RELEASE 5 steps (LYTIC REPLICATION) |
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| bacteriophages are _____________ specific to ____________ |
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| viruses specific to bacterial cells - NEVER have envelope - release occurs by LYSIS in bacteriophages - complex in structure -tail, tail sheath, tail pins, tail fibers. |
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| do bacteriophages have envelopeswhat replication cycle do they use? |
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| NO, never LYTIC (5 steps) |
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| Entry (step 2 of lytic viral replication) |
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| virus enters cell through process of INJECTION in which genetic material goes through tube and enters the cell |
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| viruses do not have a |
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| cellular membrane, nucleus, organelles they have envelope (but this is not same as cellular membrane) |
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| host range |
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| the range of hosts a virus is specific for |
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| a virus is called a ______ until it enters the cell where its ______ is removed |
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| virion, capsid |
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| proteins on the surface of a cell code for which specific virus can enter (viruses are host cell specific) what does this mean |
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| the virus can only attach to the host's cells which have certain proteins on the surface. (receptors) ex: aids is specific to human killer T cells, while west nile can affect different species of humans, birds, reptiles etc. |
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| are all organisms susceptible to some sort of viral attack? |
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| yes |
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| bacteriophage ___________ all bacteria, archaea, and eukaryotes together. |
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| outnumber |
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| an enveloped virus acquires its envelope from __________ during viral _____ or ______ |
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| host cell viral replication or release |
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| an envelopes glycoproteins play a role in recognition of _______ Cells |
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| host |
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| viruses cannot reproduce themselves why? |
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| because they lack the genes for all the enzymes necessary for replication and they do not possess function ribosomes for protein synthesis. viruses are dependent on hosts enzymes and organelles (host cell is forced to replicate viral genetic material and translate viral proteins including the capsomere and viral enzymes ) |
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| the replication cycle of a virus usually results in ______ and ________ of host cell this type of replication is called ____________ |
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| death and lysis lytic replication cycle |
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| a phages contact with bacterium happens how? |
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| by random collision attachment proteins of virus link with / receptor proteins on the host's cell wall. |
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| synthesis (step 3 of lytic viral replication ) |
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| - once virus has entered cell and the host cell/ bacterium loses its chromosome, the bacterium stops synthesizing its own molecules and begins synthesizing new viruses under control of the viral genome. (similar to transcription and translation except TNA is transcribes from viral DNA instead of cellular DNA) translation from host cells ribosomes results in viral proteins, including capsomeres, tail components, viral DNA polymerase, and lysozyme (all weaken bacterial cell) |
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| translation from host cells ribosomes when a virus is present results in |
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| viral proteins components of virus viral DNA polymerase and lysozyme which weaken bacterial cell |
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| assembly (4th stage in lytic viral replication) |
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| -pieces synthesized by host cell are now assembled into a new mature virion - enzymes pump genome into the assembled capsid at high pressure for some viruses |
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| transduction |
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| - error in assembly - when a capsid assembles around leftover pieces of HOST DNA instead of the intended viral DNA. - a vision formed in this manner is still able to attach to a new host by its tail fibers but it will insert host cell DNA instead of phage DNA |
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| release (step 5 of lytic viral reproduction) |
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| -newly assembled visions are released from the cell as lysozyme completes its work on the cell wall and the bacterium disintegrates. |
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| burst time |
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| period from attachment to release (for phage undergoing lytic replication) |
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| what are the two types of viral replication in bacteriophages? |
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| the lytic cycle lysogenic cycle |
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| lysogenic viral replication |
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| - infected host cells grow and reproduce normally for many generations before they lyse. - phages are called TEMPERATE PHAGES or LYSOGENIC PHAGES - can perform lytic cycle but also perform lysogeny in addition - first a vision randomly contacts host cell - the viral DNA enter the cell just as with lytic, but the HOST CELLS DNA IS NOT DESTROYED, AND PHAGES GENOME DOES NOT IMMEDIATELY ASSUME CONTROL - virus remains INACTIVE INSTEAD... and is called a prophage - the prophage ACTUALLY ENTERS THE DNA OF THE BACTERIUM, becoming a physical part of the bacterial chromosome - every time the cell replicates its infected chromosome, the prophage is also replicated -all daughter cells of a lysogenic cell are thus infected with the quiescent virus. a prophage and its descendant may remain a part of bacterial chromosome for generations or forever. - lysogenic phages may change the phenotype of a bacterium for example from harmless form to a pathogen (LYSOGENIC CONVERSION) -later the prophage might be excised from the chromosome by recombination or other genetic event. THEN IT REENTERS LYTIC CYCLE - after induction the lytic steps of SYNTHESIS ASSEMBLY AND RELEASE resume from the point at which they stopped. |
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| temperate phages>>>> which cycle? |
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| temperate/lysogenic phage>> lysogenic cycle |
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| prophage |
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| inactive bacteriophage (viral genome does not take control, and host DNA is not destroyed) - integrated virus *** bacteriophage is integrated into host cell chromosome and goes away through lysogeny |
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| a prophage remains inactive by |
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| coding for a protein that suppresses prophage genes (renders bacteria resistent to additional infection by other viruses of the same type) |
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| lysogenic conversion |
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| conversion of bacterium's phenotype to make it a PATHOGEN (it is genetically different) |
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| induction |
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| process by which a prophage is excised from the host chromosome (inductive agents include uv light, x raw, and carcinogens) *removal of viral genetic material from host cell chromosome |
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| lysogeny is a period where the virus is |
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| dormant |
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| once induction ends we enter __________ |
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| the lytic cycle again (at synthesis) |
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| what happens if the virus doesn't exit lysogeny |
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| no viruses will be made |
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| phage therapy |
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| using bacteriophage as treatment for killing bacterial cells/bacterial infection. (not used much in the US) CAN SPECIFIICALLY target certain bacteria *BENEFICIAL BECAUSE IT WOULD NEVER ATTACK OUR CELLS, they only attack bacterial cells |
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| animal virus replication |
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| 1. attachment- must be a non enveloped virus with spikes OR enveloped 2. entry- takes place along with uncoating in some cases. an animal virus enter differently depending on envelope. In NON ENVELOPED: entry happens by DIRECT PENETRATION (most similar to injection used with bacteriophage) or by ENDOCYTOSIS (taking virus into cell) which when complete leaves the virus encapsulated in the membrane, then the capsid, then genetic material. FOR ENVELOPED: it may also enter through ENDOCYTOSIS but there is the envelope membrane, capsid, then genetic material. MEMBRANE FUSION may also be done by enveloped viruses where the capsid and genetic material enter the cytoplasm of host cell. ^ in all means of entry the virus is still surrounded by lyres whether its the capsid and membrane or the capsid membrane and envelope. * AT END OF ENTRY GENETIC MATERIAL MUST BE FREE IN CYTOPLASM *uncoating required for all besides direct penetration 3. synthesis- once genetic material is in cytoplasm, synthesis starts and viral parts are made 4. assembly- virus assembled 5. release- if it is an ENVELOPED virus the envelope isn't made during synthesis so you won't see it in assembly, so where does it come from? its means of release. its mechanism of release is called BUDDING (as a virus pushes its way out, the cell membrane becomes the viral envelope. death of host cell is slower in budding because initially the host cell can make enough cell membrane to accommodate the loss but it eventually results in death. NON ENVELOPED releases by LYSIS. 3. synthesis 4. assembly 5. release |
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| in which methods of entry for replication of animal viruses is uncoating required? |
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| -endocytosis - membrane fusion (FOR DIRECT PENETRATION UNCOATING NOT REQUIRED BECAUSE ONLY GENETIC INFO ENTERS) |
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| budding |
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| how an envelope reoccurs in animal cell replication -as virus pushes out the cell membrane becomes the viral envelope. |
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| the cell membrane of host cell becomes the viral envelope in what process |
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| budding |
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| how do non enveloped viruses enter animal cells |
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| 1. direct penetration-only genetic material enters cell similar to injection for bacteriophage 2. endocytosis - taking virus into cell, encapsulated in membrane, then capsis, then genetic material |
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| how do enveloped viruses enter animal cells? |
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| 1.membrane fusion- enveloped viruses only, capsid and genetic info enter cytoplasm of host 2. endocytosis- taking virus into cell, encapsulated in envelope membrane, then capsid, then genetic material |
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| membrane fusion occurs when |
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| during viral replication in animal cells *only in ENVELOPED viruses!!!!!!! genetic info AND capsid enter host cells cytoplasm |
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| how is release during viral replication in animal cells different for enveloped and non enveloped? |
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| enveloped- release by BUDDING. the envelope is made during release by using the cell membrane as the new envelope. host cell suffers SLOWER death non enveloped- release by LYSIS |
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| animal viruses typically have ______ while bacteriophages have ____ |
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| animal- spikes or attachment proteins bacteriophage- tails |
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| what are the three mechanisms used in entry stage of viral replication in animal cells? |
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| 1. membrane fusion (enveloped only) (only genetic material) 2. endocytosis (both) (whole virus enters) (uncoating needed) 3. direct penetration (non enveloped only) (whole virus enters)(uncoating needed) |
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| The removal of a viral capsid within a host cell is called _________ |
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| uncoating |
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| latency of animal viruses |
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| during entry viral genetic material INTEGRATES INTO NUCLEUS and sometimes into the chromosomes where it REMAINS DORMANT (called latency period) *some latent viruses in animal cells do not integrate into chromosomes of host cells while in lysogenic phages they always do |
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| latency period |
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| when we carry the virus but don't show symptoms or signs (shingles, herpes, enters latent phase) |
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| latent viruses are also known as |
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| proviruses (animal virus in latency |
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| when a provirus or latent virus is incorporated into an animal cell it is __________ and does not go through __________ |
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| permanent, induction |
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| does induction occur in eukaryotes? |
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| NO |
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| an animal virus in latency is called |
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| a provirus |
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| oncolytic virotherapy |
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| using a virus to kill cancer cells, better than chemo or radiation because it specifically targets cancer cells not the entire body. |
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| how viruses cause cancer- oncogene theory |
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| examples of cancers related to viral infection- HPV, FLV, HIV, interacts with DNA and leads to cancer. two reasons why transcription and translation of protooncogene isn't taking place: 1. no promotor 2. repressor protein DNA-----| proto-oncogene|-------|repressor|------- (repressor prevents transcription and translation) for 1st hit to DNA: virus provides a promotor DNA-----| proto-oncogene (promotor provided)|-------|repressor|------- *repressor still preventing transcription and translation 2nd hit to DNA: already has a promotor present, now repressor is interrupted and not made anymore so transcriptn and translation of what is now called an ONCOGENE will take place and this cell has uncontrolled cell division. DNA-----| oncogene|-------|interupted repressor|------- |
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| what happens when a proto-oncogene on DNA has provided a promotor and the repressor has also been interrupted |
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| uncontrolled cell growth |
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| parasitic particle types |
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| -viroid: extremely small, circular pieces of RNA that cause disease in plants -prions: protein only, it is just a proteinaceous infectious agent lacking nucleic acid; causes disease in animal called sporigiform encephalopathy. they convert proteins into themselves. VERY RESISTANT |
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| sporigiform encephalophathy is caused by |
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| prions (accumulate creating holes in brain) |
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| what is the name for the parasitic particle which takes proteins and converts them to itself |
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| prions |
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| what is the name for parasitic particles which cause plant disease |
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| viroid |
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| kuru, variant cjd, and mad cow disease are examples of |
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| diseases caused by prions |
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| disease cause by prions have a ________ incubation period |
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| long |
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| kuru |
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| new guinea brain disease - caused by eating human meat, babies born after 1940 who didn't eat human meat were no longer infected -1000 times smaller than any other -prions recruit rather than reproduce |
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| oncogenes vs protooncogenes |
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| protooncogenes- inactive genes controlling cell division (as long as protogenes are repressed no cancer results) oncogenes- active genes which control cell division (inactivation of oncogene repressors cause cancer) |
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| general characteristics of viruses |
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| -acellular agents of infection - lack ability to carry out metabolic pathways - do not reproduce independently - do not individually grow in size |
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| a bacterial cell that is infected with a temperate phage in lysogeny has undergone __________ |
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| lysogenic conversion |
