Chapter 13 (EXAM 4) Flashcards
What is a virion ?
A complete virus that contains nucleic acids on the inside and a protein coat on the outside, capsid
What is a virus
an obligate intercellular parasite, non living structure ( dont have cell structures)
Requires a host cell for reproduction and in order to obtain the raw materials necessary to build a new virus
Nucleic acid is either DNA ORRR RNA not both
What does a complete virion contain
The core, genetic material and a capsid on the outside, protein coat
What is the capsid
A protein coat used for attachment and protection of nucleic acid from host cell enzymes
Some have an additional envelope on the outside made of phospholipid molecules obtained from exiting a host cell
What are the different shapes of the capsid
polyhedral=many faced, helical=cylindrical
Describe helical viruses
More cylinder shaped, important viruses: rabid, influenza(enveloped), ebola
Describe polyhedral viruses
Have many faces, 20 and 12 corners, important viruses: herpes(enveloped), Adeno, polio
What is a complex virus
Bacteriophage
HAs regions that are polyhedral and regions that are helical
Have extra materials that allow them to land on top of a bacterium and inject genetic materials rather then being taken into the cell
Virus vs Bacteria
VIRUS
Intracellular parasite No cell membrane, ribosomes No binary fission Does not generate ATP Does not work against antibiotics Has working interferons
Virus vs Bacteria
BACTERIA
Not an intracellular parasite, but Rickettsia Chlanydiae is an exception Has cell membrane and ribosomes Binary fission occurs & generates ATP Works against antibiotics Has no interferons working
What is a bacteriophage
A virus that infects bacteria
What is an intracellular ?
A virus that is inside of the host cells, aka ALL VIRUSES
What is a host range
The organism that the virus can affect and the range of tissue they affect
Only affect plants, animals or certain tissue
Describe the Lytic cycle
- Phage attaches to the host cell
- Penetration occurs; phage penetrates host cell and injects DNA. The capsid stays outside
- Biosynthesis; Makes cell host synthesize viral components. Core and capsid are made and need to be put together
- Maturation; Viral components are assembled
- Release; Host cell lyses and new irons are released
What does Lytic mean
To cause post cell death. in order for capsid to attach to bacterial cell wall there has to be a sugar protein interaction
When do viral genes occur
during biosynthesis. Involved in synthesis of core
When do late genes occur
during biosynthesis. contain recipe on how to make the capsid
What is the Eclipse period
Period between infection and virion completion
What is the burst time
The time it takes from attachment to being released from a cell, can be hours to minutes
What is the burst size
Number of phage particles/viruses being released when going out of a cell
Where does virus replication occur
In the cytosol, is messy because lots of the core and capsid is made but fewer complete viruses so there are lots of leftovers in the cytosol
Describe the Lysogenic cycle
Another means of viral multiplication, referred to as the temperate cycle
The host cell will recover, not be destroyed like in the lytic
1. Phage attaches to host cell and injects DNA
2.Phage DNA enters lysogenic phase
3.Genetic material can then be recombines with the host genome; prophage
4. The repressor proteins keep the virus and prophage quiet but certain chemicals and UV light will cause it to pop out making the virus active and enter lytic cycle
What are the 3 possible results after lysogenic (temperate) infections
- Immunity to reinfection by the same exact virus
- Phage conversion, host cell is changed bc of presence of viral genes
- Specialized transduction, host cell is changed bc of bacterial genes brought in by the virus from a previous infection
Describe transduction
When the first bacterium has been infected by the virus, recombination occurs and the prophage is now inside
Something causes genetic makeup to pop out but gal genes are brought out with it
host cell machinery is used to replicate and exit moving onto second bacteria where it will inject its genetic material
Both sets of genes recombine into the host genome and the prophage remains quiet
If the genes seem useful they will keep the genes, if they’re not the bacterium will discard extra genes
What are gal genes
Transcribe enzymes to break down the lactose/sugar
Bacterial virus vs Animal virus
BACTERTIAL
Attachment: tail fibers attach to cell wall proteins
Entry: by injection into the host cell, capsid remains outside
uncoating: not required bc DNA was injected
biosynthesis: occurs in cytoplasm
Release: Lysogenecy; when virus leaves the host cell is destroyed
Bacterial virus vs Animal virus
ANIMAL
Attachment: no cw so attachment happens on the plasma mambrane and glycoproteins
Entry: Capsid enters by endocytosis or fusion cell
Uncoating: Capsid gets removed bu being enzymatically digested
Biosynthesis: Occurs in nucleus ( DNA) then in cytoplasm(RNA)
Release: Latency; sloe viral infections, when the virus leaves it will either bud our or rupture plasma membrane. and destroy cell
What is Endocytosis
The process of entering the cell
What does it mean to be receptor mediated
When the cell indents and surrounds the virus, taking it in
What is fusion
When the enveloped virus is released with the capsid and the core directly into the cytoplasm
What is Exocytosis
Reffered to as budding, when the virus buds out of the cell
If cell membrane is taken the host cell will survive
If the cell membrane is not taken with it, the virus will kill the cell bc of so many holes in the cell from leaving
What is uncoating
What happens inside of the cell when the host cell enzymes have to digest the capsid ( protein coat )
Describe biosynthesis
Requires host cell machinery in order to make the viral parts
When the virus comes in, it chops up the host DNA so host cell parts only pay attention to viral DNA
This begins the transcribing of viral parts; transcriptase
Describe Transcriptase
When essential RNA polymers, viral DNA with the use of transcripttase, create RNA.
Describe Viral multiplication in animal cells
- Attachment: Virion attaches to host cell
- Entry & Uncoating: Virion enters cell and DNA is uncoated ( lysosomal enzymes digest protein capsid)
- Early genes are transcribed
- Biosynthesis:Viral DNA is replicated and vital proteins are made
- Late genes are transcribed, capsid proteins synthesized
- Maturation: Virions mature and assembly occurs
- Release: Visions are released
What is reverse transcriptase
Enzyme that allows RNA virus to make itself into DNA
What is a provirus
A virus that infects bacteria in an animal
What is a retrovirus
Viruses that use reverse transcriptase to make themselves into DNA ( HIV )
Describe an RNA virus
Some have the ability to transcribe additional pieces of RNA ( - or. + strands )
-: serve as a template to make more positive strands
+: has 2 functions; serve as template to make more + & - strands
can be incorporated to capsid to make a complete iron
could serve as messenger RNA
Repliacted in cytoplasm
Describe a DNA virus
Have to replicate in the nucleus
Capsid is made in the cytoplasm and has to migrate to nucleus for assembly before leaving the cell as a complete virion
DNA virus vs RNA virus
DNA VIRUS
IS replicated in nucleus
Capsid is made in the cytoplasm
Once the capsid is made it has to migrate to DNA in the nucleus before it exits the cell
DNA virus vs RNA virus
RNA VIRUS
Replicate in the cytoplasm
Capsid is made in the cytoplasm
RNA and capsid are made in the cytoplasm and maturation and assembly
Have extra pieces of genetic material, + & - strands
What can viruses do when they generate disease
- Cause circumvention: go around the hosts ability to fight off virus
- CPE: Cytopathic effect, used for just viruses
- Loss of contact inhibition: when cells contact one another/touch each other, they re inhibited from utilizing all the resources just for themselves
- syncytium: fusion of cells from multi nucleic mass. measles, herepes and mumps cause this
- Permeability: selective in what they allow but some viruses can allow the cell membrane permeability to change so cells are no longer selective
- AG changes: Ability to generate antibiotic changes in cells which makes body recognize a cell as being foreign
- Interferons: A/B/G antiviral proteins // stimulate phagocytes to clean up mess of viral parts after a viral infection
- Inclusions body: Vessicles, inside the host cells after a virus has infected them ( left over viral parts)
- DNA changes: DNA can be turned off so it no longer produces certain proteins, can be changes to other viruses and can change cancer causing genes to turn on
- Cellular functions:
What is a latent virus
A virus that causes outbreaks with occasional symptoms
Cold sores, Leukemia, Shingles (Caused by herpes virus, immunocompromised get this, inflammation and oozing on one side of the body)
looks like a hill on a graph
What is a Persistent virus
A virus that builds up over time
Cervical cancer, HIV/AIDS, Liver cancer
looks like a 120 degree up facing v on a graph
What are oncogenic viruses
Viruses that could cause cancer
When it infects a host cell, it causes chromosomal changes in the cell; transformation
Explain transformation
When the host cells try to tell the immune system they’re messed up by putting antigens on their surface, TSTA antigen or T-AG antigen
Describe the TSTA antigen
Tumor specific transplantation antigen
Antigen that an infected cell outs on its surface to alter the immune system that its not functioning in the body, chromosomes have been messed up
What techniques do you need to know to be able to identify a virus
- Morphology of the virus, shape of capsid
- What kind of core it has, DNA or RNA, single stranded or double?
- What organism it infects, ecological niche
- Its strategy for replication, lytic, lysogenic
What techniques are used to identify a virus
Plaque method, Embryonate eggs, Animals, Cell cultures
Describe the plaque method technique
Used to identify bacteriophages
Create a bacterial laden and spread bacteria by using tiny glass beads
The virus will leave a clearing area
Describe the embryonate eggs technique
Can be used to study viruses
Virues can be infected and researchers can see:
-certain tissue or cell damage
-poxs in membrane
-If membrane has died
Vaccines have been developed using these eggs
Describe the animal technique
Used to study viruses
Look for signs and symptoms in the animals
look at tissue damage/ malfunction and do biopsy to determine virus
Describe the cell culture technique
An ideal way to study viruses because they are obligate intercellular parasites
- Tissue is treated with enzymes to separate the cells
- Cells are suspended in multure medium
- Normal cells will grow in monolayer, the cells that have been transformed will appear in a multilayer stack
What is a primary cell line
From a cell culture
Made from tissue slices, they die out in a few generations
What is a secondary cell line
From a cell culture
Diploid cell lines, made from human embryos, last for about 100 generations
What is a continuous cell line
From a cell culture
Immortal cell lines, made from cancer cells, H.L cells are still being used to study and proliferate viruses in a laboratory setting
What is a viroid
A short makes RNA plant virus
Do not have a capsid
What are virusoids
RNA plant viruses with a capsid
When/how does a plant get a virus
Through an insect or through breakage in the plant tissue
What are prions
Infectious protein particles
abider 18-20 predations diseases
What is ensepalothopy
Gotten from prions, create holes in the neurological tissue
Known as mad cow disease
Causes other proteins to become diseases, causing more death in the brain
Can obtain from digesting it
