Chapter 19 (The Virus) Flashcards
Are viruses cells?
no, they are called “intracellular parasites”
What is a dead cell?
a cell that has no more of a capacity to make energy
What types of cells do viruses infect?
they are able to infect EVERY single type of life form, a virus can infect one type of cell or organism but not others
what macromolecules are viruses made of?
nucleic acids and proteins
What is unique about how viruses survive?
they evolve very fast which is driven by the mistakes in the genetic blueprint that don’t have a mechanism to get fixed
What do viral genomes consist of?
double or single-stranded DNA or RNA and sometimes a viral envelope
What is the capsid?
the capsid is the protein shell that encloses the viral genome
What is the capsid built from?
capsomere proteins
Some viruses also have these that contain capsid
some viruses also have lipid membranes that contain capsid
What is the lipid membrane in some viruses called?
viral envelope
What are the benefits of a lipid membrane in some viruses?
entry/attachment into the healthy cell plasma membrane
What are the viruses that infect bacterial cells?
bacteriophages
What are the two reproductive mechanisms for viruses?
lysogenetic and lytic cycle
What is the lytic cycle?
it destroys the host cell almost immediately
What types of phages use the lytic cycle?
virulent phages, able to spread more
What is the cycle of the lytic cycle?
attachment, injection of DNA, digestion, production, release of progeny viruses
As a defense, what do cells have?
restriction enzymes
What can restriction enzymes do?
they can degrade foreign nucleic acids at a specific part of the sequence
What is the lysogenic cycle?
replicates the genome without destroying the host cell
What types of phages use the lysogenic cycle?
temperate phages, they have the ability to stay dormant
What does the lysogenic cycle ensure?
ensures the virus is made more frequently
What does the lytic cycle ensure?
ability have viruses spread, be more viral
What is the cycle of the lysogenic cycle?
copies phage and host DNA passes phage DNA to daughter cell
What are antibiotics?
drugs that clear an infection
What is the problem with antibiotics?
viruses can have a resistance to each increased dosage and keep mutating
How are bacteriophages beneficial to fighting bacterial infections?
able to infect bacteria since they are bacteria’s natural predators with high target specificity
Most viruses are based on what genome in animals?
RNA based
How do RNA viruses infect animals (3 ways)?
1) directly
2) template for more RNA
3) template for DNA (make info flow backward)
What are RNA viruses that make a template for DNA using reverse transcriptase?
retroviruses
What enzyme do retroviruses use?
reverse transcriptase
What are proviruses?
viral genome integrated into DNA of the host cell PERMANENTLY and FOREVER, the cell’s enzymes transcribe the DNA into RNA and the RNA is used to make viral proteins and as new viral genomes
What is the retrovirus genome?
RNA
What does the enzyme in the retrovirus do?
cuts proteins, makes a different variety of the same sequence
What enzyme do retroviruses use to cut/break proteins?
protease
What is the most common/famous example of a retrovirus?
HIV
What is the lifecycle of a retrovirus (explain using HIV)?
the retrovirus adhere to host cell
go through capsin
reverse transcriptase makes hybrid of RNA and DNA (making DNA)
remanents of the instructions of virus stays in nucleus
new capsid made using host cell’s plasma membrane
What does HERVs stand for?
Human endogenous retroviruses
How do HERVs get passed down (in terms of gametes)?
retrovirus infects one gamete cell of human parent, offspring has virus in all cells of body, offspring pass down possibility of getting that virus to future generations
How are two ways HERVs affect the human population?
they can either result in loss of population OR stayed fixed in a population by being in all humans
What are emerging viruses?
viruses that seem to appear suddenly (but already existed)
What are the three ways that viruses emerge?
1) human interconnection
2) enter new host species
3) mutations
How do viruses emerge through human interconnection?
one human spreading virus to another human and then goes on exponentially (globally)
How do viruses emerge by entering new host species?
viruses can jump from an animal to a human or from one bird to a pig for example
How do viruses emerge by mutations?
viruses make changes in their profiles as they keep replicating
- there is an uncertainty into how it will affect us and what kind of change that is
How is the flu classified by?
hemagglutinin (surface glycoprotein) and neuraminidase (an enzyme used for virus to exist in the cell)
What is herd immunity?
passing down the ability to fight off a virus over generations and as a community
What are prions?
misshapen proteins that are able to pass their shape onto normal proteins and they cause brain disease in animals
What is a famous disease caused by prions?
mad cow disease
