Microbiology Flashcards
(215 cards)
Viruses are obligate intracellular parasite. what does that mean?
they are only able to reproduce within cells
it relies on host machinery
T/F
Viruses on their own are able to synthesis ATP and other chemical reactions.
False
T/F
Viruses are not cells or living organisms.
True
How can some viruses have ATP stored in their capsid? What can they use it for?
they got it from the last host
they can use it for penetration into the next host
When a virus is not inside a host cell, what does it contain?
only its own genome which could be single stranded or double stranded, linear or circular
If the ratio of adenine to thymine in a DNA virus is not one to one, what can be said about the genome of this virus?
the genome must be single stranded DNA, or RNA which has no T
A disease agent that is isolated from a human cannot reproduce on its own, but it can reproduce when put in a culture of human cells. In its pure form it contains both RNA and DNA, is it a virus? Why?
no because a virus can only have DNA or RNA but not both
What is a bacteriophage?
virus that infects bacteria
What limiting factor affects all viral genomes?
size
What happens if a viral genome triples in size?
it will no longer fit within the normal viral structure and therefore will not be packaged in infectious viral particles
How does the virus adapt to its size constraint?
- carries only a few genes and relies mostly on host encoded proteins for transcription, translation, and replication
- ability to encode more than one protein in a given length of genome by utilizing more than one reading frame within a piece of DNA so that genes overlap
How do ribosomes used to translate viral proteins compare to host ribosomes?
they are the same because viruses use the host ribosomes
What is the protein coat that surrounds the viral nucleic acid genome which is also used to classify viruses?
capsid
Helical capsids?
rod shaped
Polyhedral capsids?
multiple sided geometric figures with regular surfaces
What is the capsid shape of Bacteriophage T4?
Helical and Polyhedral
What is the host for the Bacteriophage T4?
E. coli
Where on the capsid is the genome located?
in the capsid head
What do the tail fibers and the base plate of the capsid do?
attach to the surface of the host cell
What does the sheath of the capsid do?
contracts using energy of stored ATP, injects the genome into the host
Why might a bacteriophage inject its DNA, while animal viruses do not?
a phage must puncture the bacterial cell wall, while animal viruses can be internalized whole because there is no cell wall
The entire viral capsid is composed of _______ while the viral genome is composed of ______.
proteins
nucleic acids
In animal viruses, what surrounds the capsid?
the envelope
What is the envelope?
membrane on the exterior of the animal virus derived from the host membrane