Flashcards in Lecture 14 Deck (60):
What is even the smallest bacteria capable of?
independent replication, synthesis of energy and proteins, cell enclosed with DNA and RNA
What do viruses not have?
cell wall, cytoplasm, ribosomes/mitochondria, nucleus, independent replication
Does nature have RNA carrying genetic information?
NO- not found in nature
Will viruses contain DNA and RNA?
Not both at the same time- one or the other
DO RNA viruses carry genetic information?
Can virues synthetize their own energy or proteins?
Can viruses be seen under a microscope?
NO- too small
How do antibiotics affect viruses?
THey are resistant to all antibiotics
What did Geirer and Schraman do?
extracted the infectious nucleic acid which produced disease in the host cells confirming it as living chemicals
Most viruses are what shape?
extracellular virus particles- vary in size from 20-300nm
What is the biggest virus equal to?
the size of the smallest bacteria (micro plasm)
List shapes of viruses
spherical, complex, bullet shaped/brick shaped
What can viral nucleic acids be extracted with?
What parts make up the viral structure?
central nucleic acid, protein coat (capsid), some may have an envelop
What part of the virus protects the nucleic acid and is the basic structure of a virus?
capsid- facilitates absorption
What is the envelop of the cell made up of?
envelop is a lipid layer derived from host cell during budding
Are viruses heat labile?
At what temperature are viruses inactivated within a few seconds?
56 degrees celcius
What inactivates viruses?
sunlight, UV light
What are viruses resistant to?
chemical disinfectants- lysol for example
How doe viruses replicate?
disassemble into patricles inside the cell, multiply separately and then assemble- one virion giving rise to hundred of virion particles
Process of adsorption of a virus
virus adsorbed to host cell- there are specific receptors on host cell for viruses
Penetration of a virus
penetrate into the cell
Uncoating of a virus
stripping of virus from capsid by lysozyme of the cell
Process of virus attacking
absorption, penetration, uncoating, biosynthesis, maturation, release
Process of biosynthesis of virus
synthesis of enzymes for stages of viral replication, assembly and release. Followed by synthesis of nucleic acid and capsid protein takes place separately
Where does synthesis of nucleic acid take place?
Where does synthesis of viral proteins occur?
Where does RNA viruses synthesize nucleic acid and proteins?
Process of maturation of virus
nucleic acid and viral proteins assembled together and form viral particle
Process of release of virus
done by cell lysis (non enveloped virus) or budding (enveloped virus)
Replication times for human virus
Replication time for baceria
define Lysogenic cycle
alternate pathway of viruses in which viral genome (DNA) becomes integrated with host cell genome and multiply along with it
Name for the integrated viral DNA
What is the lysogenic cycle well studied for?
transferring of a gene
why would a virus infected cell undergo death of cell?
inhibition of protein, nucleic acid synthesis
list morphological changes of a viral infected cell
inclusion bodies, fusion of virus infected cells to form multinucleated giant cells, cytopathic effect, malignant transformation and cellular proliferation, no morphological/functional change
define cytopathic effect
darkening and rounding which may culminate in lysis/giant cell formation
forms of transmission of virus
through respiratory tract, skin, conjunctiva, genital tract
How are viruses spread person to person?
through respiratory tract, saliva, blood or semen, fecal contamination of water and food
How are viruses spread from mother to baby?
placenta or breast milk- vertical transmission
How are viruses spread animal to human?
by vectors (ex. yellow fever)
In what disease is virus spread systemically through body?
What does cell killing result in?
loss of function and symptoms
non specific host defense against viral infections
interferon, NK cells, fever
Specific defense against viral infections
humoral Antibiotics & CMI
What is the main defense mechanism in viral infections?
define Natural Killer Cells
a type of T lymphocyte that recognize virus infected cells and kill them
glycoproteins produced by leukocytes (neutrophils) during viral infection
What eliminates non specific visions?
fever- especially help enveloped virions
4 types of specific antibodies
IgA, IgM, IgG, and IgE
What does IgA protect?
respiratory and gastro infections
What does IgM and IgG protect?
against viruses entering blood
What do antibodies do?
neutralize viruses, facilitate phagocytosis, interferes with adherence and penetration, cause lysis of virus infected cells
What cell causes cell mediated immunity?
cytotoxic T cells- killing viral infected cells
What antibodies for passive immunity?
IgG and IgM