virus-detailed Flashcards
what is a virus?
a virus is a pathogenic particle which acts as parasite and capable of replication only within a host cell
what is a parasite?
organism that lives in or on a host
what does it mean by viruses are obligate intracellular organism?
carry out reproduction by parasitizing host cells
what is a host cell?
a living organism which provides food and shelter for growth of other organisms such as parasites
what is a vector?
living organisms that transmits the infectious agent such as virus from one infected organism to another
describe in detailed the structure of a virus
- contains a nucleic acid core which could either be DNA or RNA
- nucleic acid core contains virion associated polymerase which has a role in genome replicate and transcription
- a protein coat called capsid protects the nucleic acid and together the protein coat and genome make up the nucleocapsid
- the capsid is made up of protein sub unit, known as capsomeres
- a phospholipid layer containing protein spikes for attachment on receptor of host cell
where exactly does the protein spikes of viruses attach to?
1- protein which act as receptor
2- lipids
3- carbohydrate chain found on glycolipid and glycoproteins
what is the typical size of a virus?
20 to 200 nanometer usually
what are the 2 main morphology of viruses and describe?
helical
-the capsomeres spiral up with the genome within the center
icosahedral
- contains 6 faces and protein spikes
what is a virion?
an infectious virus particle which is complete containing capsid, nucleic acid or even a phospholipid layer
what is a viral?
infectious agent which has a high level of redundancy
*2 or more genes perform the same biochemical function
what is a viroid?
an infectious virus particle which is in complete, only containing RNA without a protein coat
what is a proteolytic enzyme?
protease enzyme which break down or build up proteins
describe the general virus replication
1- virus attaches and enters host cell
2- disassembly of the virion occurs, revealing its nucleic acid, protein, etc
3- the viral genome enters the nucleus and gets
a}- replicated
b} Transcripted- DNA to RNA
4-the RNA, is translated outside the nucleus forming the virions proteins
5-the protein and replicated genome gets assembled to form more virions and is released
how does virus replication occur when using RNA
the RNA is injected into host and an enzyme known as reverse transcriptase, converts the RNA to DNA which can then be used normally in the steps of virus replication
what is the problem of RNA viruses such as HIV?
during the reverse transcription of RNA to DNA, the DNA is not checked for any mistakes, leading to mutations and variations between viruses
describe the lytic cycle{ active }
1- the virus binds to receptor of host cell and injects its viral genetic material into it
2-the viral genetic material takes over the host functions and starts transcribing and replicating its own DNA
3-once all the new materials are made, assembly of the new virion is made
4-due to increase in number of new virion, lysis of the cell occurs to release new viruses
what is the problem of cell lysis?
cells cannot survive without its cell membrane
what happens to other viruses inside the host cell when lysis occurs?
* host cell is multicellular
the virus can either use its own genetic material for replication or the new genetic material to infect other cells
describe the lysogenic cycle[ hidden]
1- virus attaches to the host cell and injects its genetic material
2-the genetic material stays hidden within the genetic material of the host cell
3- the host cell multiplies normally, replicating the viral DNA as well
4-a trigger such as lack of food for host cell or a chemical trigger occurs
5- the trigger causes the viral DNA to separate and go into the lytic cycle
in which cycle of replication can the host cell [in this case a microorganism one] be made more or less pathogenic [ cause disease]
in the lysogenic cycle/ hidden
what are the 5 phases and stages of replication and describe them
1- absorption- virus attachment
2- penetration-injection of genetic material
3- eclipse- starting of virus infection
4- doubling- replication of virus
5-virus exit phase-lysis of cell membrane
what are 4 examples of common viruses
1- influenzas A virus 2- poliovirus 3-bacteriophages 4-HIV 5- hepatitis B virus
what is a cytopathic effect
structural change in host cell caused by viral invasion