Viruses Flashcards
Which kingdom are viruses found?
They are not in a kingdom
- because they are they do not share all characteristics with living cells.
- they are BETWEEN LIVING AND NONLIVING matter
What is unique about a virus?
Outside the cell it has no life; but inside the cell it can REPRODUCE
List some common viruses.
common cold smallpox cold sores influenza polio mumps
When was the virus discovered?
1934 through electron microscope
viruses are very small, measured in nanometers
What are the parts of a virus?
- inner nucleic acid core -
- CAPSID = outer protective protein coat
- Capsid 95% of the virus and gives its shape
- Occasionally lipid membrane may enclose capsid, as in HIV (AIDS virus)
Is a virus smaller or larger than a bacteria?
Smaller
Where does the lipid layer come from, if a virus has one?
The host cell’s membrane
What type of nucleic acid is in a virus?
contains only one of:
- DNA
- RNA
* may be single strand or double strand
various geometric shapes of viruses
icosahedral - roughly spherical helical - spiral complex (have capsids)
Replication
The process by which genetic material is duplicated
Steps of viral replication
- Attachment and entrance. The virus recognizes host cell and enters (whole virus of just DNA enters)
- Synthesis of protein and nucleic acid (viral DNA or RNA directs the host)
- Assembly. The nucleic acids, proteins and enzymes are brought together as new virus.
- Release of new viruses. Host cell dies.
Viral Replicatin figure
Lytic Cycle
- the replication cycle
- causes the host cell to burst and die
- can take 25-45 minutes
Lysogenic cycle
- Certain viruses, such as cancer viruses
- Cycle does not kill the host outright, might last for years
- Viral DNA becoem part of chromosome and is dormant
- Later the virus will be stimulated to go into the lytic cycle adn decome virulent
Epstein-Barr virus
mononucleosis (DNA)