viruses Flashcards
General information
- microscopic
- pathogenic
consist of: - genetic material (DNA/RNA)
- capsid (protein coating around genetic mat)
- envelope (has protein markers on it- not all have this)
Virus reproduction (how + steps)
viruses invade a host cell and use the cells machinery to reproduce themselves
3 step of viral infection:
- attachment & penetration
- viral genome expression and replication
- assembly and release of new viruses
- Attachment & Penetration
viral attachment:
virus attaches to + enters the host cell
- the virus has specific “keys” to “unlock” specific types of cells
(viruses are specific to their hosts)
how are viruses specific to their host
1) protein on the viral envelope signal specific types of cells to let them in
2) protein match their hosts cells like a lock & key
three ways the virus can enter the cell
a) punch a hole into the cell and inject their DNA
b) fuse their envelope with the cell membrane, allowing DNA inside
c) become phagocytosed (engulfed) by the host cell
phagocytosis
when one cell engulfs another cell of virus whole
bacteriophage
- also called “phage”
- a virus that infects bacteria
name the two types of viral life cycles and characteristics
1) Lytic cycle: shorter-term illness
2) Lysogenic cycle: long-term, dormant viruses
lytic cycle (simple explanation)
the host cell is used to replicate the virus and then the host cell is killed
lytic cycle steps (5)
1) attachment: specific receptor proteins on viral envelope match virus to the host cell
2) penetration: viral genome is inserted into the host cell
3) biosynthesis: host cell machinery is used to copy, transcribe and translate viral genome, which encodes the building materials for new viruses and the viral assembly proteins
4) assembly: new viruses are put together
5) release: new viruses break open (kill=lyse) host cell, and new viruses are released to infect other cells
lysogenic cycle (simple explanation)
viral genome is incorporated into the hosts genome
lysogenic cycle steps (3)
1) virus attaches and genome enters host cell
2) viral DNA is inserted into hosts DNA
3) prophage is replicated when host cell replicates ( eventually prophage DNA leaves host DNA and enters lytic cycle)
what is prophage
integrated genome
dormant lysogenic infections
- during the lysogenic replication process, the virus appears dormant because the host does not get sick
- when the virus exits the lysogenic cycle, many cells are already infected therefore progression of the disease is much faster
examples of lysogenic cycle human viral infections (4)
- Herpes simplex (herpes, cold sores)
- Varicella Zoster Virus (shingles)
- Human Papilloma Virus (Warts)
- Human Immunodeficiency Virus (HIV) (AIDS)