Viruses are not __. They are __. They are very small __ (__) particles.
They are __, meaning they ust do what in order to reproduce.
cells; acellular
infectious (replicating)
obligate, intracellular parasites
infect a host cell and take over that cell's metabolism
What is the capsid?
the protein coat around nucleic acid
Viral envelopes are derived from __.
host cell's membrane
Polio virus only infects __.
primate cells
Variola (smallpox) virus only infects __.
human cells
Plant viruses only infect __.
plant cells
What are the three steps in virus replication.
attachment
penetration (entry)
uncoating
Virus attachment is dependent on what?
specific receptors on the surface of the host cell
What viruses use the lytic/ lysogenic cycle?
phages
What are the steps of lytic reproduction?
attachment
entry of phage DNA (penetration) and degradation of host DNA
Synthesis of viral genomes and proteins
Self-assembly
Release (lysis)
What is different about phages that animal viruses do not do?
Unlike animal viruses that attach, penetrate, and then uncoat, phages' penetration IS their uncoating. They attach and uncoat as they penetrate. Their nucleic acid penetrates into the cytoplasm, but their capsid does not.
Prophage=?
provirus= viral DNA incorporated into cellular DNA
What are the steps to the lysogenic cycle?
Attachment
Penetration (uncoating)
Integration
Replication
True or False:
In the lysogenic cycle, the host bacterium becomes unhealthy and dies.
FALSE
In the lysogenic cycle, the host bacterium remains healthy and reproduces.
What causes a switch from the lysogenic to the lytic cycle?
environmental signal
Phages that use both the lytic and lysogenic cycle are called __.
temperate phages
Viroids infect what?
plants
Prions infect what?
animals
Explain viroids.
infectious
no protein
just nucleic acid
pathogen
affect plant growth
Explain prions.
reproduce, multiply, and infect other organisms
cause brain diseases in mammals
the viral envelope has __
glycoprotein spikes
What gives a virus its shape?
protein coat
What changes shape to fit the other, the virus or the receptor?
