Microbiology Exam Guide 2
Viruses and Virology
Viruses
o Virus-small infection agent, replicates only in living cells (hosts)
Can only infect specific hosts
Highly specific
Can infect all types of cells
...
Microbiology Exam Guide 2
Viruses and Virology
Viruses
o Virus-small infection agent, replicates only in living cells (hosts)
Can only infect specific hosts
Highly specific
Can infect all types of cells
Some can infect other viruses
o Virion-virus particle that is an extracellular form
Outside the cell
Has nucleic acid genome, surrounded by protein coat
Might have an extra lipid layer, has lots of receptors on the outside
Able to infect
Morphology of Virion
o Smaller than bacteria
o Only have nucleic acids with a protein
coat/capsid
o Icosahedral viruses-spherical
20-300 nm
Symmetry
Form a closed shell
Might have sharp visible edges
Can be enveloped viruses-have a membrane that surrounds the nucleocapsid
Lipid bilayer with embedded proteins or lipid monolayer
Envelope makes initial contact with the host cell
o Helical viruses-tube/rod like
Capsid proteins on outside with RNA in cylindrical shape
Length depends on the length of the nucleic acid
Width is determined by size of packaging or protein subunits (capsomeres)
o Complex viruses-bacteriophages
Have a head, tail, and collar (connects head and tail)
DNA only in the head, rest is protein
Tail helps inject DNA into other cells
o Capsid-protein shell that surrounds the genome of a virus
Made of protein molecules arranged in a highly repetitive pattern around the nucleic acid
Capsomere-subunit of capsid
Smallest morphological unit, can see with electron microscope
Nucleocapsid-complex of nucleic acid and protein packed into the virion
[Show More]