chapter 5: viruses and prions Flashcards
(26 cards)
What are some traits of a VIRUS?
- Acellular with a protein coat and nucleic acid genome
- Lacks independent metabolism
- Needs host cell
- Few/no enzymes
- Cannot synthesize proteins
Viruses are known as ___
Filterable
Bacteriophage
A virus that infects a bacteria
Size comparison of Viruses (Yeast) vs. Bacteria
- Small to large
- Long
- Narrow
What are some traits of a VIRAL STRUCTURE?
- Protein coat (capsid)
- Nucleocapsid - simplest form of a capsid
- Naked - a virus w/o and enevelope
- Virion - fully formed virus that can infect
- Envelope - nucleocapsid outside layer
Which envelope proteins are involved in virus assembly?
Membrane protein (M) and Envelope protein (E)
Which envelope protein mediated virus entry into host cells?
Spike proteins (S)
What are SPIKES (peplomers)?
Proteins on outer surfaces that project externally
What is a VIRAL CAPSID made of?
Capsomeres - identical protein subunits
What are traits of a HELICAL CAPSID?
- Helix shaped
- Rigid, flexible
- Genome filament
- Length is long enough to cover genome
What are traits of a ICOSAHEDRAL CAPSID?
- Variations in the # of capsomeres
- Some have spikes
- Variety in shape
What are traits of a COMPLEX CAPSID?
- Elaborate structure found in bacteriophages
- Not symmetrical
- No envelopes
What are traits of a VIRAL GENOME?
- 4 types: DS DNA, SS DNA, DS RNA, SS RNA
- Genome can be circular or linear
What are the phases of ANIMAL VIRAL REPLICATION?
- Absorption
- Penetration and un-coating
- Synthesis
- Assembly
- Release
How do viruses ATTACH or ABSORB?
Attach via spikes or capsid –> receptors on host cell surface
How do viruses PENETRATE or UN-COATING?
Entire virus/genome enters host
How do viruses REPLICATE?
- Genome transcribed and translated
- Synthesizes building blocks for new viruses once inside host
- DNA viruses enter host cells’ nucleus and replicate
DNA virus process
DNA has info -> Replicates -> mRNA made -> mRNA decoded and proteins
How do viruses REPLICATE? (positive)
- RNA replicates and assembled in cytoplasm
- Carry in proteins to complete synthesis
- ssRNA is translated into viral proteins
How do viruses REPLICATE? (negative)
- ssRNA cannot serve as mRNA to form viral proteins, uses
– ssRNA as
template for +ssRNA - New + strand intermediates synthesized
- Newly synthesized + strand serves as template for more -ssRNA
synthesis & mRNA
How do viruses REPLICATE? (dsRNA)
- dsRNA as a template for mRNA
- Virus transcribed dsRNA –> +ss RNA
How do viruses ASSEMBLE?
Construction from various viral parts
How do viruses RELEASE?
- Via host cell lysis
- Non-enveloped viruses and phages
- Lysozyme attacks PG in host and releases virus
- Protein (holin) creates holes in cytoplasmic membrane
- Lysozyme acceses cell wall
How do viruses RELEASE?
- Via host cell lysis
- Non-enveloped viruses and phages
- Lysozyme attacks PG in host and releases virus
- Protein (holin) creates holes in cytoplasmic membrane
- Lysozyme acceses cell wall
