Viral Structure, Classification & Replication Flashcards
Viruses Introduction
Human viral pathogens are classified on the basis of virion structure, characteristics of the nucleic acid, and replication strategy
The infectious virus particle is called a virion
Virions contain nucleic acid genetic material surrounded by a protein coat (capsid); some viruses also have a lipid and glycoprotein envelope
A delivery system that surrounds a payload
Have to multiply to cause disease; don’t produce toxins (unlike some bacteria).
Genomes.
Genomes can be either DNA or RNA and single-stranded or double-stranded
Single-stranded RNA genomes can have the same (+) or complimentary (-) polarity as viral m-RNA. Positive can be replicated right away. - need to be retrotranscribed first.
Genomes may be linear or circular; some linear RNA genomes are segmented
Viral genomes are haploid except for retroviruses which are diploid
The capsid and genome of enveloped viruses is called a nucleocapsid
Capsids or nucleocapsids are composed of many copies of one or very few viral-encoated protein subunits
Capsids have either a cylindrical shape (helical form) or a cubic shape (icosahedron form)
Capsids function in packaging of the nucleic acid in viral assembly and protection of the nucleic acid
Capsids of naked viruses contain the viral attachment protein (VAP)
IF BODY MAKES ANTIBODIES FOR VIRUSES ATTACHMENT PROTEINS, VIRUS CAN’T ENTER
CAPSOMERE ARRANGEMENT
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ENVELOPED HELICAL Nucleocapsid
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ENVELOPE
*Composed of lipids, proteins and glycoproteins
*Specific glycoproteins act as VAPs for enveloped viruses
*Acquired from viral-modified cellular membranes during egress of virus from host cell
*Is disrupted in non-moist environments or by heat, acid and lipid solvents
- Proteins inputted into membrane required for attachment. Disrupt these proteins and remove viron ability to enter host.*
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PEPLOMER (GLYCOPROTEIN)
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