Lecture 9 Flashcards
What is a virus?
An acellular particle that infects hosts
Needs a host to multiply
Disrupts normal host cell function
Has no membrane
Only DNA or RNA
Protein capsid
Little personal enzymes
What type of hosts do viruses infect?
Animals
Plants
Fungi
Protozoa
Bacteria
Specific host type for virus
Familiar trait (spikes)
What are the structures of viruses?
Nucleic acids
Capsid
Envelope
Virus morphology
What are the characteristics of nucleic acids in viuses?
DNA or RNA
Single or double stranded
Linear or circular or segmented
Very few nucleic acids compared to independent bacteria because they depend on host to provide recipes the virus does not have
What are the characteristics of capsid?
It is a protein coat made of capsomeres around nucleic acid
Arrangement is specific to virus
Nucleic acids + capsid = Nucleocapsid
Spikes attach to capsid
No capsid means virus is naked and spikes attach to nucleic acid
What are the characteristics of envelopes?
Not in all viruses
Is a lipid bilayer (not plasma) sacrificed from host cell
Goes around nucleocapsid
Spikes on outside to get into host cell
What are the different morphology of viruses?
Helical virus - long rods. Ridgid and flexible
Polyhedral virus - icosahedral (20 triangle faces) or others
Enveloped virus - spherical a dictated by the lipid bilayer
Why are complex viruses complex?
Complicated structure
Added protein attachments
Most common in bacteriophages which are viruses that infect bacteria
What is the classification of viruses based on?
Nucleic acid type
Capsid structure - polyhedral, helical
Envelope presence - naked or enveloped
How are viruses named?
Family - end with viridiae
Genus - ends with virus
Species - descriptive name
What are the 6 types of multiplication of animal viruses?
Absorption
Penetration
Uncoating
Biosynthesis
Maturation and assembly
Releases
What are the characteristics of adsorption in multiplication?
Attaching to host via attachment sites composed of proteins or glycoproteins for host recognition
What are the characteristics of penetration in multiplication of animal viruses?
Entry into host cell via endocytosis
(Naked virus) or fusion (enveloped virus must be the same membrane)
Naked cells will kill host cell
Envelope will take over host cell
What are the characteristics of uncoating multiplication?
Separation of viral nucleic acid from capsid
What are the characteristics of biosynthesis multiplication?
Takes over host metabolic enzymes
DNA virus - inserts into nucleus to be replicated
RNA virus - inserts into cytoplasm to be replicated
Viral proteins synthesized in cytoplasm aka capsomere construction
What are the characteristics of maturation and assembly multiplication?
New virus are assembled from nucleic acids and capsomeres
Nucleocapsid are formed
What are the characteristics of release in multiplication?
Naked virus bursts out of host killing it
Enveloped virus buds out of the host cell taking some membrane leaving the host cell alive
What are the types of infections?
Acute
Persistent
What are the characteristics of acute infections?
Short
Disease results from tissue damage
Lysis of host cells to infect more cells
Gradually eliminated (days or months)
Host may develop lasting immunity
What are the characteristics of persistent viral infections?
Virus is always present in body
May cause disease from persistent infection
Can be no symptoms
Host can cause transmit to others
4 categories
- Acute infection with complication
- Chronic infection
- Slow infection
- Latent infection
What are the characteristics of acute infection with complication?
After acute infection period still active virus particles
Gradual increase of virus particles over years
Virus can cause serious disease years later
What are the characteristics of chronic infections?
Infectious virus is present at all times. Kinda high but not
Disease may or may not be present
Acute leads to chronic
Ex. Herpes
What are the characteristics of slow viral infections?
Virus increases over a very long period of time followed after initial infection. Aka asymptomatic period (feel fine)
Slow progressive disease results
Ex. HIV
What are the characteristics of latent viral infections?
Reactivated after asymptomatic period
Symptoms can be different when reactivation occurs
Ex. Chicken pox to shingles
