Viruses Flashcards
What is a virus?
Minuscule, acellular infectious agent having either DNA or RNA
What is the cause of most of the diseases that plague the industrialized world?
Viruses
When the virus exists in an extracellular state, what is it called?
Virion
What is the name of the virus’s protein coat that surrounds the nucleic acid core?
Capsid
The capsid together with the nucleic acid core is called what?
Nucleocapsid
What is the outer structure of the virus that encloses the nucleocapsids of some other viruses?
Phospholipid envelope
What is the purpose of the phospholipid envelope of viruses?
Provide protection for viral nucleic acid and means of attachment to host cells
Once in the intracellular state, what happens to the virus structure?
Uncoating occurs and the capsid is removed leaving the virus to exist simply as nucleic acid
What kind of virus only infects a particular kind of cell in a particular host? (Ex. = HIV infecting helper T cells)
Specific
What kind of virus can infect many kinds of cells in many different hosts?
Generalists
What types of organisms are susceptible to some sort of viral attack?
ALL types (even other viruses!)
What virus is a classic example of a “bullet-shaped” virus?
Rabies
What is the most common viral shape?
Icosahedron (20 sided dome)
What is the shape of a polyhedral virus?
Geodesic dome
What is the shape of a helical virus?
Spiral
What is the shape of a complex virus?
Capsids of many shapes
What is a bacteriophage?
A virus that attacks bacteria
How is the viral envelope of a virus obtained?
Acquired from host cell during viral replication or release
What are the viral glycoproteins that project on the viral envelope called?
Spikes
What is the purpose of the viral envelope?
Provides protection, plays role in host recognition, and helps viruses enter host cells
What is lytic replication?
Replication cycle usually resulting in death and lysis of host cell
What is lysogeny?
Modified replication cycle where infected host cells grow and reproduce normally for generations before they lyse
What are the inactive phages called during lysogeny?
Prophages
What is lysogenic conversion?
When phages carry genes that alter the phenotype of a bacterium that can change it from being harmless to a pathogen
Why is viral replication different in animal cells?
Presence of envelope, eukaryotic nature of cells, and lack of cell wall
Replication of animal viruses is guided by what?
Chemical attraction
What are the attachment molecules that mediate attachment for animal viruses?
Glycoprotein spikes
What are the three mechanisms of entry of animal viruses?
Direct penetration, membrane fusion, and endocytosis
What are latent viruses or proviruses?
Animal viruses that remain dormant in host cells
What is the inexpensive way to culture viruses in the laboratory?
In embryonated chicken eggs
What is a prion?
Proteinaceous infectious agent that lacks nucleic acid
Where is cellular PrP protein found, and what does it look like?
Made by all mammals and is a normal structure with alpha-helices
What is a prion PrP?
Disease-causing form with beta-sheets
How can prions be destroyed?
Incineration or autoclaving in sodium hydroxide
What does prion PrP do to cellular PrP?
Converts it into prion PrP by inducing conformational change
In what body system is prion expression most predominant?
Nervous system (possible elsewhere, however)
What are prion diseases in the nervous system?
Formation of large vacuoles in the brain that are characteristically spongy in appearance
What are examples of spongiform encephalopathies?
BSE, vCJD, Kuru
Prions composed of different proteins may lie behind what other muscular and neuronal degenerative diseases?
Alzheimer’s disease, Parkinson’s disease, and ALS
