Lecture 1.1 1/23/24 Flashcards
What determines the size and shape of a virus?
-nucleic acid content
-amount of proteins
-arrangement of proteins
What does virus structure have an impact on?
-cell type(s) the virus can enter
-environment the virus can survive in
-ability for virus to survive outside host
-viral life cycle
What is a virus?
infectious particle that parasitizes off a host cell by using its machinery to produce more viruses
What is a virion?
a complete virus particle outside the host cell consisting of DNA/RNA genome and a protein coat
What is a capsid?
protein shell that encapsidates viral genomic material
What is a nucleocapsid?
viral nucleic acid + capsid
What are capsomeres?
small protein subunits that make up the capsid
What encodes for the capsid proteins?
the viral genome, ALWAYS
Where can attachment proteins for viral entry be found?
on the capsid or on the envelope
What are the three main virus structures?
-icosahedral
-helical
-complex
What is an icosahedral structure?
polyhedral capsids with multiple flat sides forming a rigid shell
What is a helical structure?
wrap of proteins around the nucleic acid strand
What is a complex structure?
structure that is neither entirely helical nor icosahedral, and is often pleomorphic
What is a spherical form?
formation that can arise when helical nucleocapsids are enveloped
What are the two types of icosahedral structure?
-simple
-complex
What is an example of a simple icosahedral virus?
poliovirus
What is an example of a complex icosahedral virus?
adenovirus
What are the characteristics of helical structure?
-simplest arrangement of capsomeres
-lowest free energy
What is an example of a complex virus?
poxvirus
What are naked viruses?
viruses without a lipid envelope
What are enveloped viruses?
viruses with a lipid envelope
How do enveloped viruses acquire their envelope?
-obtained from lipid bilayer in the host cell
-plasma membrane, endosomal membrane, or ER/Golgi membrane
What are glycoproteins?
viral proteins on the envelope that are required for infection
What are the characteristics of naked viruses?
-environmentally stable to temp, acids, proteases, detergents, and drying
-easily transmitted
-can retain infectivity when dried out
-can survive adverse conditions
-resistant to most treatments other than bleach
What is an example of naked viruses?
parvoviruses
What are the characteristics of enveloped viruses?
-environmentally labile to temp, acids, detergents, and drying
-must stay wet in environment
-spread through droplets, secretions, and organ transplants/blood transfusions
-do not survive on external surfaces
-do not survive in GI tract
What is the benefit of a viral envelope?
-allows for increased antigen variability and evasive capacity
-requires host to produce both antibody and cell-mediated immune responses
