Structure & Chemical Composition of Viruses - Lec 2 Flashcards
Rank the viruses from biggest to smallest:
Parvovirus, Pandoravirus, Circovirus (type I), Poxvirus,
Pandoravirus; Poxvirus; Parvovirus; Circovirus (type I)
Which virus is considered filament-shaped ?
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Ebola
What does it mean to be pleomorphic?
the ability of some Virus to alter their shape or size (attributed to the lipid envelope of the virus)
Electron microscope (EM) utilize negative staining to stain the background. What solutions are used to stain the background?
Urinyl acetate or Phosphotungestate
What is the highest resolution an EM can reach ?
50-75 Angostroms
Which one of these statements is false regarding Cryo-Electron Microscopy ?
A. It observes specimens in freezing conditions
B. It can have a resolution of 3.3 -20 Angostroms
C. It can observe specimens in native environments at - 180 degrees Celsius
D. The images are not as detailed
D. The images are not as detailed = False
Images are very detailed; there is a huge improvement in clarity and resolution
What is the function of the X-ray Crystallographic Method?
It utilizes X-rays to bombard the virus which diffract off of the virus and a computer and an electron density map which will then generate a protein modeled structure of the virus.
Note: The nuclear magnetic resonance in the same process but utilizes radiation instead of x-rays
Nonstructural proteins are seen in extracellular virions.
True or False
False
Note: Nonstructural proteins are only seen when the virus is undergoing replication in the host cell. You are unlikely to encounter Nonstructural proteins in an extracellular mature virus of the virion
An incomplete virion is composed of ______
A. Only nucleic acid (DNA/RNA)
B. Only lipid envelope
C. Only capsid
D. Lipid envelope and nuclei acid, no capsid
C. Only capsid
Note: It lacks the nucleic acid
The family of a virus is denoted by suffix _______
A. Virales
B. Virinae
C. Virus
D. Viridae
D. Viridae
Which one of the following is NOT a component of a virus ?
A. Nucleic acid
B. Capsid
C. Envelope
D. Capsule
D. Capsule
The viral matrix protein is located between the viral nucleic acid (DNA/RNA) and the capsid.
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True or False?
False
Note: The viral matrix protein is located between the viral envelope and the capsid. It offers stability to the virus envelope.
Which one of the following is NOT a mechanism of genetic diversity of viruses ?
A. Reassortment
B. Point mutations
C. Recombination
D. Conjugation
D. Conjugation
The Tobacco Mosaic Virus is…
A. Filament-shaped
B. Rod-shaped
C. Brick-shaped
D. Bullet-shaped
B. Rod-shaped
Correctly arrange the steps X-ray Crystallographic Method in order to determine the morphology of the virus…
1. Bombard with x-rays X-rays will be reflected
- Fed into a computer
- Using software you can reconstruct the virus structure
- Crystallize the virus
- Measure the angle/intensity of inflection
4 -> 1 -> 5 -> 2 -> 3
- Crystallize the virus
1. Bombard with x-rays (X-rays will be reflected ) - Measure the angle/intensity of inflection
- Fed into a computer
- Using software you can reconstruct the virus structure
Which method results in the outcome of an even more detailed morphological structure of the virus?
A. Cryo-Electron Microscopy
B. X-ray Crystallography
B. X-ray Crystallography
What common method used to determine the morphology of viruses is very similar to X-ray Crystallography but instead uses electromagnetic radiation ?
Nuclear Magnetic Resonance (NMR)
Arrange the layers of a virus from outermost to inner most
Capsid
Nucleic acid
Envelope
Envelope -> Capsid -> Nucleic acid
A _______ is the protein shell of a Virus that encases/envelopes the viral nucleic acid or genome.
Capsid
A capsid is made up of capsomeres held together by …
A. Covalent bonds
B. Non-covalent bonds
C. Ionic bonds
D. Hydrogen bonds
B. Non-covalent bonds
A ________ is the basic subunit protein in the capsid of a virus.
Capsomere
Most Viruses have one capsid, except Reoviruses which have a double layered capsid.
True or False ?
True
Capsid + Virus Nucleic acid (DNA or RNA)/Genome
A. Nucelosome
B. Nucleocapsid
C. Capsomere
D. Nucleovirus
B. Nucleocapsid
Animal viruses with helical capsid ARE
A. Enclosed in an envelope
B. Naked
A. Enclosed in an envelope
In all Animal Viruses, the Helical Nucleocapsid is enclosed within a Lipoprotein Envelope.
True or False?
True
Naked Helical Nucleocapsids are common among Animal Viruses, eg. Tobacco Mosaic Virus
True or False ?
False
Note: They are common among plant viruses
An Icosahedron is a solid with
A. 12 corners [vertices], 20 facets [Equilateral triangular faces], and 30 edges
B. 18 corners [vertices], 20 facets [Equilateral triangular faces], and 32 edges
C. 10 corners [vertices], 30 facets [Equilateral triangular faces], and 20 edges
D. 18 corners [vertices], 30 facets [Equilateral triangular faces], and 30 edges
A. 12 corners [vertices], 20 facets [Equilateral triangular faces], and 30 edges
Two types of capsomers are present in the icosahedral capsid. They are the hexagonal capsomers at the vertices (hexons) and the pentagonal capsomers making up the facets (pentons).
True or False?
False
Note: Two types of capsomers are present in the icosahedral capsid. They are the pentagonal capsomers at the vertices (pentons) and the hexagonal capsomers making up the facets (hexons).
The Triangulation number (T-number) describes the relation between the number of pentagons and hexagons of the icosahedron. The larger the T-number the more hexagons are present relative to the pentagons. Triangulation number is calculated using the formula:
A. T=h^2 + hk + k^2
B. T=h + hk + k^2
C. T=h^2 + hk + k
T=h^2 + 2(hk) + k^2
A. T=h^2 + h*k + k^2
Note: Where h and k are the distances between the successive pentagons on the virus surface for each axis.
Simply remember, h and K are calculated based on the number of jumps from one pentagon to adjacent pentagon across the hexamer.
Which virus has the simplest icosahedron, with a T=1 value and a capsid consisting of 60 copies of CP protein ?
A. Reoviridae virus
B. Poxvirus
C. Parvovirus
D. Bacteriophage
C. Parvovirus
Reoviridae, The outer capsid has a T=13 icosahedral symmetry, the inner capsid a T=2 icosahedral symmetry. All of the following belong to the reovirus family EXCEPT ?
A. Cypovirus
B. Circovirus
C. Orthoreovirus
D. Rotavirus
B. Circovirus
This viral envelope glycoprotein helps the virus fuse with host cytoplasmic membrane, thereby allowing penetration of genome into cell ___________.
Fusion protein
