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sem 3: viro > Structural and Chemical Composition of Viruses - Ghosh > Flashcards

Structural and Chemical Composition of Viruses - Ghosh Flashcards

1
Q

What is the smallest virus?

A

Porcine circovirus type 1

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2
Q

What is the largest virus?

A

Poxvirus in animals, humans and birds

200nm diameter
300 nm length

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3
Q

What shape is the rabies virus?

A

Bullet-shaped

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4
Q

What shape is ebola virus?

A

Filament shaped

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5
Q

What shape is the tobacco mosaic virus?

A

Rod shaped

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6
Q

What shape is pox virus?

A

Brick shaped

** largest virus

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7
Q

What shape is rota virus?

A

Spherical

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8
Q

What shape is a bacteriophage?

A

Tadpole- shaped

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9
Q

___________ is the ability of some viruses to alter their shape or size

A

Pleomorphism

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10
Q

What common methods are used to visualize and determine morphology of a virus?

A
  1. Electron microscopy
  2. Cryo-Electron microscopy
  3. X-ray Crystallographic method
  4. Nuclear Magnetic Resonance (NMR)
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11
Q

What is a capsid?

A

protein shell of a virus that encases the viral nucleic acid or genome

made of capsomeres

*** most viruses have 1 capsid EXECPT Reoviruses which have a double capsid

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12
Q

________ is the basic subunit protein in the capsid of a virus

A

Capsomere

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13
Q

What makes up a nucleocapsid?

A

Capsid + nucleic acid (RNA or DNA)/genome

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14
Q

Which virus has a double layered capsid?

A

Reoviruses

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15
Q

What is the formula to calculate the triangulation number?

A

T = h2 + h×k + k2

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16
Q

In all animal viruses, the helical nucleocapsid is enclosed within a __________

A

Lipoprotein envelope

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17
Q

Naked helical nucleocapsids are common among _________-

A

Plant viruses

Ex: tobacco mosaic virus

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18
Q

What does the T number describe?

A

The relation between the # of pentagons and hexagons of the icosahedron

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19
Q

Describe the capsid symmetry and virus architecture of parvovirus

A

T=1

** simplest icosahedron

20
Q

Describe the capsid symmetry and virus architecture of reoviridae

A

Outer capsid has a T=13 icosahedral symmetry

Inner capsid has a T=2 icosahedral symmetry

21
Q

Give an example of a virus with a complex capsid symmetry and virus architecture

A

Poxvirus

** also bacteriophage but its not a virus

22
Q

What is the function of the viral capsid?

A
  1. Structural symmetry of virus particle
  2. Encases + protects viral nucleic acid from enzymes, chemicals, pH, temp
  3. Receptor attachment proteins on capsid helps attach virus to host cells
  4. Determines antigenicity of virus
23
Q

What is the envelope made of?

A

Lipid bilayer with embedded proteins

24
Q

How is the viral envelope acquired?

A

By budding of nucleocapsid through cytoplasmic membrane, golgi membrane, or nucleus membrane

25
Q

What viral proteins are found in the envelope?

A
  1. Glycoproteins (External glycoprotein and channel protein)
  2. Matrix protein
26
Q

Describe the external glycoprotein found in the viral envelope

A
  • Major antigens of the virus involved in
  1. Hemagglutination
  2. receptor binding
  3. antigenicity
  4. membrane fusion
27
Q

Describe channel proteins found in the viral envelope

A

** mostly hydrophobic proteins that form a channel through the envelope

  • alters permeability of membrane
    -modifies internal enviro of the virus
28
Q

Describe the matrix protein found in the viral envelope

A

*** IMPT for budding

  • Links internal nucleocapsid to lipid membrane envelope
  • Plays a role in viral assembly

-Stabilizes lipid envelope

29
Q

Which survives longer: a non-enveloped virus or an enveloped virus?

A

Non enveloped virus survives longer.

Enveloped viruses are easy to sterilize + dont survive long

30
Q

Which solvents can inactivate an enveloped virus?

A
  1. Ether
  2. Chloroform
  3. Sodium deoxycholate, detergents, etc
31
Q

True or false: The viral matrix protein is located between the viral nucleic acid (DNA/RNA) and the capsid

A

FALSE. Matrix is between envelope and capsid

32
Q

What causes antigenic drift in viruses?

A

Mutations

33
Q

What causes antigenic shift in viruses?

A

Recombination or reassortment

34
Q

What is recombination?

A

Involves exchange of nucleotide sequences between different but closely related viruses during replication

** occurs in a single gene segment

Ex: You have a blue shirt and a red shirt and combine them to make 1 red and blue striped shirt

*** = antigenic shift

35
Q

What is reassortment?

A

MOST IMPT mechanism for genetic diversity of viruses with SEGMENTED GENOME

*** = antigenic shift

** only in viruses with segmented genome/ more than 1 gene segment

36
Q

What are important viral enzymes that are critical to infection?

A
  1. Lysins
  2. Retroviral integrase
  3. Reverse transcriptase
  4. Nucleic acid polymerases
37
Q

What are lysins?

A

Hydrolytic enzymes produced by bacteriophages to cleave host cell wall

38
Q

What are retroviral integrases?

A

Enzymes made by REOVIRUSES (Ex: HIV) that allows genetic material to be integrated into the DNA of the infected cell

39
Q

What is reverse transcriptase?

A

Enzyme used to generate complementary DNA (cDNA) from RNA template

40
Q

What are nucleic acid polymerases?

A

IMPT for viral replication

41
Q

What is the function of viral nonstructural proteins?

A

Plays a role within infected cells during virus REPLICATION

Acts in regulation of virus replication or virus assembly

42
Q

Non structural proteins are seen in extracellular virions

A

FALSE

43
Q

What is an incomplete virion?

A

Lacks nucleic acid , empty capsid

** like a hollow egg shell with no egg inside

** Only contains capsid! no nucleic acid

44
Q

What is a defective virion?

A

Virus that cant replicate bc it lacks a full copy of viral genes

Results from mutations or errors in assembly of virions

45
Q

What is a pseudovirion?

A

Contains non viral genome within the viral capsid

Ex: host nucleic acid instead of viral nucleic acid

46
Q

Define a pseudotype

A

When related viruses infect the same cell, the genome of 1 virus may be enclosed in the heterologous capsid of the 2nd virus

sem 3: viro (17 decks)

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