Structure & Chemical Composition of Viruses

Question 1

What is the smallest virus?

Answer 1

Porcine circovirus type 1

Question 2

What is the largest virus?

Answer 2

Poxvirus

Question 3

What shape is the ebola virus?

Answer 3

Filament-shaped

Question 4

What shape is the rabies virus?

Answer 4

Bullet-shaped

Question 5

What shape is the bacteriophage?

Answer 5

Tadpole-shaped

Question 6

What shape is the tobacco mosaic virus?

Answer 6

Rod-shaped

Question 7

What shape is the poxvirus?

Answer 7

Brick-shaped

Question 8

What shape is the rotavirus?

Answer 8

Spherical

Question 9

What is pleomorphism?

Answer 9

Ability of some viruses to alter their shape or size?

Question 10

What are 4 common methods to determine the morphology of viruses?

Answer 10

1. Electron microscopy (EM)
2. Cyro-electron microscopy (Cryo-EM)
3. X-ray crystallographic method
4. Nuclear magnetic resonance (NMR)

Question 11

What are 4 important characteristics of virus morphology?

Answer 11

1. DNA or RNA genes
2. Capsid
3. Envelope, a bubble of fat
4. Molecules of protein

Question 12

What is a capsid?

Answer 12

Protein shell of a virus that encases/envelopes viral nucleic acid or genome

Basic subunit protein in virus capsid

Question 13

What is a capsid made of?

Answer 13

Capsomeres

Question 14

Most viruses have one capsid, except?

Answer 14

Reoviruses

Question 15

What makes up a nucleocapsid?

Answer 15

Capsid + Virus Nucleic acid/Genome

Question 16

In all animal viruses, the helical nucleocapsid is enclosed with what kind of envelope?

Answer 16

Lipoprotein envelope

Question 17

What kind of nucleocapsid does a plant virus have?

Answer 17

Naked helical nucleocapsid

Question 18

What two types of capsomeres are present in a icosahedral capsid?

Answer 18

1. Pentagonal capsomeres (pentons)/(always 12 pentons

2. Hexagonal capsomeres (hexons)

Question 19

What is the triangulation number (T-number)

Answer 19

T = h2 + h * k + k2

Relationship between penton (constant) and Hexon (variable)

Question 20

What are two types of icosahedrals?

Answer 20

1. Naked

2. Enveloped

Question 21

What is the simplest icosahedron? (T=1)

Answer 21

Parvovirus (capsid consists of 60 copies of CP protein)

Question 22

What kind of Icosahedral symmetry does Reoviridae have?

Answer 22

Outer capsid has T=13, inner capsid has T=2

Question 23

What kind of symmetry does poxvirus have?

Answer 23

Complex symmetry

Question 24

T/F: A viral capsid is responsible for structural symmetry of virus particle

Answer 24

True

Question 25

What is the importance of receptor attachment proteins on viral capsid?

Answer 25

Facilitate the attachment of virus to specific receptors on susceptible host cells

Question 26

The viral capsid interacts with host cell membrane to form the ___________

Answer 26

Envelope

Question 27

What is responsible of uncoating the genome in host cell?

Answer 27

The viral capsid

Question 28

The viral capsid transports the which genome to the appropriate site

Answer 28

Viral genome

Question 29

The viral capsid facilitates __________ of nucleic acid genome

Answer 29

Packaging

Question 30

The viral capsid contains antigenic sites that determine the __________ of the virus

Answer 30

Antigenicity

Question 31

What is the envelope of an enveloped virus made of?

Answer 31

Lipid bilayer with embedded proteins

Question 32

How does a virus acquire the envelope?

Answer 32

Via budding of viral nucleocapsid through a cellular membrane such as cytoplasmic membrane, golgi membrane or nucleus membrane

Question 33

What are the two proteins primarily found in virus envelope?

Answer 33

1. Glycoprotein | 2. Matrix protein

Question 34

What are the two types of glycoproteins in virus envelope?

Answer 34

1. External glycoprotein | 2. Channel proteins

Question 35

The external glycoproteins are the major (Antigens or antibodies?) of the virus

Answer 35

Antigens

Question 36

What are the functions of external glycoproteins?

Answer 36

Hemagglutination, receptor binding, antigenicity, and membrane fusion

Question 37

What are channel proteins?

Answer 37

Mostly hydrophobic proteins that form a protein lined channel

Question 38

What is an important virus envelope glycoprotein?

Answer 38

Fusion (F)

Question 39

What are the important functions of a virus envelope matrix protein?

Answer 39

1. Role in virus assembly 2. Stabilization of lipid envelope 3. Recognition site of nucleocapsid 4. Mediates encapsidation of RNA-nucleoprotein cores in to membrane envelope

Question 40

How is the lipid bi-layer in virus envelope acquired?

Answer 40

Acquired from a cellular membrane of host cell, such as nuclear membrane, ER membrane, etc.

Question 41

How is the lipid bi-layer in virus envelope maintained?

Answer 41

In aqueous or moist environment

Question 42

T/F: Enveloped viruses are easier to sterilize than non-enveloped viruses and cannot survive for longer periods in environment

Answer 42

True

Question 43

Where is the matrix protein located?

Answer 43

Between capsid and envelope

Question 44

What is antigenic drift?

Answer 44

Change in antigenicity of virus due to genetic drift

Question 45

What is antigenic shift?

Answer 45

Recombination Exchange of nucleotide sequences between different, but usually closely related viruses during replication

Question 46

What is the most important mechanism for high genetic diversity in viruses with segmented genomes?

Answer 46

Reassortment (antigenic shift)

Question 47

What are 4 important viral enzymes critical to viral infection?

Answer 47

1. Lysins 2. Retroviral integrase (IN) 3. Reverse transcriptase (RT) 4. Nucleic acid polymerases

Question 48

What 3 different roles do viral nonstructural proteins do?

Answer 48

1. Play role within infected cell during virus replication 2. Act in regulation of virus replication 3. Act in regulation of virus assembly

Question 49

T/F: Nonstructural proteins are seen in extracellular virions

Answer 49

False

Question 50

Incomplete virions are virions without _______ ______

Answer 50

Nucleic acid (empty capsid)

Question 51

What is a defective virion?

Answer 51

Lacks full complement/copy of viral genes, resulted from mutations or errors

Question 52

What is a pseudovirion?

Answer 52

Contains non-viral genome within viral capsid

Question 53

What are pseudotypes?

Answer 53

When related virus infect same cell, the genome of one virus may be enclosed in heterologous capsid of second virus