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Flashcards in Morphology of Viruses Deck (68)
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1

Smallest Viruses

Porcine Circovirus type-1 (17nm)

Parvovirus (18nm)

2

Largest Viruses

Pandoravirus (400nm)

Poxvirus (200x300nm)

3

Pleomorphism

Ability of some viruses to alter their shape or size

4

Most viruses are _______ or __________ shaped.

Most viruses are rod or spherical shaped.

5

Common methods used to deterime the morphology of viruses:

Electron Microscopy (EM)

Cryo-Electron Microscopy (Cryo-EM)

X-Ray Crystallographic Method

Nuclear Magnetic Resonance (NMR)

6

_____________ method requires negative staining with electron dense material such as Uranyl Acetate or Phosphotungstate.

Electron Microscopy (EM) method requires negative staining with electron dense material such as Uranyl Acetate or Phosphotungstate.

7

Resolution range for electron microscopy

50-75 angstroms

8

________________ method allows the observation of biological specimens in thier native environment (not fixed or stained in any way)

Cryo-Electron Microscopy (Cryo-EM) method allows the observation of biological specimens in thier native environment (not fixed or stained in any way)

9

Resolution range for Cryo-Electron Microscopy

3.3 to 20 angstroms

10

Explain the X-Ray Crystallographic method process

1. Virus or viral protein is crystalized

2. X-ray 

3. Deflection mesasured to form electron density map

4. Protein model created

5. Reconstruction of virus structure

11

Capsid

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

12

The capsid is made up of ______ held together by covalent bonds

The capsid is made up of capsomeres held together by covalent bonds

13

Viruses have one capsid, except for _____________ which have a double layered capsid

Viruses have one capsid, except for Reoviruses which have a double layered capsid

14

Capsomere

Basic subunit protein in the capsid of a virus

15

Nucleocapsid

Capsid + Virus Nucleic Acid/Genome

16

Common capsid symmetries

Helical Symmetry

Cubic/ Icosahedral Symmetry

Complex

17

Incomplete virions cannot form ____________ symmetry.

Incomplete virions cannot form helical symmetry.

18

Helical nucleocapsids of animals are enclosed by ____________

Helical nucleocapsids of animals are enclosed by lipoprotein envelope

19

Naked helical nucleocapsids are common among _______ viruses.

Naked helical nucleocapsids are common among plant viruses.

20

Icosahedral viruses always have ________ corners

Icosahedral viruses always have 12 corners

21

Two types of capsomers present in icosahedral capsid

Pentagonal Capsomers

Hexagonal Capsomers

22

Pentons make up the (vertices/facets)

Pentons make up the (vertices/facets)

23

Hexons make up the (vertices/facets)

Hexons make up the (vertices/facets)​

24

Triangulation Number (T-Number)

Describes the relation between the number of pentagons and hexagons of the icosahedron.

25

The (larger/smaller) the T-Number the more hexagons are present relative to the pentagons.

The (larger/smaller) the T-Number the more hexagons are present relative to the pentagons.

26

T- Number Equation 

T = H+ h * k + k2

27

________ has a T = 1, simplest icosahedron

Parvovirus has a T = 1, simplest icosahedron

28

Functions of viral capsid

1. Structural symmetry

2.  Encase and protect viral nucleic acid 

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

4. Interact with host cell membrane to form envelope

5. Uncoat genome

6. Transport viral genome

7. Recognize and package nucleic acid genome

29

Viral envelope

Lipid bilayer with embedded proteins, facilitates virus entry into host cells and may also help the virus to adapt fast and evade host immune system

30

Explain how a virus acquires its envelope

Acquired by budding of viral nucleocapsid through a cellular membrane