Viruses

Question 1

percentage of infectious diseases that are from virus

Answer 1

60 %

Question 2

viral infections cause or contribute to what percentage of human cancers

Answer 2

20%

Question 3

are viruses microorganims

Answer 3

no they need host to survive - obligate intracellular

Question 4

genomic material of virus

Answer 4

DNA or RNA but not BOTH

Question 5

what viruses have both DNA and RNA

Answer 5

giant virus aka giruses

Question 6

what is the core of virus

Answer 6

nucleic acid and protein coat

Question 7

what is a virion and another name for it

Answer 7

completely infectious particle

viable virus

Question 8

some properties of viruses

Answer 8

diversity is enormous
limited host range (usually only one cell type)
cell tropism
survival dilemma

Question 9

what does virus having cell tropism mean

Answer 9

they will only infect certain types of cell

Question 10

typical size of virus

Answer 10

typically 0.2 micrometers

Question 11

what do you call viruses/virion that do not have an envelope

Answer 11

they are described as being naked

Question 12

what is the capsid of virions made of and its importance

Answer 12

protein coat

protection

Question 13

protein shell around nucleic acid is called

Answer 13

nucleocapsid

Question 14

what do viruses need to make their proteins aggregate into a capsomer

Answer 14

nothing — self assembly

they do not need energy

Question 15

two main types of capsid symmetry

Answer 15

helical
icosahedral (perfectly stable structure)

Question 16

most animal viruses and most viruses that cause diseases in human have what type of capsid

Answer 16

icosahedral

Question 17

what do all human viruses with a helical capsid have

Answer 17

an envelope

Question 18

describe the structure of a helical capsid

Answer 18

rigid or flexible
length controlled by NA

PS it goes NA –> capsomer (subunit of capsid) –> capsid

Question 19

describe the structure of a icosahedral capsid

Answer 19

20 facets (each an equilateral triangle)
12 vertices
because of the axes has 5:3:2 symmetry

Question 20

what are the two different types of capsomers for icosahedrals

Answer 20

pentons - are at the points of the triangles aka vertices

hexons - make up the face of the equilateral triangle aka the facets

Question 21

since all icosahedral capsids have 20 facets and 12 vertices, where does the size differential come from?

Answer 21

increasing the size of the hexons increases the size of the icosahedral capsid

Question 22

what is the viral envelope composed of

Answer 22

2 lipid layers interspersed with protein molecules

Question 23

virus does not have any lipid so where does it gets the lipid for its envelope

Answer 23

host

Question 24

so where does the material for the viral envelope come from

Answer 24

host (lipid) and virus (proteins)

Question 25

what does the viral envelope surround

Answer 25

nucleocapsid (baggy or shrink wrapped)

Question 26

what type of infections are viral envelopes associated with

Answer 26

persistent infections

Question 27

describe enveloped viruses interaction with alcohol and with the immune system

Answer 27

enveloped viruses have lipids so it is easy to eliminate them (more susceptible) with alcohols and once the surface protein on the envelope is eliminated, virus cannot carry out their function

on the other hand, enveloped viruses are harder to recognize by the immune system so that is its advantage

Question 28

two major proteins on viral envelope of influenza virus

Answer 28

hemagglutinin (surface glycoprotein)

neuraminidase (surface spikes)

Question 29

function of the viral envelope major proteins in influenza virus

Answer 29

Hemagglutinin (surface glycoprotein) - Attaches to sialic acid residues of host cell surface

Neuraminidase (surface “spike”) - Aids in release of virus from host cell

Question 30

where are nucleoproteins found

Answer 30

core of virus

Question 31

what is the function of nucleoprotein

Answer 31

required for replication strategies and to stabilize NA during replication

Question 32

what type of function do nucleoproteins typically have

Answer 32

enzymatic

Question 33

importance of matrix proteins

Answer 33

– Links envelope and capsid: stabilization
– Can drive final assembly process
– Important determinant of budding location

Question 34

what are surface proteins

Answer 34

proteins that are exposed on the surface capsid or envelope proteins (glycoproteins) and help with attachment to host cells (includes VAPs)

Question 35

shape of nucleic acid in virus

Answer 35

linear or circular or segmented

Question 36

how are viruses classified

Answer 36

baltimore classification system