Chapter 3

Question 1

What are the three primary components of a virus particle?

Answer 1

viral nucleic acid, capsid, and lipid envelope

Question 2

What is a virus particle also known as?

Answer 2

virion

Question 3

True or False: All viruses are composed of RNA.

Answer 3

False: viruses can be composed of either RNA or DNA

Question 4

Are viruses haploid or diploid organisms?

Answer 4

haploid

Question 5

Define capsid.

Answer 5

a protein shell that surrounds the viral nucleic acid (genetic material) of the virus

Question 6

What is the capsid composed of?

Answer 6

smaller repetitive protein subunits termed capsomers

Question 7

True or false: All viruses have the lipid envelope

Answer 7

false

Question 8

What is the lipid envelope made up of?

Answer 8

a lipid bilayer derived by budding from a host cell membrane and is embedded with glycoproteins

Question 9

What is a capsomer?

Answer 9

identical protein subunits that make up the capsid

Question 10

What makes up a capsomer?

Answer 10

1 to 6 or 7 individual proteins called protomers

Question 11

What are the two basic types of capsid symmetry?

Answer 11

Icosahedral and helical

Question 12

Describe the Icosahedral shape.

Answer 12

closed structure composed only of a single repeating subunit

Question 13

All animal viruses with helical symmetry are _____ ___ __ _______.

Answer 13

surrounded by an envelope

Question 14

What are the three functions of the capsid?

Answer 14

• Protects the nucleic acid
• Interacts with viral and cellular proteins to promote packaging of the viral genome and assembly of the virus particle
• Interacts with cellular proteins during virus entry and exit from the cell

Question 15

How is a viral envelope acquired?

Answer 15

by budding through a host cell membrane (usually a plasma membrane)

Question 16

What is the function of the glycoprotein molecules in the viral envelope?

Answer 16

facilitate entry and exit from the host cell

Question 17

What is a peplomer?

Answer 17

glycoproteins contained within the envelope

Question 18

What are the three structural proteins of a virion?

Answer 18

matrix, nucleocapsid, and tegument

Question 19

Define matrix.

Answer 19

non-glycosylated proteins found on the inner layer of the envelope

Question 20

Define nucleocapsid.

Answer 20

the protein layer surrounding the viral genomic nucleic acid

Question 21

In many cases, what is the nucleocapsid?

Answer 21

the capsid protein

Question 22

Define tegument.

Answer 22

an amorphous protective protein layer between the capsid and envelope of herpes viruses

Question 23

Give examples of 2 non-structural proteins.

Answer 23

polymerase and regulatory/accessory proteins

Question 24

What is a polymerase?

Answer 24

virus-encoded enzymes required for biosynthesis viral nucleic acid and proteins

Question 25

What is the function of regulatory/accessory proteins?

Answer 25

function to provide intracellular environment that promotes biosynthesis of viral proteins and nucleic acid

Question 26

Are enveloped viruses or non-enveloped viruses more fragile?

Answer 26

enveloped

Question 27

Why are enveloped viruses more fragile?

Answer 27

- more heat liable - more susceptible to freezing and thawing - more susceptible to desiccation

Question 28

What is a viral serotype?

Answer 28

a set of viruses that can be distinguished from other viruses in the same species on the basis of antigenic properties

Question 29

What is a 'strain'?

Answer 29

a term used to denote different viruses of the same serotype, but with only minor differences in biological phenotype

Question 30

What is an 'isolate'?

Answer 30

sample of a virus from a single, defined source

Question 31

What are most viruses transmitted by?

Answer 31

inhalation, ingestion, injection, close contact, or congenitally

Question 32

Define respiratory viruses.

Answer 32

term is usually restricted to viruses that remain localized in the respiratory tract, rather than causing generalized infections

Question 33

Typically, how are respiratory viruses acquired?

Answer 33

inhalation or fomites

Question 34

Define enteric viruses.

Answer 34

term usually restricted to viruses that remain localized in the intestinal tract, rather than causing generalized infections

Question 35

Typically, how are enteric viruses acquired?

Answer 35

by ingestion (and replicate in intestinal tract)

Question 36

Define arbovirus.

Answer 36

an arthropod-borne virus that replicates in blood-feeding arthropod vectors and is transmitted by bites to vertebrate hosts

Question 37

What are oncogenic viruses?

Answer 37

viruses that usually infect specific cells, where they become persistent and may evoke transformation

Question 38

What questions need to be answered for classification of viruses at the family level?

Answer 38

- What type of nucleic acid does it have? - Does the virus have an envelope? - Is the viral genome segmented or not?