CHAPTER 13: VIRUSES AND PRIONS || 100% CORRECT
ANSWERS.
83. What are the 10 general characteristics of viruses? correct answers 1) not considered
living
2) obligate intracellular parasites
3) ultra microscopic size
4) no cellular in nature (structure = compact and economical)
5) protein shell (capsid)
6) nucleic acid can either be DNA or RNA and can either be singled or double stranded
7) molecules on surface to attach to host cell
8) multiply by taking control of host cells genetic material and regulating the synthesis and
assembly of new viruses
9) lack enzymes for metabolic processes
10) lack machinery for synthesizing protein
84. What is the term for the fully formed virus that is able to establish an infection? correct
answers Virion
85. What are viruses classified by? (3) correct answers 1) Type of nucleic acid - DNA or
RNA (single or double stranded)
2) Morphology
3) Replication strategy (w/in the host cell)
86. Are antimicrobial drugs more likely to be effective towards naked or enveloped viruses?
Why? correct answers Enveloped viruses. Most sensitive to antimicrobial chemicals because
most are lipid soluble (dissolves phospholipids) & viruses will no longer be able to attach to
host.
87. What are the two parts of the nucleocapsid? correct answers 1) nucleic acid (core)
2) (protein) capsid
88. What nucleic acid(s) are found in viruses? What are some of the possible structures of
viral DNA (e.g single stranded, circular, etc.)? What types of genes are typically in a viral
genome? correct answers Either DNA or RNA (never both) - maybe segmented
Single stranded, double stranded, linear or circular
Carries genes necessary to invade host cell and redirect cell's activity to make new viruses.
Number of genes varies for each type of virus - few to hundreds
89. What is a capsid and what is it made of? correct answers All viruses have capsids -
protein coats that enclose and protect their nucleic acid
Constructed from identical repeatedly sub units called capsomers made of protein - some
have an external covering (envelope) and some lack it (naked)
90. What are the identical protein subunits called that make up a capsid called? correct
answers Capsomers.
, 91. What is the viral envelope and what is it composed of? Where is the viral envelope,
relative to the capsid (inside or outside?)? Are enveloped viruses monomorphic or
pleomorphic? What advantage does the viral envelope give a virus? correct answers F(x) = to
hide from the hosts immune system
A phospholipid layer; only in some viruses - usually in animal viruses
Composed of host cell membrane (acquired when the virus leaves the host cell)
surrounds the capsid
Pleomorphic (many shapes)
Exposed carbohydrate-protein complexes on the outside of the envelope called spikes
92. What are the spikes used for on a viral envelope? correct answers Essential for attachment
of the virus to the host cell.
93. What are the 4 enzymes that viruses can produce? Which enzyme do retroviruses use to
direct the formation of DNA from RNA? correct answers 1) Polymerase: synthesize of DNA
and RNA
2) Replicases: copy RNA (RNA > RNA)
3) Reverse transcriptase: synthesis of DNA from RNA (RNA > DNA). Known as
retroviruses - used for viruses that RNA as their genetic information. Ex. HIV
4) Lysozyme: enzyme to degrade cell walls - found in bacteriophage (viruses that effect
bacteria)
What are the 4 types of viral shape? correct answers 1) Helical
2) Polyhedral
3) Complex
4) Enveloped
1)Helical
2) Polyhedral
3)Complex
4)Enveloped correct answers 1) The virus capsid shape that is a hollow cylinder with nucleic
acid inside. Ex. Ebola or rabies
2) The virus capsid shape that is many sided; icosahedron. Ex. adehovirus - effects respiration
system
3) Have both a helical and polyhedral shape. Ex. bacteriophage
4) Roughly spherical, but are polymorphic (many shapes). The capsid inside the envelope can
either be helical or polyhedral. Ex. influenza virus.
ANSWERS.
83. What are the 10 general characteristics of viruses? correct answers 1) not considered
living
2) obligate intracellular parasites
3) ultra microscopic size
4) no cellular in nature (structure = compact and economical)
5) protein shell (capsid)
6) nucleic acid can either be DNA or RNA and can either be singled or double stranded
7) molecules on surface to attach to host cell
8) multiply by taking control of host cells genetic material and regulating the synthesis and
assembly of new viruses
9) lack enzymes for metabolic processes
10) lack machinery for synthesizing protein
84. What is the term for the fully formed virus that is able to establish an infection? correct
answers Virion
85. What are viruses classified by? (3) correct answers 1) Type of nucleic acid - DNA or
RNA (single or double stranded)
2) Morphology
3) Replication strategy (w/in the host cell)
86. Are antimicrobial drugs more likely to be effective towards naked or enveloped viruses?
Why? correct answers Enveloped viruses. Most sensitive to antimicrobial chemicals because
most are lipid soluble (dissolves phospholipids) & viruses will no longer be able to attach to
host.
87. What are the two parts of the nucleocapsid? correct answers 1) nucleic acid (core)
2) (protein) capsid
88. What nucleic acid(s) are found in viruses? What are some of the possible structures of
viral DNA (e.g single stranded, circular, etc.)? What types of genes are typically in a viral
genome? correct answers Either DNA or RNA (never both) - maybe segmented
Single stranded, double stranded, linear or circular
Carries genes necessary to invade host cell and redirect cell's activity to make new viruses.
Number of genes varies for each type of virus - few to hundreds
89. What is a capsid and what is it made of? correct answers All viruses have capsids -
protein coats that enclose and protect their nucleic acid
Constructed from identical repeatedly sub units called capsomers made of protein - some
have an external covering (envelope) and some lack it (naked)
90. What are the identical protein subunits called that make up a capsid called? correct
answers Capsomers.
, 91. What is the viral envelope and what is it composed of? Where is the viral envelope,
relative to the capsid (inside or outside?)? Are enveloped viruses monomorphic or
pleomorphic? What advantage does the viral envelope give a virus? correct answers F(x) = to
hide from the hosts immune system
A phospholipid layer; only in some viruses - usually in animal viruses
Composed of host cell membrane (acquired when the virus leaves the host cell)
surrounds the capsid
Pleomorphic (many shapes)
Exposed carbohydrate-protein complexes on the outside of the envelope called spikes
92. What are the spikes used for on a viral envelope? correct answers Essential for attachment
of the virus to the host cell.
93. What are the 4 enzymes that viruses can produce? Which enzyme do retroviruses use to
direct the formation of DNA from RNA? correct answers 1) Polymerase: synthesize of DNA
and RNA
2) Replicases: copy RNA (RNA > RNA)
3) Reverse transcriptase: synthesis of DNA from RNA (RNA > DNA). Known as
retroviruses - used for viruses that RNA as their genetic information. Ex. HIV
4) Lysozyme: enzyme to degrade cell walls - found in bacteriophage (viruses that effect
bacteria)
What are the 4 types of viral shape? correct answers 1) Helical
2) Polyhedral
3) Complex
4) Enveloped
1)Helical
2) Polyhedral
3)Complex
4)Enveloped correct answers 1) The virus capsid shape that is a hollow cylinder with nucleic
acid inside. Ex. Ebola or rabies
2) The virus capsid shape that is many sided; icosahedron. Ex. adehovirus - effects respiration
system
3) Have both a helical and polyhedral shape. Ex. bacteriophage
4) Roughly spherical, but are polymorphic (many shapes). The capsid inside the envelope can
either be helical or polyhedral. Ex. influenza virus.
