chapter 5: viruses and prions

Question 1

What are some traits of a VIRUS?

Answer 1

• Acellular with a protein coat and nucleic acid genome
• Lacks independent metabolism
• Needs host cell
• Few/no enzymes
• Cannot synthesize proteins

Question 2

Viruses are known as ___

Answer 2

Filterable

Question 3

Bacteriophage

Answer 3

A virus that infects a bacteria

Question 4

Size comparison of Viruses (Yeast) vs. Bacteria

Answer 4

• Small to large
• Long
• Narrow

Question 5

What are some traits of a VIRAL STRUCTURE?

Answer 5

• Protein coat (capsid)
• Nucleocapsid - simplest form of a capsid
• Naked - a virus w/o and enevelope
• Virion - fully formed virus that can infect
• Envelope - nucleocapsid outside layer

Question 6

Which envelope proteins are involved in virus assembly?

Answer 6

Membrane protein (M) and Envelope protein (E)

Question 7

Which envelope protein mediated virus entry into host cells?

Answer 7

Spike proteins (S)

Question 8

What are SPIKES (peplomers)?

Answer 8

Proteins on outer surfaces that project externally

Question 9

What is a VIRAL CAPSID made of?

Answer 9

Capsomeres - identical protein subunits

Question 10

What are traits of a HELICAL CAPSID?

Answer 10

• Helix shaped
• Rigid, flexible
• Genome filament
• Length is long enough to cover genome

Question 11

What are traits of a ICOSAHEDRAL CAPSID?

Answer 11

• Variations in the # of capsomeres
• Some have spikes
• Variety in shape

Question 12

What are traits of a COMPLEX CAPSID?

Answer 12

• Elaborate structure found in bacteriophages
• Not symmetrical
• No envelopes

Question 13

What are traits of a VIRAL GENOME?

Answer 13

• 4 types: DS DNA, SS DNA, DS RNA, SS RNA
• Genome can be circular or linear

Question 14

What are the phases of ANIMAL VIRAL REPLICATION?

Answer 14

• Absorption
• Penetration and un-coating
• Synthesis
• Assembly
• Release

Question 15

How do viruses ATTACH or ABSORB?

Answer 15

Attach via spikes or capsid –> receptors on host cell surface

Question 16

How do viruses PENETRATE or UN-COATING?

Answer 16

Entire virus/genome enters host

Question 17

How do viruses REPLICATE?

Answer 17

• Genome transcribed and translated
• Synthesizes building blocks for new viruses once inside host
• DNA viruses enter host cells’ nucleus and replicate

Question 18

DNA virus process

Answer 18

DNA has info -> Replicates -> mRNA made -> mRNA decoded and proteins

Question 19

How do viruses REPLICATE? (positive)

Answer 19

• RNA replicates and assembled in cytoplasm
• Carry in proteins to complete synthesis
• ssRNA is translated into viral proteins

Question 20

How do viruses REPLICATE? (negative)

Answer 20

• ssRNA cannot serve as mRNA to form viral proteins, uses
  – ssRNA as
  template for +ssRNA
• New + strand intermediates synthesized
• Newly synthesized + strand serves as template for more -ssRNA
  synthesis & mRNA

Question 21

How do viruses REPLICATE? (dsRNA)

Answer 21

• dsRNA as a template for mRNA
• Virus transcribed dsRNA –> +ss RNA

Question 22

How do viruses ASSEMBLE?

Answer 22

Construction from various viral parts

Question 23

How do viruses RELEASE?

Answer 23

• Via host cell lysis
• Non-enveloped viruses and phages
• Lysozyme attacks PG in host and releases virus
• Protein (holin) creates holes in cytoplasmic membrane
• Lysozyme acceses cell wall

Question 23

How do viruses RELEASE?

Answer 23

• Via host cell lysis
• Non-enveloped viruses and phages
• Lysozyme attacks PG in host and releases virus
• Protein (holin) creates holes in cytoplasmic membrane
• Lysozyme acceses cell wall

Question 24

What is BUDDING?

Answer 24

.

Question 25

What is CYTOCIDAL INFECTION?

Answer 25

Viral infection that results in cell death where the host cell lyses