Ch 13 Viruses Part 1

Question 1

what are general characteristics of viruses

Answer 1

Non-living entities
	Not considered organisms
Can infect organisms of all life-forms
Obligate intracellular parasites
	Unable to reproduce outside of living cells

Question 2

what do viruses contain

Answer 2

a single type of nucleic acid

a protein coat that surrounds the nucleic acid

Question 3

where do viruses multiply and why

Answer 3

inside living cells, using the synthesizing machinery of the cell

Question 4

what do viruses cause

Answer 4

synthesis of specialized structures that can transfer the viral nucleic acid to other cells.

Question 5

describe viruses

Answer 5

Simple organization
DNA or RNA but not both (one exception)
Unable to reproduce outside of living cells
Obligate intracellular parasites

Question 6

describe cellular organisms

Answer 6

Complex organization
Both DNA and RNA
Carry out cell division
Some are obligate intracellular parasites

Question 7

Complete virus particle

Answer 7

virion

Question 8

what does a virion consist of

Answer 8

Consists of nucleic acid surrounded by protein coat

Question 9

what is the name of the protein coat

Answer 9

capsid

Question 10

describe the capsid

Answer 10

composed of capsomeres

Protects genome and aids in transfer between host cells

Question 11

virions can be what

Answer 11

naked or enveloped

Question 12

describe naked vs enveloped

Answer 12

Naked – without envelope

Enveloped – surrounded by lipid membrane

Question 13

these are membrane structures surrounding some viruses

Answer 13

viral envelopes

Question 14

(spikes) are proteins in envelope and are virus specific

Answer 14

peplomers

Question 15

Lipids and carbohydrates in envelope are usually derived from

Answer 15

host membranes

Question 16

describe the viral genome

Answer 16

Contains only single type of nucleic acid
Either DNA or RNA (never both)
Can be linear or circular
Single-stranded or double-stranded

Question 17

where does viral replication occur

Answer 17

Only multiply inside metabolizing cell

Use host machinery to support reproduction

Question 18

every virus…

Answer 18

contains information to make viral proteins, assure replication and move in and out of host cells

Question 19

what two phases to viruses live in

Answer 19

intracellular and extracellular

Question 20

extracellular vs intracellular phases

Answer 20

Extracellular phase
Metabolically inert
Intracellular phase
Metabolically active

Question 21

what are the morphological types of viruses

Answer 21

viruses have different shapes

Question 22

Shaped like hollow tubes with protein walls

Answer 22

helical capsids

Question 23

Regular polyhedron with 20 equilateral triangular faces and 12 vertices

Answer 23

Icosahedral Capsids

Question 24

what are bacteriophages classified by

Answer 24

Based on two major criteria
Phage morphology
Nucleic acid properties

Question 25

what was the oldest classification of viruses based on

Answer 25

symptomatology

Question 26

what allows for grouping of viruses into families based on genomics and structure

Answer 26

DNA sequencing

Question 27

group of viruses sharing the same genetic info and host range

Answer 27

viral species

Question 28

what are viral enzymes entirely concerned with

Answer 28

replicating/processing viral nucleic acid

Question 29

this shows the multiplication of viruses

Answer 29

one step growth curve

Question 30

what are the five steps of the lytic cycle

Answer 30

1)attachment 2)penetration 3)biosynthesis 4)maturation 5)release

Question 31

describe the attachment stage of the lytic cycle

Answer 31

``` attachment site on the virus attaches to a complementary receptor site on the bacterial cell chemical interaction(weak bonds are formed) ```

Question 32

where are the complementary receptors sites

Answer 32

bacterial cell wall

Question 33

describe the penetration stage of the lytic cycle

Answer 33

bacteriophage injects its DNA into the bacterium phage lysozome tail sheath of the phage contracts and tail is driven into cell wall

Question 34

where does the capsid remain

Answer 34

outside the bacterial cell wall

Question 35

what the bacteriophage's tail releases | enzymes that breaks down a portion of the cell wall

Answer 35

phage lysozome

Question 36

describe the biosynthesis stage of the lytic cycle

Answer 36

hose protein synthesis is stopped by virus induced degradation of the host DNA, viral proteins that interfere with transcription or repression of translation

Question 37

period during viral multiplication when complete invective virions are not yet present

Answer 37

eclipse period

Question 38

describe the maturation stage of the lytic cycle

Answer 38

bacteriophage DNA and capsids are assembled into complete virions head is filled with phage DNA and attached to the tail

Question 39

describe the release stage of the lytic cycle

Answer 39

release of virions from the hose cell lysis lysozyme

Question 40

plasma membrane actually breaks open

Answer 40

lysis

Question 41

encoded by phage gene and is synthesized within the cell this causes bacterial cell wall to break down newly produced bacteriophages are released and infect new cells

Answer 41

lysozyme

Question 42

may proceed through a lytic cycle but are capable of incorporating their DNA into the host's DNA to begin lysogenic

Answer 42

lysogenic phages

Question 43

phage remains latent(inactive)

Answer 43

lysogeny

Question 44

what are the stages of the lysogenic cycle

Answer 44

1)attachement 2)penetration 3) prophage 4)replicate prophage DNA 5)excision of DNA 6)lytic cycle

Question 45

describe the prophage of lysogenic cycle

Answer 45

circle can recombine with and become part of the circular bacterial DNA inserted phage=prophage phage genes are turned off

Question 46

describe the fourth stage of lysogenic cycle

Answer 46

replicates the prophage DNA | lysogeic bacterium produces normally

Question 47

what are the three results of lysogeny

Answer 47

1) lysogenic cells are immune to reinfection by same phage 2) phage conversion 3) specialized trandsuction

Question 48

host cell may exhibit new properties

Answer 48

phage conversion

Question 49

this occurs when only certain bacterial genes can be transferred

Answer 49

specialized transduction