2. Viruses: Chapter 13 (and a bit of Chapter 8)

Question 1

what are viruses made up of?

Answer 1

proteins and nucleic acids

Question 2

what do you mean, “virions contain only a single type of nucleic acid”?

Answer 2

either RNA or DNA, never both

Question 3

what is a capsid? what does it do?

Answer 3

protects viral nucleic acid

Question 4

what is the protein coat called?

Answer 4

capsid

Question 5

describe the genome of a viral particle

Answer 5

it may be linear or circular, and either single-stranded or double-stranded

Question 6

what do you call the capsid, together with the nucleic acid that it encloses? (don’t think too hard)

Answer 6

nucleocapsid

Question 7

list the three common shapes of viruses

Answer 7

icosahedral, helical, complex

Question 8

what is the outer lipid bilayer of a virus called?

Answer 8

the envelope

Question 9

what is the envelope of a virus?

Answer 9

an outer lipid bilayer

Question 10

non-enveloped viruses, aka…

Answer 10

nakd viruses

Question 11

where do enveloped viruses obtain their outer layer from?

Answer 11

the host cell

Question 12

which type of virus is more susceptible to soaps, detergents, and disinfectants? why?

Answer 12

enveloped. these chemicals damage the envelope, which remove the spikes. no spikes = no attachment = no infection.

Question 13

how do phages attatch? how about animal viruses?

Answer 13

tail fibers
spikes

Question 14

are bacterial viruses nakd or enveloped?

Answer 14

almost all are non-enveloped

Question 15

are animal viruses nakd, enveloped, or both?

Answer 15

either

Question 16

why do viruses need receptors?

Answer 16

they need to bind to receptors because attachment means infection

Question 17

why do viruses need a host cell?

Answer 17

viruses lack the ability to harvest energy, or synthesize proteins

Question 18

lytic phages, aka…

Answer 18

virulent phages

Question 19

virulent phages, aka…

Answer 19

lytic phages

Question 20

define lytic phages

Answer 20

a bacterial virus that lyses its host

Question 21

what is a good example of a lytic phage?

Answer 21

T4, a double-stranded DNA phage that infects E. coli

Question 22

describe the replication cycle of T4 (5)

Answer 22

1. attachment
2. genome entry
3. synthesis of phage proteins and genome
4. assembly (maturation)
5. release

Question 23

describe the attachment step of T4 replication cycle

Answer 23

phage attaches to specific receptors on E. coli cell wall

Question 24

describe the genome entry step of T4 replication cycle

Answer 24

tail contracts and phage DNA is injected into the bacterial cell, leaving the phage coat outside

Question 25

describe the synthesis of phage proteins and genome step of T4 replication cycle

Answer 25

some phage genes are quickly expressed. a phage-encoded enzyme degrades host DNA. phage DNA is replicated and other virion components are made

Question 26

describe the assembly (maturation) step of T4 replication cycle

Answer 26

phage components are assembled into mature virions

Question 27

describe the release step of T4 replication cycle

Answer 27

bacterial cell lyses and new infectious virions are released

Question 28

what are the two possible outcomes of temperate phages?

Answer 28

lytic or lysogenic infection