Ch. 5: Microbiology

Question 1

structure of

virus

Answer 1

obligate intracellular parasite

protein + nucleic acid

Question 2

two basic steps of viral life cycle

Answer 2

(1) attachment / adsorption
- virus finds & binds to surface of host cell
- very specific
- not yet infected

(2) injection (penetration)
- virus injects genome into the host cell
- host is infected

Question 3

summary of

lytic cycle

Answer 3

(1) transcribe & translate the viral genome
(2) replicate the viral genome
(3) lysis of host & release of new viral particles

Question 4

step #1

lytic cycle

Answer 4

(1) transcribe & translate the viral genome
- early genes: hydrolase, capsid proteins
- hydrolase destroys host cell genome
- all cellular energy directed toward viral protein synthesis
- creates a pool of NTPs for viral genome replication

Question 5

step #2

lytic cycle

Answer 5

(2) replicate the viral genome
- capsid assembles automatically around the genome copies

Question 6

step #3

lytic cycle

Answer 6

(3) lysis of host & release of new viral particles
- late genes: lysozyme
- enzymes that put holes in bacterial cell wall

Question 7

summary of

lysogenic cycle

Answer 7

(1) integrate viral genome with host genome
(2) normal host activity, including reproduction
(3) excision & lytic cycle

Question 8

step #1

lysogenic cycle

Answer 8

(1) integrate viral genome with host genome

Question 9

step #2

lysogenic cycle

Answer 9

(2) normal host activity, including reproduction

Question 10

step #3

lysogenic cycle

Answer 10

(3) excision & lytic cycle
- triggered by stress on host cell
- requires removal of repressors
- transduction: transfer of host DNA to a new host via bacteriophage

Question 11

productive cycle

Answer 11

ANIMAL CELL VIRUSES ONLY
- like the lytic cycle, but without lysis
- new viruses leave host cell by budding out of cell membrane, “enveloped virus”

Question 12

advantages of

productive cycle

Answer 12

(1) more viral copies from one host cell
(2) develop an envelop
- slight evasion from immune system
- easier infection

Question 13

characteristics of

prions

Answer 13

“infectious protein”
- no DNA or RNA
- no membranes
- no organelles
- very small
- extremely stable

Question 14

two categories of

prions

Answer 14

(1) normal prions: good, neuroprotective
(2) mutant prions: bad, neurodegenerative

ex: mad cow disease (spongiform encephalopathies)

Question 15

how do mutant “bad” prions arise?

Answer 15

(1) spontaneously arise due to a mutation
(2) can be inherited
(3) be transmitted by consuming diseased tissue (zombie infection)

Question 16

characteristics of

viroids

Answer 16

“virus like”
- circular RNA (+ or – sense)
- no capsid
- must be coinfected
- don’t code for proteins
- act as miRNAs or siRNAs to block translation

Question 17

shape

bacterial classification: structure

Answer 17

• circular: “…coccus”
• oval: “…bacillus”
• curly “…spirellum”

Question 18

cell wall/membranes

bacterial classification: structure

Answer 18

cell wall + cell membrane
- gram (+) positive
- dark purple

outer membrane + cell wall + inner membrane
- gram (–) negative
- light pink

Question 19

flagella

bacterial classification: structure

Answer 19

“…trichous”

1 = mono…
2 = amphi…
many = peri…

Question 21

temperature

bacterial classification: living conditions

Answer 21

• hot (100º C): thermophiles
• medium (30º C): mesophiles
• cold (0º C) psychophiles

Question 21

oxygen use

obligate aerobe

bacterial classification: living conditions

Answer 21

oxygen present: use it & survive
oxygen absent: die

Question 22

oxygen use

obligate aerobe

bacterial classification: living conditions

Answer 22

oxygen present: use it & survive
oxygen absent: die

Question 23

temperature

bacterial classification: living conditions

Answer 23

• hot (100º C): thermophiles
• medium (30º C): mesophiles
• cold (0º C) psychophiles

Question 24

obligate aerobe

oxygen use

bacterial classification: living conditions

Answer 24

O2 present: use it, survive
O2 absent: die

Question 25

facultative anaerobe

oxygen use

bacterial classification: living conditions

Answer 25

O2 present: use it, survive
O2 absent: ferment, survive

Question 26

tolerant anaerobe

oxygen use

bacterial classification: living conditions

Answer 26

O2 present: doesn’t use it, doesn’t die
O2 absent: ferment, survive

Question 27

obligate anaerobe

oxygen use

bacterial classification: living conditions

Answer 27

O2 present: die
O2 absent: ferment, survive

Question 28

ultimate energy source

energy/nutrients

bacterial classification: living conditions

Answer 28

• photo: make energy from sun
• chemo: make energy from chemicals

Question 29

where carbon chains come from

energy/nutrients

bacterial classification: living conditions

Answer 29

• auto: make your own chains from CO2 in environment (DIY)
• hetero: consume other organisms

Question 30

auxotroph

energy/nutrients

bacterial classification: living conditions

Answer 30

means “can’t do something” with a particular nutrient

• AA = can’t make it, must be provided in medium/diet
• sugars = can’t metabolize it, must provide alternative sugar

Question 31

summary of

binary fission

Answer 31

• big increase in population size
• no change in genetic diversity

Question 32

three phases of binary fission

bacteria

Answer 32

(1) lag phase: adjusting to environment
(2) log phase: exponential growth
(3) stationary phase: cell death ≈ cell birth
(4) death phase: build-up of toxic byproducts, avoid by increasing carrying capacity (K)

Question 33

summary of

conjugation

bacteria

Answer 33

• big increase in genetic diversity
• no change in population size