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Biology - MCAT > Class Four > Flashcards

Class Four Flashcards

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1
Q

viruses are classified as..

A

obligate intracellular parasites

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2
Q

are viruses cells or living organisms

A

neither

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3
Q

how do viruses reproduce

A

by taking over the cellular machinery of their host cell

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4
Q

can viruses produce ATP

A

no - but some store it in their capsids (from their previous host)

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5
Q

all viruses possess..

A

a nucleic acid genome packaged in a protein shell

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6
Q

purpose of a virus’ protein shell

A

allows to convey the genome from one cell to infect other cells

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7
Q

a viral genome consists of..

A

DNA or RNA

single OR double stranded

linear OR circular

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8
Q

how many types of nucleic acids in a virus genome

A

only one

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9
Q

a factor that influences all virus genomes - limiting factor

A

size - viruses are super tiny

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10
Q

is the exterior protein shell of a virus rigid or flexible

A

rigid - cannot accommodate a larger genome

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11
Q

2 adaptions of viruses (size constraint)

A

only carry few genes (uses host proteins for transcription/translation/replication)

able to encode more than one protein in a given length of genome - uses more than one reading frame (genes overlap)

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12
Q

protein coat of viruses aka..

A

capsid

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13
Q

helical vs polyhedral capsids

A

helical = rod shaped

polyhedral = multisided geometric shapes

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14
Q

what do we use to classify viruses

A

their capsids

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15
Q

host for T4 bacteriophage

A

E.coli

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16
Q

where is the virus genome located

A

capsid head

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17
Q

what do the tail fibers and base plate do

A

attach to the surface of the host cell

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18
Q

how does virus sheath contract

A

using stored ATP - injects genome into host

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19
Q

viral capsid is composed of..

A

protein

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20
Q

viral genome is composed of..

A

nucleic acid (DNA or RNA)

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21
Q

where does the envelope around the capsid come from

A

derived from the membrane of the host cell

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22
Q

viruses that don’t have envelopes are..

A

naked viruses

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23
Q

what does an envelope contain

A

phospholipids/proteins/carbohydrates from host cell

+

proteins encoded by viral genome

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24
Q

why don’t plant cells have envelopes

A

they infect hosts with cell walls - no budding through the host cell membrane

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25
Q

2 ways viruses can be internalized

A

fusion with the plasma membrane OR

repeptor-mediated endocytosis

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26
Q

what is an early gene + example

A

group of genes immediately expressed after infection

hydrolase

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27
Q

what does hydrolase do right after infection

A

degrades the entire host genome

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28
Q

lysozyme is an example of a..

A

late gene

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29
Q

how are multiple copies of the phage genome produced

A

using the dNTPs resulting from the degradation of the host genome

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30
Q

function of lysozyme

A

destroys bacterial cell walls - all the produced viruses can escape

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31
Q

why is it important that lysozyme is a late gene

A

don’t want the host cell to lyse before the phage had time to replicate and assemble

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32
Q

first 2 steps of the bacteriophage life cycle

A

attachment/adsorption

penetration/eclipse

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33
Q

after the penetration step, viruses can enter..

A

the lytic or lysogenic cycles

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34
Q

what is a prophage

A

phage genome incorporated into the bacterial genome

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35
Q

what is the host called after prophage forms

A

lysogen

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36
Q

why are prophages dormant

A

transcription of phage genes is blocked by a phage-encoded repressor

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37
Q

lysogenic cycle - as host cell replicates..

A

so does the prophage

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38
Q

what type of viruses enter through endocytosis

A

animal viruses

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39
Q

what is endocytosis

A

a process where the host cell engulfs the virus + internalizes it

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40
Q

difference between lytic cycle and productive cycle

A

productive cycle is similar but does not destroy the host cell

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41
Q

what allows for the productive cycle

A

enveloped viruses exiting via budding and not lysis

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42
Q

(+) RNA viruses must..

A

encode RNA-dependent RNA pol (but don’t have to carry it)

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43
Q

what is a (+) RNA

A

a single stranded RNA which serves as mRNA

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44
Q

(-) RNA viruses must..

A

carry RNA-dependent pol (and encode it)

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45
Q

retroviruses must..

A

encode reverse transcriptase

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46
Q

3 main retroviral genes

A

gag: codes for viral capsid proteins
pol: polymerase codes for reverse transcriptase)
env: envelope codes for viral envelope proteins

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47
Q

double stranded DNA viruses often..

A

encode enzymes required for dNTP synthesis and DNA replication

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48
Q

what are subviral particles

A

infectious agents that are smaller and simpler than viruses

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49
Q

how do prions not follow the central dogma

A

they are self-replicating

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50
Q

how do prions affect normally folded proteins

A

comes into contact with them → prions act as a temple → protein is altered + becomes infectious

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51
Q

what is responsible for transmissible spongiform encephalopathies

A

prions

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52
Q

transmissible spongiform encephalopathies cause..

A

degeneration in the nervous system - holes in the brain

53
Q

mad cow disease is caused by..

A

prions

54
Q

why are prions hard to destroy

A

resistant to degradation by chemicals or heat

55
Q

what is a viroid

A

short piece of circular, single stranded RNA - can base pair with itself

56
Q

how do viroids work

A

hijack the cell’s DNA dependent RNA polymerase and directs it to read RNA templates

57
Q

human disease linked to viroids

A

Hepatitis D

58
Q

do viroids have capsids

A

no

59
Q

who discovered cell theory

A

Robert Hooke

60
Q

3 tenets of cell theory

A

all living organisms are composed of 1+ cells

cells are the monomer for any organism

new cells arise form pre-existing, living cells

61
Q

main difference between prokaryotes and eukaryotes

A

prokaryotes do not contain membrane bound organelles - no nucleus

62
Q

classification of living organisms aka

A

taxonomy

63
Q

three domains of taxonomy

A

bacteria

archea

eukarya

64
Q

3 eukaryotic kingdoms

A

animalia, plantae and fungi

65
Q

prokaryotic genome is..

A

a single double stranded DNA chromosome

66
Q

why does streptomycin only affect bacterial translation and not ours

A

structural differences in bacterial and eukaryotic ribosomes

67
Q

what is the plasmid

A

circular piece of ds DNA - smaller than genome

encodes advantageous gene products

68
Q

three shapes of bacteria

A

round (cocci)

rod-shaped (bacilli)

spiral-shaped (spirilla)

69
Q

bacterial cell wall is composed of..

A

peptidoglycan

70
Q

what is unique about peptidoglycan

A

has D-alanine (not found in animal cells)

71
Q

what does lysozyme target

A

peptidoglycan

72
Q

what happens when peptidoglycan is destroyed

A

cell becomes a protoplast - fragile and prone to lysis

73
Q

gram pos vs gram neg

A

gram pos stains strongly

gram neg stains poorly

74
Q

gram staining differs among..

A

2 different types of bacterial cell walls

75
Q

gram positive bacterial walls have..

A

a thick peptidoglycan layer as its outermost layer

76
Q

gram negative bacterial walls have..

A

thinner peptidoglycan layer with an outer layer with lipopolysaccharide

77
Q

what is the periplasmic space

A

in gram neg bacteria

space between cell membrane and outer layer

78
Q

what are endotoxins

A

found in the outer membrane of gram neg bacteria

not poisonous but cause our immune system to have extreme reactions (septic shock)

79
Q

what are exotoxins

A

very toxic substances secreted by gram neg and gram pos bacteria

allows the bacteria to compete with other bacteria

80
Q

what is the bacterial capsule

A

sticky layer of polysaccharide goo that surrounds the bacterial cell

makes it harder for the immune system to kill it

allows bacteria to stick to smooth surfaces (human GI tract)

81
Q

how do bacteria move

A

with flagella

82
Q

what is motile bacteria

A

bacteria with more than one flagella

83
Q

monotrichous bacteria

A

one flagellum at one end

84
Q

amphitrichous bacteria

A

flagellum at both ends

85
Q

peritrichous bacteria

A

they have multiple flagella

86
Q

3 major components of flagella

A

filament, hook and basal structure

87
Q

purpose of the basal structure of flagella

A

anchors the flagellum to the bacteria

rotates the rod

88
Q

rotation of rod (flagella) is powered by..

A

the diffusion of H+ down the proton gradient

89
Q

chemoreceptors role in flagella movement

A

flagellar rotation occurs to move away from high conc of chemical

chemoreceptors transmits the signal to let the flagella know which way to rotate

90
Q

what are pili

A

long projections on the bacterial surface (allows for attachment to other surfaces)

91
Q

sex pilus

A

attaches male and female bacteria to form conjugation bridges

92
Q

purpose of fimbriae

A

involved in adhering to surfaces

93
Q

mesophiles

A

bacteria that favours mild temperatures (like humans)

94
Q

thermophiles

A

bacteria that thrives in hot temperatures

95
Q

psychrophiles

A

bacteria that thrives in low temperatures

96
Q

autotrophs

A

bacteria that use CO2 as their carbon source

97
Q

heterotrophs

A

rely on nutrients created by other organisms (glucose)

98
Q

chemotrophs

A

get their energy from chemicals

99
Q

phototrophs

A

get their energy from light

100
Q

common medium for bacteria

A

agar

101
Q

what is minimal medium

A

agar + glucose

102
Q

bacterial lawn

A

dense growth of bacteria in a Petri dish

103
Q

what is the doubling time

A

amount of time required for a population of bacteria to double its number

104
Q

what is an auxotroph

A

bacteria that needs a molecule to live

requires an auxiliary trophic substance to live

needs to have this substance in their medium

105
Q

bacteria which require oxygen are..

A

obligate aerobes

106
Q

bacteria which don’t require oxygen are..

A

anaerobes

107
Q

facultative, tolerant vs obligate anaerobes

A

facultative: will use oxygen if its there but don’t need it
tolerant: don’t use oxygen in their metabolism (indifferent)
obligate: poisoned by oxygen

108
Q

how does bacteria reproduce

A

asexually

109
Q

how does bacteria exchange information

A

through conjugation

110
Q

4 phases of bacterial reproduction

A

lag phase

log phase

stationary phase

death phase

111
Q

maximum population at stationary phase =

A

carrying capacity

112
Q

what type of bacteria forms endospores

A

gram pos

113
Q

when are endospores formed

A

in unfavourable conditions

114
Q

structure of endospores

A

tough, thick external shells comprised of peptidoglycan

inside the spore: genome, ribosomes & RNA

115
Q

3 ways bacteria acquires new genetic material

A

transduction

transformation

conjugation

116
Q

what is bacterial transduction

A

transfer fo genomic DNA from one bacteria to another by a lysogneic phage

117
Q

what is bacterial transformation

A

bacteria can internalize pure DNA in certain conditions

118
Q

a key to bacterial conjugation

A

the F (fertility) factor

bacteria that has it = male

119
Q

hows does a conjugation bridge form

A

male cell produces sex pili → contacts a female cell to form the conjugation bridge

F factor is replicated and goes to the female cell

120
Q

a cell with the F factor integrated into its genome =

A

Hfr

high frequency of recombination cell

121
Q

characteristics of archaea

A

live in very extreme conditions

single celled

reproduce via fission or budding

122
Q

parasites and host cells

A

parasites cause damage to the host cell

123
Q

symbiotic bacteria and host cells

A

they coexist

both cells benefit

124
Q

+ RNA has to be able to code for..

A

RNA dependent RNA polymerase

125
Q

(-) RNA must..

A

carry RNA dependent RNA polymerase and be able to code for it

126
Q

problems with retroviruses

A

permanently in genome

rapid mutations

127
Q

what shape is E. coli

A

bacillus

128
Q

which gram is more antibiotic resistant

A

gram neg

has enzymes that degrade antibiotics in their periplasmic space

Biology - MCAT (11 decks)

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