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Cell Bio > Chp. 15 > Flashcards

Chp. 15 Flashcards

1
Q

Contains many metabolic pathways, protein synthesis, and cytoskeleton

A

Cytosol

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2
Q

Synthesis of most lipids, synthesis of proteins for distribution to many organelles and to plasma membrane

A

ER

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3
Q

Modification, sorting, packing of proteins and transport

A

Golgi

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4
Q

Intracellular degradation

A

Lysosomes

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5
Q

Sorting of endocytosed material

A

Endosomes

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6
Q

oxidative breakdown of toxic molecules

A

Peroxisomes

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7
Q

Membr ane-enclosed organelles occupy nearly __ of the cell volume

A

50%

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8
Q

Membrane-bound organelles allow __ of different cellular functions

A

spatial separation

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9
Q

With the exception of the nucleus, these organelles communicate extensively with one another and with the outside of the cell via

A

vesicular traffic

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10
Q

Nuclear envelope and the membranes of the ER, Golgi apparatus, endosomes and lysosomes likely originated by

A

invagination of the
plasma membrane

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11
Q

Mitochondria and chloroplasts likely evolved from

A

bacteria that
were engulfed by primitive eukaryotic cells

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12
Q

Mitochondria and chloroplasts remain…

A

isolated from the vesicular traffic

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13
Q

Protein transport begins with a

A

Signal sequence

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14
Q

The synthesis of virtually all proteins begins in the

A

Cytosol

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15
Q

The fate of each protein depends on whether it contains a

A

signal sequence, which directs the protein to a particular
organelle

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16
Q

Proteins that lack a signal sequence remain in the

A

Cytosol

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17
Q

The mechanism by which a protein is transported into an
organelle depends on the

A

Organelle

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18
Q

Transport of folded proteins into

A

Nucleus through nuclear pore

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19
Q

Transport of unfolded
proteins into the

A

ER, mitochondria or chloroplasts across their membranes by
protein translocators

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20
Q

Transport of proteins in
transport vesicles that

A

pinch
off from the ER and fuse
with a compartment of the
endomembrane system

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21
Q

On the cargo protein is it sequence specific signal

A

Yes

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22
Q

Signal sequence is recognized by

A

receptor proteins

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23
Q

Directional movement by transport machinery requires

A

Energy

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24
Q

Large pore, competent for fully folded proteins/complexes. GTP hydrolysis provides energy

A

nuclear import

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25
Q

narrow translocation channel;
proteins are unfolded and pulled into organelles by chaperone proteins (which hydrolyze ATP for energy)

A

Mitochondria/chloroplasts

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26
Q

Proteins enter as they are being synthesized in the

A

ER

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27
Q

__ are more important than the exact sequence

A

Hydrophobicity or the order of charged amino acids

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28
Q

Deleting a signal sequence from an ER protein converts it into a

A

cytosolic protein

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29
Q

Adding an ER signal sequence to a cytosolic protein directs it to the

A

ER

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30
Q

The outer nuclear membrane is continuous with the

A

ER

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31
Q

What part of the nucleus contains proteins that act as
binding sites for chromosomes and the nuclear lamina

A

Inner nuclear membrane

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32
Q

Transport across the nuclear
envelope occurs through

A

Nuclear pores

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33
Q

Nuclear pore complex acts as a

A

Selective gate

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34
Q

Many of the proteins that line this are unstructured and form a mesh that fills the pore, preventing passage of large molecules

A

Nuclear pore complex

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35
Q

Large structure composed of ~30 different proteins

A

Nuclear pore complex

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36
Q

Proteins enter the nucleus in what state

A

Mature, fully folded

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37
Q

Signal sequence that directs transport
into the nucleus is called a

A

Nuclear localization signal

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38
Q

NLS is recognized and bound by a cytosolic protein called a

A

Nuclear import receptor

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39
Q

facilitates nuclear transport

A

GTP hydrolysis

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40
Q

present in high concentrations in the nucleus

A

Ran-GTP

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41
Q

present in high concentrations in the cytosol

A

Ran-GDP

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42
Q

small monomeric GTPase

A

Ran

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43
Q

In the __, Ran GTP binds a

A

Nucleus, Nuclear import receptor

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44
Q

The import receptor, bound to __, returns to the __

A

Ran-GTP, cytosol

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45
Q

Hydrolysis of GTP causes…

A

Ran-GDP to release the import receptor

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46
Q

Proteins must unfold to enter

A

Mitochondria or chloroplasts

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47
Q

help pull in and refold proteins (use energy from
ATP hydrolysis)

A

Mitochondrial chaperone proteins

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48
Q

Simultaneous transport across the outer and inner membranes by __. The protein is __ during the transfer process

A

Protein translocaters, unfolded

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49
Q

Two types of proteins are transferred to the ER

A

Soluble, transmembrane

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50
Q

are translocated across the membrane into the ER lumen

A

Soluble proteins

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51
Q

are partly translocated across the membrane and
remain embedded in it

A

Trans membrane proteins

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52
Q

Proteins enter the ER while being synthesized and are directed there
by a

A

Hydrophobic ER signal sequence

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53
Q

A protein will not re enter the cytosol once inside the __. Instead, proteins are transported to their destination in __

A

ER lumen, or embedded in ER membrane; transport vesicles

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54
Q

Mos t proteins are threaded across the __ membrane before they are completely synthesized

A

ER

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55
Q

Membrane-bound ribosomes
create the

A

Rough ER

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56
Q

The ribosome synthesize the protein attached to the

A

ER membrane to initiate transfer

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57
Q

The same pool of ribosomes synthesizes

A

cytosolic proteins and ER proteins

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58
Q

Membrane-bound and free
(cytosolic) ribosomes are

A

Structurally identicical

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59
Q

When a ribosome is
synthesizing a protein with an
ER signal sequence, the signal
sequence directs the ribosome
To the

A

ER

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60
Q

Many ribosomes can bind the
same __ molecule, forming
a __

A

MRNA, polyribosome

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61
Q

binds both the ribosome and the ER signal sequence as it emerges from the ribosome

A

Signal recognition particle

62
Q

Protein synthesis slows down until the SRP binds an __ in
the ER membrane

A

SRP receptor

63
Q

Once SRP binds to an SRP receptor, the SRP is __ and passed to a __

A

Released, protein translocater

64
Q

Soluble proteins made in the ER are released into the

A

ER lumen

65
Q

The ER signal sequence opens the __ and remains bound during synthesis

A

P rotein translocator

66
Q

initiates transfer into the ER

A

N-terminal ER signal sequence

67
Q

located further along the polypeptide chain, halts the
transfer

A

stop-transfer sequence

68
Q

Once the N terminal signal sequence is cleaved, the __ remains in the belayer, forming an __

A

Stop transfer sequence, alpha helix

69
Q

The protein has a defined and permanent orientation. What is it?

A

N -terminus in the ER lumen,
and C-terminus in the cytosol

70
Q

In some proteins, an internal signal sequence called a __ initiates protein transfer into the ER

A

start-transfer sequence

71
Q

Start-transfer sequences and stop-transfer sequences can work in

A

Pairs to thread multi pass transmembrane proteins into ER

72
Q

Are signal sequences removed from the protein once it’s been sorted?

A

Often, but not always

73
Q

In the mitochondria, protein synthesis and folding occurs where

A

Cytosol

74
Q

Do the following phrases describe the import of proteins in the nucleus, mitochondria or both?

The imported protein encodes a nuclear localization signal

A

Nucleus

75
Q

The imported protein is pulled into the organelle’s lumen by chaperone proteins in…

A

Mitochondria

76
Q

Protein is first synthesized and folded in the cytosol before
being imported in….

A

Nucleus and mitochondria

77
Q

Important of proteins requires ATP in

A

Mitochondria

78
Q

Important of proteins requires GTP in

A

Nucleus

79
Q

Proteins are imported in their folded state in the

A

Nucleus

80
Q

Proteins are imported in their unfolded state in…

A

Mitochondria

81
Q

Where will a protein with an ER signal sequence be transported

A

Into the lumen of the ER

82
Q

Where will a protein with an ER signal sequence and a stop transfer sequence be transported

A

Into the membrane of ER then crosses the membrane 1 time

83
Q

Where will a protein with a start transfer sequence and a stop transfer sequence be transported

A

Embedded in the ER membrane and crosses the membrane twice

84
Q

Continual budding and fusion of ___ enables transport
from the ER to the Golgi apparatus, and from the Golgi to other
compartments

A

transport vesicles

85
Q

Vesicular transport allows

A

exocytosis and endocytosis

86
Q

What is the secretory pathway

A

ER to Golgi to cell surface

87
Q

Endocytic pathway

A

Plasma membrane to endosomes to lysosomes

88
Q

allows ingestion and degradation of extracellular molecules

A

Endocytosis

89
Q

Vesicular transport is

A

highly selective

90
Q

The formation of transport vesicles is energetically __

A

unfavorable

91
Q

__ is maintained during transport (i.e., the
cytosolic surface remains cytosolic; the extracellular/lumenal
surface remains extracellular/lumenal)

A

membrane topology

92
Q

Best-studied vesicles have a protein coat made of the protein

A

clathrin

93
Q

Clathrin molecules assemble into a basketlike network on the cytosolic side of the membrane, forming a

A

clathrin-coated pit

94
Q

Mechanism budding of a clathrin-coated vesicle

A
  1. Cargo receptors bind molecules selected for transport
  2. Adaptins capture cargo receptors and bind clathrin (forming coated pit)
  3. Dynamin assessmles as a ring and hydrolyzes GTP to help pinch off vesicles
  4. Following budding, the vesicle sheds its protein coat
95
Q

Uncoating of clathrin requires energy from

A

ATP hydrolysis

96
Q

Dynamin is a

A

GTPase

97
Q

__ on the vesicle surface are recognized by tethering
proteins on the target membrane

A

Rab proteins (GTPases)

98
Q

act as molecular markers for each membrane type

A

Rab proteins

99
Q

What ensures that transport vesicles fuse only with the correct membrane

A

Matching Rab and tethering protein

100
Q

what drives vesicle fusion

A

SNARE

101
Q

Movement between compartments is mediated by

A

transport vesicles

102
Q

Vesicle budding is driven by

A

protein coat assembly (clathrin, COP)

103
Q

Vesicle Scission is driven by assembly and

A

GTPase activity of Dynamin

104
Q

Fusion is driven by

A

v-SNARE/t-SNARE winding

105
Q

Rabs/tethering proteins provide

A

selective vesicle docking

106
Q

Most proteins are covalently modified in the

A

ER

107
Q

Disulfide bond formation is catalyzed by an

A

enzyme in the ER lumen

108
Q

help stabilize the structure of secreted proteins

A

Disulfide bonds

109
Q

Many proteins are glycosylated in the

A

ER

110
Q

Oligosaccharides linked to an asparagine side chain are are called

A

N-linked

111
Q

Subsequent modification of the oligosaccharide begins in the

A

ER

112
Q

A branched oligosaccharide containing 14 sugars is transferred from a lipid
(called dolichol) to the side chain of an

A

asparagine amino acid

113
Q

helps protect a protein from degradation by
preventing binding of proteases

A

Glycosylation

114
Q

can help mediate binding to chaperone proteins (ensuring quality control)

A

Glycosylation

115
Q

can serve as a transport signal for packaging the protein into an appropriate transport vesicle

A

Oligosaccharides

116
Q

Oligosaccharides on the cell surface can function in

A

cell-cell
recognition

117
Q

hold proteins in the ER until proper folding or assembly occurs

A

Chaperones

118
Q

If proper folding fails, the proteins are exported to the cytosol for degradation
in the

A

proteasome

119
Q

Misfolded proteins can accumulate in the ER, triggering the

A

unfolded protein response (UPR)

120
Q

If the ER cannot keep up with the demand, the UPR directs the cell to

A

apoptosis

121
Q

Golgi apparatus is a collection of flattened, membrane-enclosed sacs
called

A

cisternae

122
Q

Proteins and lipids travel in transport vesicles from the ER and fuse with
the

A

cis Golgi network

123
Q

Proteins exit the golgi from the

A

trans golgi network

124
Q

operates continually in all eukaryotic cells and
does not require a particular signal sequence

A

Constitutive exocytosis

125
Q

operates only in cells that are specialized for
secretion (i.e., secretory cells)

A

Regulated exocytosis

126
Q

common activator of regulated secretion

A

calcium

127
Q

Proteins destined for regulated
secretion…

A

aggregate with each other, packed onto high concentrations

128
Q

Secretory vesicles bud from the trans Golgi network and accumulate
near the

A

plasma membrane

129
Q

Influx of Ca2+ stimulates from pre-synpatic cell results in

A

fusion of synaptic vesicles

129
Q

Influx of Ca2+ stimulates from pre-synpatic cell results in

A

fusion of synaptic vesicles

130
Q

Ingestion of fluid and molecules via small pinocytic vesicles; carried out continually by all eukaryotic cells

A

Pinocytosis

131
Q

Ingestion of large particles; mainly carried out by phagocytic cells

A

Phagocytosis

132
Q

Ingested materials are delivered to

A

endosomes

133
Q

Material to be ingested is enclosed by the plasma membrane,
which buds inward to form an

A

endocytic vesicle

134
Q

Pseudopods fuse at their tips to form a

A

phagosomes

135
Q

phagosomes fuse to

A

lysosomes

136
Q

Pinocytosis is carried out mainly by

A

clathrin-coated pits and vesicles

137
Q

enables selection of macromolecules for ingestion via binding to complementary
receptors on the cell surface (e.g., transport of cholesterol/LDL)

A

Receptor-mediated endocytosis

138
Q

Empty receptors return either to their
original plasma membrane domain
(___) or to a different domain of
the plasma membrane
(___). Other receptors travel
to the lysosome for __.

A

recycling, transcytosis, degradation

139
Q

principal sites of intracellular digestion

A

lysosomes

140
Q

Lysosomes contain ~40 types of

A

hydrolytic enzymes active in lumen

141
Q

Enzymes and membrane proteins of the lysosome are synthesized in the

A

ER

142
Q

A phosphorylated sugar group,___, is added to these proteins while they are in the cis Golgi network.

A

mannose 6-phosphate

143
Q

This sugar is recognized by the mannose 6-phosphate receptor, enabling sorting
into transport vesicles for

A

delivery to lysosomes via endosomes

144
Q

is used to degrade obsolete parts of the cell (like organelles) via the
formation of a double membrane around the material to be ingested

A

autophagy

145
Q

Transmembrane protein that binds molecules selected for transport

A

Cargo receptor

146
Q

Assembles as a ring around the neck of a clathrin-coated pit

A

Dynamin

147
Q

GTPase that acts as a marker on the surface of transport Rab vesicles and is recognized by tethering proteins on the target membrane

A

Rab

148
Q

Pairs of these proteins wind around one another, pulling the vesicle’s membrane close to the target membrane and promoting fusion

A

SNARE

149
Q

protein that captures cargo receptors and secures the
clathrin coat to the vesicle membrane

A

Adaptin

150
Q

Assembles into a basketlike network that gives budding
vesicles their shape

A

Clathrin

151
Q

True or false

____Early endosomes mature into late endosomes as they fuse with each other or with pre-existing late endosomes.

_______The interior of an endosome is kept basic (pH 8-9) by an ATP- driven proton pump located in the endosomal membrane.

_______ Endocytic cargo that dissociates from its receptor in the endosome is destined for degradation in the lysosome.

_______ Proteins destined for the plasma membrane are tagged with mannose-6-phosphate.

_______ After pinching off from the plasma membrane, clathrin-coated vesicles shed their coat and fuse with the Golgi apparatus.

A

T
F
T
F
F

Cell Bio (15 decks)

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