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Cell Bio - Exam 2

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Test sobre Cell Bio - Exam 2, creado por Ryan Pappal el 19/10/2014.
Ryan Pappal
Test por Ryan Pappal, actualizado hace más de 1 año
Ryan Pappal
Creado por Ryan Pappal hace más de 9 años
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Pregunta 1

Pregunta
Post-translational translocation of non-secretory proteins across membranes could occur in which organelles?
Respuesta
  • mitochondria
  • chloroplasts
  • nuclei
  • Golgi
  • ER
  • peroxisomes
  • lysosomes

Pregunta 2

Pregunta
Select the correct sequential steps for cotranslational translocation (signal hypothesis):
Respuesta
  • ER signal sequence is translated at free ribosome
  • Sequence allows ribosome to bind to a translocator on RER
  • Pore is formed and polypeptide is translated through to the RER lumen
  • Signal peptidase cleaves signal sequence
  • Protein is released into the ER lumen

Pregunta 3

Pregunta
The discovery of cotranslational translocation involved:
Respuesta
  • Secretory proteins translated in vitro were smaller than those in vivo. Microsomes from ER added to in vitro proteins resulted in larger size.
  • Secretory proteins were the same size in vitro and in vivo.
  • Secretory proteins translated in vitro were larger than those in vivo. Microsomes from ER added to in vitro proteins resulted in correct size.

Pregunta 4

Pregunta
Signal sequences:
Respuesta
  • vary greatly but have 6+ hydrophobic aa string at N terminus
  • vary greatly but have 8+ hydrophobic aa string at N terminus
  • vary greatly but have 6+ hydrophobic aa string at C terminus
  • vary greatly but have 8+ hydrophobic aa string at C terminus

Pregunta 5

Pregunta
Signal recognition particle can bind to signal sequences of multiple shapes and sizes because:
Respuesta
  • Hydrophilic pocket lined with methionine, which has inflexible side chains.
  • Hydrophobic pocket lined with methionine, which has flexible side chains.
  • Hydrophobic pocket lined with methionine, which has inflexible side chains.

Pregunta 6

Pregunta
Select the steps for SRP function:
Respuesta
  • SRP binds to small ribosomal subunit
  • SRP binds to large ribosomal subunit.
  • Binding pocket fits around nascent chain exit site and binds to ER signal sequence.
  • Translational pause domain positions at interface between ribosomal subunits.
  • SRP binds to SRP-R.
  • Mechanism possibly related to GDP binding sites near SRP-R.
  • SRP released, translation continues embedded in ER.
  • ER signal sequence binds to hydrophobic site on inside of locator, opening the channel.
  • Polypeptide extruded into ER, peptidase cleaves signal.

Pregunta 7

Pregunta
ER signal sequence is checked:
Respuesta
  • One time. SRP.
  • Two times. SRP, SRP-R.
  • Three times. SRP, SRP-R, signal peptidase.

Pregunta 8

Pregunta
Translocator for secreted proteins in ER is called:
Respuesta
  • Sec 59.
  • Sec 51.
  • Sec 61.
  • Sec 63.

Pregunta 9

Pregunta
Sec 61 has opening in side for:
Respuesta
  • Integration of TMDs.
  • Cleaved signal sequence to diffuse into membrane.
  • Ribosome to insert peptide from side.
  • Hydrophobic influence in Sec 61 pore.

Pregunta 10

Pregunta
A type I TMD has:
Respuesta
  • N terminus in ER lumen.
  • C terminus in ER lumen.

Pregunta 11

Pregunta
A type II TMD has:
Respuesta
  • N terminus in ER lumen.
  • C terminus in ER lumen.

Pregunta 12

Pregunta
For 1 pass TMDs, orientation is determined by:
Respuesta
  • Location of (+) charge, always goes to cytosol
  • Location of (+) charge, always goes to ER lumen
  • Location of 3 aa repeat, always goes to cytosol
  • Location of 3 aa repeat, always goes to ER lumen

Pregunta 13

Pregunta
In two TMD insertion, the signal is cleaved.
Respuesta
  • True
  • False

Pregunta 14

Pregunta
In multiple TMD insertion:
Respuesta
  • There is an internal start-transfer sequence and C-terminus stop-transfer sequence.
  • There is an N-terminus start-transfer sequence and a C-terminus stop-transfer sequence.
  • There is an internal start-transfer sequence and internal stop-transfer sequence.
  • There is an N-terminus start-transfer sequence and an internal stop-transfer sequence.

Pregunta 15

Pregunta
Many ER resident proteins stay in the ER because:
Respuesta
  • They have an ER retention signal.
  • They are too small to be absorbed into vesicles.
  • They are anchored on a special receptor called ER-R.

Pregunta 16

Pregunta
PDI is:
Respuesta
  • Protein disulfide isomerase.
  • Protein disulfur isomerase.
  • Protein disulfide isomerate.
  • Protein disulfur isomerate.

Pregunta 17

Pregunta
PDI's function is:
Respuesta
  • Formation of disulfide bonds between sulfhydryls of cysteins.
  • Formation of disulfide bonds between sulfhydryls of nucleotides.
  • Binding to unfolded proteins to prevent aggregation.
  • Binding to unfolded proteins to facilitate aggregation.

Pregunta 18

Pregunta
BiP is:
Respuesta
  • Binding Protein.
  • Binder Protein.
  • Binding in Protein.

Pregunta 19

Pregunta
BiP functions by:
Respuesta
  • Binding to unfolded proteins and preventing aggregation.
  • Binding to unfolded proteins and promoting aggregation.
  • Forming disulfide bonds between sulfhydryls of cysteins.
  • Forming disulfide bonds between sulfhydryls of nucleotides.

Pregunta 20

Pregunta
BiP and PDI aid in:
Respuesta
  • Secretory pathway in the Golgi.
  • Secretory pathway in the ER.
  • Proper folding of proteins.
  • Aggregation of proteins.

Pregunta 21

Pregunta
Glycosylation aids in:
Respuesta
  • Folding proteins.
  • Protecting against degradation.
  • Cell communication.
  • Sorting.

Pregunta 22

Pregunta
Which is more common at 90%?
Respuesta
  • N-linked glycosylation.
  • O-linked glycosylation.

Pregunta 23

Pregunta
N-linked glycosylation occurs by attaching sugar residues to:
Respuesta
  • Amide nitrogen of asparagine.
  • Amide nitrogen of cysteine.
  • Amide nitrogen of serine.

Pregunta 24

Pregunta
OST is:
Respuesta
  • oligosaccharyl transferase.
  • oligosaccglycol transferase.
  • oligoseryl transferase.

Pregunta 25

Pregunta
OST transfers what structure to the target side chain during N-linked glycosylation?
Respuesta
  • 14 sugar compound of GlcNAc, mannose, glucose.
  • 14 sugar compound of GlcNAc, mannose.
  • 16 sugar compound of GlcNAc, mannose, glucose.
  • 16 sugar compound of GlcNAc, mannose.

Pregunta 26

Pregunta
OST glycosylates:
Respuesta
  • All asparagines.
  • Only asparagines within a specific sequence (Asn - X - Ser/Thr).

Pregunta 27

Pregunta
Initial sugars that form the basis of all N-linked glycosylations are:
Respuesta
  • 2 GlcNAc, 3 Man
  • 3 GlcNAc, 2 Man
  • 2 Glu, 3 GlcNAc
  • 3 Glu, 2 GlcNAc
  • 2 Man, 3 Glu
  • 3 Man, 2 Glu

Pregunta 28

Pregunta
OST aids in glycosylation of cytosolic proteins.
Respuesta
  • True
  • False

Pregunta 29

Pregunta
Dolichol:
Respuesta
  • Holds sugar structure awaiting transfer by OST.
  • Builds sugar structure awaiting transfer by OST.
  • Facilitates ATP hydrolysis of OST.
  • Holds energy for sugar transfer in pyrophosphate bond.
  • Uses ATP to transfer sugar.
  • Uses GTP to transfer sugar.

Pregunta 30

Pregunta
OST:
Respuesta
  • Is associated with every Sec 61 translocator and each has a dolichol anchor nearby.
  • Is associated with some Sec 61 translocators and each has a dolichol anchor nearby.
  • Is associated with all Sec 61 translocators but not dolichols.

Pregunta 31

Pregunta
OST catalyzes the addition of sugar groups:
Respuesta
  • During translation of the target protein.
  • After the signal peptide is cleaved.
  • The instant translation finishes.

Pregunta 32

Pregunta
Which sugar combination is associated with entrance into the Golgi?
Respuesta
  • 8 Man, 2 GlcNAc
  • 6 Man, 2 GlcNAc
  • 2 Man, 8 GlcNAc
  • 2 Man, 6 GlcNAc

Pregunta 33

Pregunta
O-linked glycosylation:
Respuesta
  • Makes up about 90% of glycosylation events.
  • Makes up about 10% of glycosylation events.
  • Involves attachment of sugar to hydroxyl group of serine.
  • Involves attachment of sugar to hydroxyl group of threonine.

Pregunta 34

Pregunta
Synthesis of precursor oligosaccharide begins:
Respuesta
  • In membrane layer.
  • Cytosolic face.
  • ER lumen face.

Pregunta 35

Pregunta
Dolichol:
Respuesta
  • Is very hydrophobic, spans bilayer 3+ times.
  • Is very hydrophilic, spans bilayer 3+ times.
  • Is very hydrophobic, spans bilayer 2 times.
  • Is very hydrophilic, spans bilayer 2 times.

Pregunta 36

Pregunta
Synthesis on dolichol:
Respuesta
  • Is en bloc.
  • Is one sugar at a time.

Pregunta 37

Pregunta
Dolichol's pyrophosphate bond is located:
Respuesta
  • In the membrane.
  • Within dolichol.
  • Between dolichol and the sugar group.
  • In the sugar group.
  • On the end of the sugar group.

Pregunta 38

Pregunta
During flip of dolichol, (Glc)3(Man)9(GlcNAc)2 turns into (GlcNAc)2(Man)5.
Respuesta
  • True
  • False

Pregunta 39

Pregunta
ER chaperones require:
Respuesta
  • K+
  • Ca2+
  • H+
  • Mg2+

Pregunta 40

Pregunta
Calnexin & calreticulin:
Respuesta
  • Prevent unproperly folded proteins from leaving the ER.
  • Keep ER resident proteins critical for proper folding inside the ER.
  • Are the only proteins needed for proper management of proteins in the ER.

Pregunta 41

Pregunta
Calnexin is membrane bound.
Respuesta
  • True
  • False

Pregunta 42

Pregunta
Calreticulin is membrane bound.
Respuesta
  • True
  • False

Pregunta 43

Pregunta
Select the proper steps for calnexin function:
Respuesta
  • Calnexin recognizes a single glucose after glucose trimming.
  • Calnexin recognizes a double glucose after glucose trimming.
  • ER resident glucosidase removes final glucose(s) off of protein.
  • Calreticulin recognizes absence of glucose and binds.
  • If proper folding occurs, protein is bound by glucosyl transferase.
  • Inproperly folded proteins have sugars added back onto their N-linked oligo to go back through cycle.

Pregunta 44

Pregunta
If proper folding fails:
Respuesta
  • Protein goes through retrotranslocation.
  • Protein possibly goes back through Sec61.
  • N-glycanase removes oligosaccharide chains en bloc in ER.
  • Oligosaccharide chains removed in cytosol.
  • Ubiquitin marks proteins for degradation by recognizing certain sequences that should not be exposed in properly-folded proteins.
  • Lysosome breaks down ubiquitin-marked proteins.
  • Proteaomse processes ubiquitin-marked proteins.

Pregunta 45

Pregunta
Consider proteins that take too long to fold:
Respuesta
  • They are processed in the same manner as proteins that are incorrectly folded once recognized.
  • They have an organic timer mediated by mannosidase.
  • Calnexin cycle resets the mannose timer.
  • Proteins that fold properly keep all their mannoses.

Pregunta 46

Pregunta
Unfolded protein response involves:
Respuesta
  • Accumulation of unfolded proteins in ER.
  • Activation by high proteasome activity.
  • Increased transcription of genes involving ER chaperones, retrotranslocation proteins, protein-folding proteins.
  • Involve IRE1.

Pregunta 47

Pregunta
IRE1:
Respuesta
  • is a transmembrane protein kinase.
  • is an ER chaperone catalyst.
  • autophosphorylates.
  • dimerizes.
  • trimerizes.
  • has endoribonuclease domain that edits a specific mRNA in cytosol.
  • affects activation of genes in nucleus through mRNA editing.
  • enters the nucleus after signaling to affect gene transcription.

Pregunta 48

Pregunta
____ controls coat assembly.
Respuesta
  • GTP binding protein.
  • Sar1.
  • Sec61.
  • ATP binding protein.
  • ATPase.

Pregunta 49

Pregunta
GEF is:
Respuesta
  • guanine nucleotide exchange factor.
  • guanine export factor.

Pregunta 50

Pregunta
Sar1 is associated with COPI vesicles.
Respuesta
  • True
  • False

Pregunta 51

Pregunta
Sec12:
Respuesta
  • is an ER membrane protein.
  • is a cytosolic protein.
  • is a type of GEF.
  • binds Sar1-GDP and catalyzes release of GDP and binding of GTP.
  • binds Sar1-GTP and catalyzes hydrolysation and subsequent release of GDP.
  • is involved with COPI vesicles.
  • is involved with COPII vesicles.

Pregunta 52

Pregunta
Select the correct steps for COPII coat assembly:
Respuesta
  • Sar1-GTP serves as a binding site for Sec23 & 24.
  • Sec23 & 24 select cargo.
  • Sec13 & 31 proteins form second layer to COPII structure.
  • Sec16 increases coat polymerization efficacy.
  • Sec17 increases coat polymerization efficacy.
  • Sec23 promotes GTP hydrolysis of Sar1-ATP.
  • Sec23 promotes GTP hydrolysis of Sar1-GTP.
  • Sar1-GDP is released from vesicle membrane, allowing coat to rapidly dissemble.
  • t-SNARE is exposed on surface, allowing fusing process to begin.
  • v-SNARE is exposed on surface, allowing fusing process to begin.

Pregunta 53

Pregunta
Rab-GDP is active in the cytosol.
Respuesta
  • True
  • False

Pregunta 54

Pregunta
Rab-GTP is free in the cytosol.
Respuesta
  • True
  • False

Pregunta 55

Pregunta
Select the correct steps for vesicle fusion:
Respuesta
  • Vesicle binding is mediated by Rab GTPase.
  • Cytosolic Rab-GDP converted to Rab-GTP by GEF.
  • Rab-GTP binds to Rab effector on target membrane.
  • t-SNARE and v-SNARE become close enough to interact and "hook."
  • NSF with an alpha-SNAP binds the SNAREs.
  • NSF catalyzes hydrolysis of ATP, forming energy needed to dissociate SNARE complexes.
  • Rab protein hydrolyzes its bound GTP releasing Rab effector.
  • Rab-GDP is released into cytosol for next cycle.

Pregunta 56

Pregunta
Studies with VSVG-GFP revealed:
Respuesta
  • Some vesicles detached from the ER directly fused with the Golgi if the travel distance was short.
  • COPII vesicles traveled toward the Golgi when originally thought COPII did retrograde transport back to the ER.
  • If Golgi was several micrometers away, vesicles en route to Golgi fused prior to Golgi contact, forming cis-Golgi network.
  • Retrograde vesicles budded off the Golgi toward the ER.
  • trans-Golgi network formed after trans-Golgi pushed out of Golgi from cisternal maturation.

Pregunta 57

Pregunta
Purpose of retrograde transport to ER:
Respuesta
  • Return t-SNARE.
  • Return v-SNARE.
  • Return membrane to ER.
  • Retrieve ER resident proteins.
  • Bring proteins back for new modifications before packaging to PM.

Pregunta 58

Pregunta
Retrograde transport to ER from Golgi involves COPI while retrograde transport from Golgi to Golgi involves COPII.
Respuesta
  • True
  • False

Pregunta 59

Pregunta
COPI coat proteins are composed of:
Respuesta
  • 6 large cytosolic polypeptide complexes (coatomers).
  • 4 large cytosolic polypeptide complexes (coatomers).
  • Coatomers with alpha and beta subunits.
  • Whole coatomers, no subunits.

Pregunta 60

Pregunta
COPI vesicles are controlled by:
Respuesta
  • Sec12, a GEF.
  • ARF (ADP ribosylation factor).
  • Sar1, a GTP-binding factor.

Pregunta 61

Pregunta
Select the proper steps for COPI formation:
Respuesta
  • ARF-GDP is weakly tethered to the Golgi membrane by a weak covalent protein mod on N-terminus.
  • ARF-GTP is strongly tethered to the Golgi membrane by a strong covalent protein mod on N-terminus.
  • GEF on Golgi catalyzes formation of ARF-GTP. ARF now strongly tethered to Golgi membrane.
  • Tight association of ARF-GTP serves as foundation for coatomer formation on COPI vesicles.
  • Coat dissembles and Rab mediates binding to target membrane.
  • SNARES facilitate fusion to target membrane.

Pregunta 62

Pregunta
Yeast COPI mutants showed protein accumulation in ER. This was because...
Respuesta
  • Mutant COPI vesicles lacked the ability to perform vesicle transport of proteins to the Golgi apparatus.
  • Mutant COPI vesicles successfully formed vesicles, but the mutation made them immediately fuse back with the ER so transport did not occur.
  • Mutant COPI vesicles could not bring back proteins necessary for anterograde transport to continue.
  • Mutant COPI vesicles fused readily with COPII vesicles, interrupting the transport chain.

Pregunta 63

Pregunta
Because ER resident proteins are so abundant...
Respuesta
  • They easily get trapped in outgoing vesicles.
  • Retrograde transport is necessary to maintain presence of ER resident proteins in the ER.
  • Specialized receptors prevent ER resident proteins from getting entrapped in outgoing vesicles.
  • ER resident proteins are mostly free in the ER lumen, so outgoing vesicles usually do not trap ER resident proteins, and the cell can replace readily those that do.

Pregunta 64

Pregunta
Soluble ER resident proteins are targeted back to the ER...
Respuesta
  • By an ER retention signal (KDEL) that passes directly to the membrane, causing a COPI vesicle to form.
  • By an ER retention signal (KDEL) that binds to a special KDEL Receptor in low pHs, allowing retrograde transport.
  • By an ER retention signal (KDEL) that binds to a special KDEL Receptor in high pHs, allowing retrograde transport.
  • By an ER retention signal (KDEL) that binds to KDEL Receptor on COPII vesicles, essentially redirecting the vesicle to the ER before fusion with the Golgi.

Pregunta 65

Pregunta
What special signal targets KDEL receptor back to the ER?
Respuesta
  • KKXX signal on C terminus.
  • KKXX signal on N terminus.
  • KDEL signal on C terminus.
  • KDEL signal on N terminus.
  • 3 Man, 2 Glu on C terminus.
  • 3 Man, 2 Glu on N terminus.

Pregunta 66

Pregunta
KDEL Receptor binds to KDEL to:
Respuesta
  • Take back ER resident proteins.
  • Forward modified proteins to the next part of the Golgi.

Pregunta 67

Pregunta
KDEL binds at:
Respuesta
  • low pH.
  • high pH.

Pregunta 68

Pregunta
KDEL is released from KDEL-R at:
Respuesta
  • low pH.
  • high pH.

Pregunta 69

Pregunta
ER has a ____ pH compared to the Golgi.
Respuesta
  • lower
  • higher

Pregunta 70

Pregunta
KKXX binds to:
Respuesta
  • outer phospholipids of COPI vesicles.
  • alpha and beta subunits of COPI vesicles.
  • special KDEL-R receptor on COPI vesicles.
  • KDEL-R.

Pregunta 71

Pregunta
It's been observed that yeast mutants that lack COPI alpha and beta subunits:
Respuesta
  • still have successful retrograde transport of KDEL-signal proteins.
  • have proteins that need to be transported back to the ER remaining in the Golgi.
  • send KDEL-marked proteins to lysosomes.
  • lack the problem of having ER-resident proteins being erroneously sent to the Golgi.

Pregunta 72

Pregunta
Forward movement of proteins through the Golgi involves vesicles.
Respuesta
  • True
  • False

Pregunta 73

Pregunta
Backward movement of Golgi enzymes involves vesicles.
Respuesta
  • True
  • False

Pregunta 74

Pregunta
In cisternal maturation, trans becomes medial and medial becomes cis.
Respuesta
  • True
  • False

Pregunta 75

Pregunta
Scale-covered algae:
Respuesta
  • had cell-wall glycoproteins assembled in the Golgi that were 20X larger than any observed vesicle.
  • had cell-wall glycoproteins that were small enough to fit inside vesicles.
  • had cell-wall glycoproteins that were about as large as vesicles, spurring additional research into cisternal maturation.

Pregunta 76

Pregunta
Collagen synthesis by fibroblasts:
Respuesta
  • involves precollagen, a precusor too large for vesicles.
  • involves precollagen aggregates, which have never been seen in vesicles.
  • provides evidence for cisternal maturation.
  • provides evidence for anterograde vesicular transport in the Golgi.
  • provides evidence that retrograde Golgi transport of enzymes occurs.
  • involves trimming of precollagen, the pieces of which are transported backwards via vesicles in the Golgi.
  • involves COPII vesicles to bring enzymes in the Golgi forward as cisternal maturation occurs.

Pregunta 77

Pregunta
Enzymes move retrograde in the Golgi via:
Respuesta
  • COPI vesicles.
  • COPII vesicles.
  • They don't. They move back in the same compartment via cisternal maturation.

Pregunta 78

Pregunta
The Golgi does what to secreted proteins during processing?
Respuesta
  • en bloc modifications to the oligosaccharides, where a protein's modification is processed separately and one exchange occurs before exportation.
  • sequential modifications to the oligosaccharides, where each product is another enzyme's substrate.
  • varies different proteins' oligosaccharides.
  • uniforms different proteins' oligosaccharides.

Pregunta 79

Pregunta
A soluble protein sent to the Golgi can only be secreted.
Respuesta
  • True
  • False

Pregunta 80

Pregunta
Select the correct steps for processing of lysosomal enzymes by the Golgi:
Respuesta
  • Lysosomal proteins come to the Golgi with (Man)8(GlcNAc)2 oligosaccharide.
  • Lysosomal proteins come to the Golgi with (Man)3(GlcNAc)2 oligosaccharide.
  • 2 cis Golgi residents form the M6P.
  • 2 medial Golgi residents form the M6P.
  • M6P is an oligosaccharide.
  • N-acetylglucosamine phosphotransferase binds to lysosomal protein signal.
  • N-acetylglucosamine phosphotransferase catalyzes addition of phosphorylated GlcNAc group to carbon 6 of mannose on enzyme oligosaccharide.
  • GlcNAc phosphotransferase can mistakenly add M6P to secretory proteins.
  • Phosphodiesterase removes GlcNAc, leaving a phosphate.
  • Phosphodiesterase removes phosphate, leaving the oligosaccharide.

Pregunta 81

Pregunta
Select the possible destinations of proteins from the t-Golgi network.
Respuesta
  • PM via constitutive secretion.
  • PM via selective secretion.
  • PM via regulated secretion.
  • Lysosome via late endosome.
  • Lysosome directly.
  • PM directly.
  • ER via retrograde transport.
  • ER directly.

Pregunta 82

Pregunta
Regulated secretion:
Respuesta
  • involves release of a protein after a stimulus.
  • involves constant and direct secretion of a protein.
  • involves storing a protein in a vesicle for long term storage.
  • involves sending a protein directly to the PM.
  • involves nothing.

Pregunta 83

Pregunta
During protein-storing vesicle formation:
Respuesta
  • Proteins in vesicles from t-Golgi network aggregate before fusing with the target storage vesicle.
  • Proteins in vesicles fuse directly to the target storage vesicle without aggregation.

Pregunta 84

Pregunta
Studies show mammalian secretory cells contain:
Respuesta
  • Chromogranin.
  • Chromogranin A.
  • Chromogranin B.
  • Chromogranin I.
  • Chromogranin II.

Pregunta 85

Pregunta
The Chromogranin proteins in mammalian cells
Respuesta
  • aggregate only in storage vesicles.
  • aggregate in the t-Golgi network, but only with a pH of 6.5 and 1mM Ca2+.
  • aggregate in the t-Golgi network, but only with a pH of 5.5 and 1mM Ca2+.
  • may be basis for sorting secretory proteins either into regulated or constitutive secretion.
  • is not involved in sorting secretory proteins into regulated or constitutive secretion.

Pregunta 86

Pregunta
Proteins that do not associate with a Chromogranin aggregation:
Respuesta
  • will not be secreted.
  • will only be secreted from a storage vesicle.
  • will be carried to the PM for constitutive secretion.
  • Chromogranin aggregations do not bind with secretory proteins.

Pregunta 87

Pregunta
Proproteins of constitutive secreted proteins:
Respuesta
  • undergo proteolytic cleavage to form a mature, active protein.
  • undergo proteolytic cleavage in the t-Golgi network.
  • in mammalian cells are probably processed by furin.
  • in mammalian cells are probably processed by endoprotease PC2.
  • are cleaved once, at C-terminal dibasic sequence.
  • are cleaved once, at N-terminal dibasic sequence.

Pregunta 88

Pregunta
PC2 and PC3
Respuesta
  • are exoproteases.
  • act on proproteins for constitutive secreted proteins.
  • can help form insulin from proinsulin.

Pregunta 89

Pregunta
Insulin:
Respuesta
  • is cleaved to form N-terminal B chain and C-terminal A chain connected by disulfide bonds.
  • is a constitutive secreted protein.
  • probably has processing done by carboxypeptidase, which removes 2 basic aa residues.

Pregunta 90

Pregunta
Proteolytic processing is common because
Respuesta
  • keeps harmful enzymes from acting anywhere except its target organelle.
  • Peptides that are too large need to be contained in proproteins.
  • ex. enkephalins would not be synthesizable without proteolytic processing.

Pregunta 91

Pregunta
SNARE complex is stable because:
Respuesta
  • long alpha helices that coil to form a four alpha helix bundle.
  • long alpha helices that coil to form a two alpha helix bundle.
  • Hydrophobic residues at central core.
  • Hydrophilic residues at central core.
  • Alignment of aas of opposite charge forming favorable electrostatic interaction.

Pregunta 92

Pregunta
Clathrin:
Respuesta
  • mediates COPI and COPII vesicles.
  • mediates lysosomal enzyme transport vesicles.
  • are diskelions.
  • have three limbs.
  • polymerize to form polygonal lattice.
  • associates with AP complexes when monomer.
  • associates with AP complexes when polymerized.

Pregunta 93

Pregunta
Type of APs:
Respuesta
  • AP1, helps with t-Golgi network to endosome transport.
  • AP1, helps with PM to endosome transport.
  • AP2, helps with PM to endosome transport.
  • AP2, helps with endosome to t-Golgi network transport.
  • AP3, helps with t-Golgi network to lysosome transport.
  • AP3, helps with t-Golgi network to endosome transport.

Pregunta 94

Pregunta
AP1 interacts with:
Respuesta
  • KDEL.
  • KKXX.
  • YXXo.
  • DXLL.
  • DFGXo.

Pregunta 95

Pregunta
GGA is:
Respuesta
  • a new type of AP.
  • AP1.
  • AP2.
  • AP3.
  • a clathrin GTPase.

Pregunta 96

Pregunta
AP3:
Respuesta
  • can help deliver proteins to melanosomes in skin cells.
  • can help mediate protein transport to specialized compartments.
  • may not need clathrin for its vesicles to function.
  • helps vesicles bypass the late endosome.

Pregunta 97

Pregunta
GGA interacts with:
Respuesta
  • YXXo.
  • DXLL.
  • DFGXo.
  • Sec61.

Pregunta 98

Pregunta
Clathrin is needed for GGA vesicles.
Respuesta
  • True
  • False

Pregunta 99

Pregunta
All lysosomal vesicles utilize ARF GTPase to initiate coat assembly.
Respuesta
  • True
  • False

Pregunta 100

Pregunta
Dynamin is necessary for Clathrin coated vesicles to form.
Respuesta
  • True
  • False

Pregunta 101

Pregunta
Dynamin polymerizes around the neck of the vesicle bud and hydrolyzes ATP.
Respuesta
  • True
  • False

Pregunta 102

Pregunta
Dynamin:
Respuesta
  • hydrolyzes ATP.
  • hydrolyzes GTP.
  • helps COPI and COPII vesicles form.
  • works via conformational change that pinches vesicles.

Pregunta 103

Pregunta
Hsc70:
Respuesta
  • is a constitutive expressed molecular chaperone.
  • does not exist.
  • uses ATP hydrolysis.
  • uses GTP hydrolysis.
  • allows v-SNARE exposure and binding via Rab effector action.
  • allows t-SNARE exposure.

Pregunta 104

Pregunta
ARF hydrolyzes to have conformational change that regulates timing of clathrin depolymerization.
Respuesta
  • True
  • False

Pregunta 105

Pregunta
Select correct steps for transport of lysosomal enzymes to the lysosome:
Respuesta
  • M6P receptor binds in TGN.
  • pH must be 5.5 for M6P receptor to function.
  • ARF allows for coat assembly.
  • M6P receptor has YXXF.
  • M6P receptor has YXXo.
  • Dynamin does its thang.
  • Vesicle is uncoated via Hsc70.
  • Rab-GTP binds with Rab effector to facilitate SNARE interactions.
  • M6P receptor dissociates at lysosomal pH, and a phosphatase breaks up M6P.
  • Some M6P is then transferred to cell surface.

Pregunta 106

Pregunta
M6P is present at cell surface:
Respuesta
  • because it is sent there from the ER.
  • to release lysosomal enzymes into the ECM.
  • to retrieve lysosomal enzymes that were missorted.

Pregunta 107

Pregunta
Microphages can ingest:
Respuesta
  • 25% of own volume per hour.
  • 5% of PM per minute.

Pregunta 108

Pregunta
Phagocytosis:
Respuesta
  • is actin-mediated.
  • involves pseudopodia that surround target particle.
  • requires substances to transmit signals to inside of the cell.
  • is used by almost all cell types.

Pregunta 109

Pregunta
Fab regions:
Respuesta
  • recognize and bind infection organisms.
  • aid in pseudopodia development.
  • bind to other cells to mark as friendly.

Pregunta 110

Pregunta
Fc receptors allow phagocytic immune cells to target cells marked by Fab.
Respuesta
  • True
  • False

Pregunta 111

Pregunta
Receptor-mediated endocytosis:
Respuesta
  • involves clathrin-coated pits.
  • mostly utilizes AP1.
  • mostly utilizes AP2.
  • mostly utilizes AP3.
  • requires GTP hydrolysis to occur.
  • requires that receptors be recycled.
  • involves receptors that are freshly made from the Golgi.

Pregunta 112

Pregunta
The rate-limiting step of ligand internalization is:
Respuesta
  • number of receptors.
  • GTP concentration.
  • ATP concentration.
  • clathrin abundancy.

Pregunta 113

Pregunta
Ligands for receptor-mediated endocytosis include:
Respuesta
  • H2O
  • cholesterol carriers
  • erroneously sorted lysosomal proteins
  • protein hormones
  • transferrin
  • iron-binding proteins

Pregunta 114

Pregunta
Functions of cholesterol include:
Respuesta
  • maintain membrane fluidity.
  • fatty acid conversion.
  • synthesis of steroids.
  • killing heart tissue.

Pregunta 115

Pregunta
Water-soluble carriers for lipids called:
Respuesta
  • lipoproteins.
  • lipocholesterols.
  • lipocarriers.
  • McDonald's.

Pregunta 116

Pregunta
HDLs contain:
Respuesta
  • high levels of protein.
  • high levels of lipids.
  • high levels of cholesterol.

Pregunta 117

Pregunta
LDLs contain more ___ relative to HDLs.
Respuesta
  • proteins.
  • fats.
  • cholesterol.

Pregunta 118

Pregunta
Shell of LDL/HDLs composed of:
Respuesta
  • apolipoproteins.
  • polioproteins.
  • cholesterol-containing phospholipid monolayer.
  • cholesterol-containing phospholipid bilayer.
  • cholesterol-containing phospholipid trilayer.

Pregunta 119

Pregunta
LDL/HDL shell is amphipathic because:
Respuesta
  • outer hydrophilic surface.
  • inner hydrophilic surface.
  • outer hydrophobic surface.
  • inner hydrophobic surface.

Pregunta 120

Pregunta
LDL:
Respuesta
  • is the major cholesterol carrier.
  • carries more cholesterol than HDL.
  • has hydrophobic core with about 1500 esterified chol. molecules.
  • has only one apolipoprotein called apoA-100.

Pregunta 121

Pregunta
LDL-R:
Respuesta
  • has one TMD.
  • has two TMDs.
  • has long terminal N exoplasmic segment with ligand binding arm.
  • has long terminal C exoplasmic segment with ligand binding arm.
  • has binding arm with 7 cysteine-rich repeats of 40aa each.
  • has binding arm with 5 cysteine-rich repeats of 30aa each.
  • has YXXP signal.
  • has NPXY signal.
  • binds to AP-1.
  • binds to AP-2.

Pregunta 122

Pregunta
Select proper steps for LDL intake:
Respuesta
  • Neutral pH of cell surface allows apoB binding to LDL-R binding arm.
  • NPXY signal grabs AP-1 to form clathrin coat.
  • NPXY signal grabs AP-2 to form clathrin coat.
  • Dynamin hydrolyses GTP to pinch off vesicle.
  • Vesicle is shed with Hsc70's help. ARF-GTP to ARF-GDP.
  • Rab interaction allows for SNARE complex formation at pH of 5 at endosome.
  • At acidic endosome, histidine on LDL-R beta-propeller becomes (+).
  • Ligand binding arm now binds to LDL-R beta propeller.
  • LDL is released.

Pregunta 123

Pregunta
In lysosome, LDL:
Respuesta
  • has apoB hydrolyzed by protease.
  • has cholesterol esters exposed to cholestryl esterases.

Pregunta 124

Pregunta
Microvilli are composed of:
Respuesta
  • actin
  • MTs
  • intermediate filaments

Pregunta 125

Pregunta
Aggregations of small soluble subunits of cytoskeleton fibers are:
Respuesta
  • polymers.
  • protofilaments.
  • complete structures.
  • monomers.
  • dimers.
  • held together by strong covalent bonds, allowing for strength of the cytoskeleton.
  • held together by weak non-covalent bonds, allowing flexibility.

Pregunta 126

Pregunta
Protofilaments:
Respuesta
  • must avoid breaking from mere thermal motion.
  • form lateral connections with adjacent protofilaments.
  • assemble/disassemble only at the ends.
  • can assemble/disassemble in the middle.
  • of intermediate filaments form alpha helix coiled coils.
  • of actin and MTs are formed from globular monomers.

Pregunta 127

Pregunta
Microfilaments:
Respuesta
  • are the thinnest structures.
  • measure at 7 nm in width.
  • support the shape of the cell.
  • are made of actin monomers that form 3 chains that twist around each other.

Pregunta 128

Pregunta
G-actin:
Respuesta
  • has ATP binding site in cleft (facing (-) end) in center.
  • has a distinct polarity +/-.
  • has polarity due to electroactive aa side chains.

Pregunta 129

Pregunta
The plus end of an actin subunit polymer:
Respuesta
  • is positively charged.
  • is barbed.
  • is pointed.
  • breaks down and builds up rapidly.
  • changes rather slowly.

Pregunta 130

Pregunta
A lag is seen at the beginning of actin subunit interaction because:
Respuesta
  • nucleation must occur, which is a slow process.
  • subunits at the plus end are competing for space.
  • ATP hydrolysis takes time to occur.

Pregunta 131

Pregunta
Adding a nucleated actin segment:
Respuesta
  • worsens lag time.
  • eliminates lag time.
  • doesn't have an effect.

Pregunta 132

Pregunta
Catalysts of nucleation:
Respuesta
  • allow nucleation to occur quicker.
  • allow structures to build anywhere.
  • target structures to areas needed by the cell.

Pregunta 133

Pregunta
Actin nucleation is often regulated:
Respuesta
  • by external signals.
  • by genes.
  • by evil scientists.

Pregunta 134

Pregunta
Nucleation catalyzation can occur from:
Respuesta
  • ARF.
  • KDEL.
  • ARP2/3.
  • Formin.
  • Furin.

Pregunta 135

Pregunta
Formins:
Respuesta
  • help catalyze nucleation.
  • capture 2 actin molecules to begin nucleation.
  • dimerize.
  • continue to associate with actin at the plus end.
  • dissociate after nucleation.

Pregunta 136

Pregunta
ARP2/3:
Respuesta
  • is structurally similar to actin.
  • has a different plus end compared to actin.
  • allows actin monomers to bind at plus end.
  • remains bound to (-) end of actin polymer.
  • needs an activating factor to free it from accessory proteins that hold its active site out of orientation.
  • is most efficient at a 70 degree angle to preformed actin filament.
  • is associated with leading edge of migrating cells to allow cellular direction change.

Pregunta 137

Pregunta
Actin can hydrolyze its bound ATP:
Respuesta
  • anytime at the same rate.
  • quicker when in a filament.
  • quicker as a monomer.
  • never.

Pregunta 138

Pregunta
Actin-ADP is:
Respuesta
  • more likely to exist in a filament.
  • more likely to exist as a monomer.
  • more likely to dissociate from the filament.
  • less likely to dissociate from the filament.

Pregunta 139

Pregunta
If the rate of adding subunits to an actin filament is faster than the rate of ATP hydrolysis:
Respuesta
  • Now the filament has an ATP cap.
  • Now the filament has an ADP cap.

Pregunta 140

Pregunta
But, if the rate of subunit addition is low:
Respuesta
  • ADP hydrolysis occurs faster, allowing an ADP cap to form.
  • The world explodes.

Pregunta 141

Pregunta
Treadmilling:
Respuesta
  • makes me tired.
  • involves net addition at the minus end and net loss at the plus end simultaneously.
  • involves net addition at the plus end and net loss at the minus end simultaneously.

Pregunta 142

Pregunta
During treadmilling, the filament is changing length.
Respuesta
  • True
  • False

Pregunta 143

Pregunta
Thymosin:
Respuesta
  • binds to actin subunits, preventing binding to (+) or (-) end.
  • this is because thymosin blocks the area of the protein that hooks on to the filament.
  • thymosin blocks ATP binding site.

Pregunta 144

Pregunta
Profilin:
Respuesta
  • decreases rate of elongation.
  • binds to plus side of actin monomer.
  • favors hydrolysation of ATP to ADP.
  • is thought to bind to some formins to "stage" for action on the polymer.

Pregunta 145

Pregunta
Regulation of thymosin and profilin affect overall actin filament formation.
Respuesta
  • True
  • False

Pregunta 146

Pregunta
Cofilin:
Respuesta
  • binds filaments forcing tight twisting in the structure.
  • helps add monomers to the plus end of the filament.
  • weakens the contacts between subunits.
  • makes actin-ADP dissociation easier.
  • makes actin-ATP association easier.
  • binds preferentially to actin-ADP units.
  • destroys new filaments moreso than old ones.
  • has effects blocked by tropomyosin.
  • increases rate of disassembly.

Pregunta 147

Pregunta
Capping proteins stabilize ends of filaments.
Respuesta
  • True
  • False

Pregunta 148

Pregunta
Capping proteins are made where actin must be stable for long periods of time, like muscle cells.
Respuesta
  • True
  • False

Pregunta 149

Pregunta
Microfilaments are necessary for:
Respuesta
  • cytokinesis.
  • cleavage furrow.

Pregunta 150

Pregunta
Microtubules are the thickest of the cytoskeletal structures at 30nm.
Respuesta
  • True
  • False

Pregunta 151

Pregunta
MTs are hollow and built from:
Respuesta
  • 11 parallel protofilaments.
  • 13 parallel protofilaments.
  • 15 parallel protofilaments.

Pregunta 152

Pregunta
An MTOC:
Respuesta
  • is a microtubule organizing center.
  • is a centrosome in mammalian cells.
  • is on each end of a MT.

Pregunta 153

Pregunta
MTs determine the position of cytoplasmic organelles including vesicles.
Respuesta
  • True
  • False

Pregunta 154

Pregunta
MTs direct movement of chromosomes during cell division.
Respuesta
  • True
  • False

Pregunta 155

Pregunta
Tubulin:
Respuesta
  • is a heterodimer.
  • is composed of 3 globular proteins, alpha, beta, gamma subunits.
  • has its globular proteins held together via noncovalent bonds.
  • has alpha and beta subunits.
  • has two nucleotide binding domains for GTP (alpha, beta).
  • GTP is bound at the intersection between the alpha and beta subunits, and can be hydrolyzed.
  • GTP is bound to the beta subunit, and can be hydrolyzed by the beta subunit itself.
  • Alpha subunit is a GTPase.

Pregunta 156

Pregunta
What kind of contacts occur between tubulin subunits?
Respuesta
  • lateral
  • longitudinal
  • these contacts allow MTs to be stiff

Pregunta 157

Pregunta
MT alpha subunits are exposed at the minus end.
Respuesta
  • True
  • False

Pregunta 158

Pregunta
MT beta subunits exposed at minus end.
Respuesta
  • True
  • False

Pregunta 159

Pregunta
MT elongation involves:
Respuesta
  • tubulin-GTP binding to the plus end.
  • tubulin-GTP hydrolysis to tubulin-GDP while part of the filament.
  • tubulin-GDP causes curvature to form, weakening MT structure.
  • GTP caps can be formed if polymerization is faster than GTP hydrolyzation.

Pregunta 160

Pregunta
Dynamic instability has:
Respuesta
  • shrinking phase called catastrophe.
  • growing phase called rescue.

Pregunta 161

Pregunta
MT are nucleated at centrosomes.
Respuesta
  • True
  • False

Pregunta 162

Pregunta
A centrosome:
Respuesta
  • has a pair of centrioles.
  • is composed of fibrous centrosome matrix.
  • has about 50 gamma tubulins.
  • divides during interphase to aid with mitosis.
  • has many proteins in the matrix, that catalyze addition of tubulins.

Pregunta 163

Pregunta
Gamma tubulin:
Respuesta
  • is more abundant than alpha and beta units.
  • is involved in nucleation.

Pregunta 164

Pregunta
Gamma tubulin ring complex (gamma TuRC):
Respuesta
  • is formed from gamma tubulin and other proteins.
  • allows nucleation to occur.
  • binds the plus end of tubulin subunits to its minus end.
  • caps the minus end of the MTs.

Pregunta 165

Pregunta
Stathmins:
Respuesta
  • bind to tubulin subunits to prevent binding to the polymer.
  • facilitate tubulin binding to the polymer.
  • cap the end of the MT to prevent subunit binding.

Pregunta 166

Pregunta
MAPs (MT associated proteins):
Respuesta
  • prevent binding of subunits to the polymer.
  • bind to the polymer to stabilize.
  • bind to subunits to prevent interaction with the polymer.

Pregunta 167

Pregunta
Kinesin 13:
Respuesta
  • has motor activity.
  • attaches to the end of the MT to create a stabilizing cap.
  • pries apart the end of a MT.
  • does not interact with the end of the MT.

Pregunta 168

Pregunta
XMAP215
Respuesta
  • allows anaphase to occur.
  • can stabilize MT ends.
  • can be phosphorylated to be deactivated.
  • is not a MAP.

Pregunta 169

Pregunta
TIPs:
Respuesta
  • are plus end tracking proteins.
  • are plus end tubulin proteins.
  • can attach and stabilize the growing MT to different locations in the call.
  • accumulate and remain attached at the plus end.

Pregunta 170

Pregunta
Intermediate filaments:
Respuesta
  • are about 10 nm in width.
  • are the thickest filaments.
  • are required for correct cell functioning.
  • can have varied compositions.
  • are constructed only from a particular protein subunit.
  • can be constructed from keratin, vimentin, lamins, etc.

Pregunta 171

Pregunta
IMs can attach to cell junction proteins.
Respuesta
  • True
  • False

Pregunta 172

Pregunta
IMs are:
Respuesta
  • strong.
  • weak.
  • brittle.
  • bendable.
  • easy to break.
  • difficult to break.

Pregunta 173

Pregunta
Why are IMs unique?
Respuesta
  • different monomers.
  • assemble in nonpolar fashion.

Pregunta 174

Pregunta
IM structure:
Respuesta
  • two monomers form coiled-coil dimer.
  • each monomer has globular domain at each N & C terminus.
  • monomers have small, short alpha helical structure.
  • 10 protofilaments made up of pentamers form intermediate filament.
  • 8 protofilaments made up of tetramers form intermediate filament.

Pregunta 175

Pregunta
Strong lateral connections give IFs rope-like character.
Respuesta
  • True
  • False

Pregunta 176

Pregunta
IFs:
Respuesta
  • outer skin layer made of keratin that functions as a barrier.
  • support and anchor structures to maintain shape.
  • line the outside of the lining of the nuclear envelope.
  • provide strength to long axons of neurons.

Pregunta 177

Pregunta
Different cytoskeletal filaments have different motor proteins.
Respuesta
  • True
  • False

Pregunta 178

Pregunta
Myosin moves on:
Respuesta
  • actin, toward (+)
  • actin, toward (-)
  • MT, toward (+)
  • MT, toward (-)

Pregunta 179

Pregunta
Myosin:
Respuesta
  • is a large family of 37+ motor proteins.
  • typically refers to myosin II.
  • are all (-) end-directed.
  • is a two-headed dimer.
  • has alpha helices that form a coiled-coil tail.
  • has two small chains.

Pregunta 180

Pregunta
Coiled coils of myosin:
Respuesta
  • have heptad (7) aa repeat sequence.
  • have hydrophobic side chain interactions on 1st and 4th amino acids.
  • have hydrophobic side chain interactions on 2nd and 4th amino acids.
  • hydrophobic side chains weakly bind to form a superhelix.

Pregunta 181

Pregunta
Myosin thick filaments:
Respuesta
  • are formed by bundles of myosin motor proteins that form a polar contractile unit.
  • have a bare zone in the middle of the filament that has no myosin.
  • has myosin going one way on one side and another way on the opposite side.
  • myosin III is used to make myosin thick filaments.

Pregunta 182

Pregunta
Muscle contraction occurs because:
Respuesta
  • myosin shortens.
  • myosin and actin slide past each other.
  • myosin and actin shorten.
  • myosin filaments slide past each other.

Pregunta 183

Pregunta
Long thin muscle fibers:
Respuesta
  • are actually very large single cells.
  • are several cells lined up on a filament.
  • have majority of cytoplasm made up of myofibrils.
  • have most of cytoplasm filled with mitochondria.
  • have contractile units called sarcomeres.

Pregunta 184

Pregunta
Sarcomeres:
Respuesta
  • are arrays of parallel and overlapping thick (myosin) and thin (actin) filaments.
  • span from Z disc to Z disc.
  • have capZ proteins that cap and stabilize myosin heads.
  • have capZ proteins that cap and stabilize actin heads.
  • span from Z disc to capZ to Z disc to capZ.

Pregunta 185

Pregunta
Tropomodulin:
Respuesta
  • caps actin on (-) end.
  • caps actin on (+) end.
  • caps myosin on (-) end.
  • caps myosin on (+) end.

Pregunta 186

Pregunta
Straitions seen in sarcomeres are:
Respuesta
  • dark bands of actin.
  • dark bands of myosin.
  • light bands of actin.
  • light bands of myosin.

Pregunta 187

Pregunta
Thick filaments during contraction:
Respuesta
  • walk towards Z disc.
  • walk towards bare zone.
  • are driven by ~300 myosin heads that each have.
  • are driven by ~30 myosin heads that each have.

Pregunta 188

Pregunta
Sarcomere shortens __% of length in __ time.
Respuesta
  • 10%, 1/50th second
  • 20%, 1/50th second
  • 10% 1/100th second
  • 20%, 1/100th second

Pregunta 189

Pregunta
Z disc caps (+) and (-) ends of actin.
Respuesta
  • True
  • False

Pregunta 190

Pregunta
M line is another descriptor of the "bare zone."
Respuesta
  • True
  • False

Pregunta 191

Pregunta
M-line contains:
Respuesta
  • myosin heads.
  • myosin coiled-coil tails.
  • actin filaments.
  • actin coiled-coil tails.

Pregunta 192

Pregunta
Nebulin:
Respuesta
  • binds to actin and spans the length of it. Acts like a molecular ruler.
  • binds to myosin and spans the length of it. Acts like molecular ruler.
  • binds to actin and connects end to Z disc. Acts like molecular spring.
  • binds to myosin and connects end to Z disc. Acts like molecular spring.

Pregunta 193

Pregunta
Which accessory protein binds to myosin and acts like a spring that spans from M line to the Z disk?
Respuesta
  • Titin
  • Nebulin

Pregunta 194

Pregunta
Troponin is complex of 3 polypeptides essential for beginning muscle ____________ made up of __________.
Respuesta
  • muscle contraction; Trop I, Trop T, Trop C.
  • muscle contraction; Trop I, Trop T, Trop R.
  • muscle relaxation; Trop I, Trop T, Trop C.
  • muscle relaxation; Trop I, Trop T, Trop R.

Pregunta 195

Pregunta
Tropomysin binds:
Respuesta
  • along the groove of actin helix.
  • along the groove of myosin helix.

Pregunta 196

Pregunta
In absence of Ca2+, Troponin I binds to Troponin T to make I-T complex.
Respuesta
  • True
  • False

Pregunta 197

Pregunta
Troponin IT complex formation:
Respuesta
  • pulls tropomyosin out of groove.
  • allows tropomyosin back into the groove.
  • hydrolyzes tropomyosin.
  • phosphorylates tropomyosin.

Pregunta 198

Pregunta
Which troponin binds to tropomyosin:
Respuesta
  • I
  • T
  • C

Pregunta 199

Pregunta
Muscle contraction steps:
Respuesta
  • SR releases Ca2+ which binds to Troponin C.
  • Tropomyosin moves out of its groove.
  • Myosin head can now bind to actin after ATP binding.
  • Myosin head can now bind to actin after GTP binding.
  • Binding and hydrolysis of ATP/GTP causes conformational change in converter domain.
  • Swinging of lever arm causes head to move along actin.

Pregunta 200

Pregunta
Let's start with contraction just ended:
Respuesta
  • Myosin is attached to actin microfilament without a nucleotide.
  • Head is at 45 degree angle to filament.
  • Head is at 60 degree angle to filament.
  • ATP quickly binds and causes a conformational change in lever arm.
  • Myosin dissociates from actin.
  • As Ca2+ is taken up into SR by calcium P pump, Troponin I & T form IT complex.
  • ATPase myosin activity cleaves ATP to ADP and Pi.
  • Conformational change causes lever arm to swing 90 relative to filament, binds to actin.
  • Inorganic phosphate released, causing lever arm to return to 45 degree angle (the power stroke).
  • Myosin head loses ADP.

Pregunta 201

Pregunta
Rigor mortis:
Respuesta
  • begins a few hours after death and dissapates 48-60 hours after death.
  • is caused by a lack of ATP.
  • involves myosin being "stuck" in position.
  • dissipates after thermal energy causes myosin to break down.
  • ends when enzymes involved in degradation break down myosin heads.
  • is sped up by cold.

Pregunta 202

Pregunta
Kinesin:
Respuesta
  • is a motor protein.
  • mostly move vesicles and organelles toward the (-) end of MTs.
  • commonly refers to Kinesin II.
  • has a heavy chain on N terminus, the motor domain.
  • is involved in superfamily of at least 14 members.

Pregunta 203

Pregunta
Which region of kinesin has conformational changes during ATP binding and hydrolysis?
Respuesta
  • binder domain.
  • linker region.
  • either motor head domain.
  • alpha helical tail.

Pregunta 204

Pregunta
Kinesin C terminus holds cargo.
Respuesta
  • True
  • False

Pregunta 205

Pregunta
Has a similar function and a similar sequence to myosin II.
Respuesta
  • True
  • False

Pregunta 206

Pregunta
Select the steps of mechanochemical kinesin cycle:
Respuesta
  • Heads work in walking motion fueled by ATP.
  • Kinesin is typically bound to ADP, which will bind weakly to MT once contact made.
  • Kinesin-ADP becomes Kinesin-ATP.
  • Kinesin ATP will bind weakly to MT. Conformational change of ATP binding causes lagging strand to zip forward 8nm.
  • ATP hydrolyzed at on new lagging head.
  • New leading strand releases ADP and binds ATP with MT.
  • Lagging strand propelled forward.
  • Cool note. MT bound tightly by kinesin ATP, just like myosin II binds tightly to actin without nucleotide.

Pregunta 207

Pregunta
Dynein:
Respuesta
  • moves vesicles and organelles towards the center of the cell.
  • is involved in separation of chromatids during anaphase.
  • includes cytoplasmic dynein with 2 large head motor domains and 2 light domains.
  • includes complex axonemal dynein with 3 large heads and many light chains.
  • are the slowest motor proteins.

Pregunta 208

Pregunta
Dynein function:
Respuesta
  • large motor head in a ring at C terminal domain.
  • has 6 AAA domains, 4 of which retain ATPase activity with one primary.
  • has tail that carries cargo.
  • has long coiled-coil stalk that binds MT.
  • ATP hydrolysis causes attachment of stalk to MT.
  • release of ADP and Pi leads to the large power stroke conformational change.
  • 8nm steps toward (-) of MT.

Pregunta 209

Pregunta
Kinesin directs vesicles and organelles to cell exterior.
Respuesta
  • True
  • False

Pregunta 210

Pregunta
Cdc42 yields large number of filopodia made of MTs.
Respuesta
  • True
  • False

Pregunta 211

Pregunta
Rac, Rho, cdc42 are small G proteins that alter actin skeleton.
Respuesta
  • True
  • False

Pregunta 212

Pregunta
Taxol kills rapidly dividing cells by stabilizing MTs.
Respuesta
  • True
  • False
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