Ch. 15 Smartwork (Exam 3)

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52 Terms

1
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The outer membrane of the nucleus is continuous with the membrane of which other organelle?

endoplasmic reticulum

2
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Which organelle is the major site of new membrane synthesis in a cell?

endoplasmic reticulum

3
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Which organelle receives proteins and lipids from the endoplasmic reticulum, modifies them, and then dispatches them to other destinations in the cell?

golgi apparatus

4
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Soluble proteins and pieces of membrane enter the Golgi network via

transport vesicles derived from the ER

5
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Proteins exit from the Golgi network in transport vesicles destined for either

the cell surface or another organelle of the endomembrane system

6
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How do the interiors of the ER, Golgi apparatus, endoscopes, and lysosomes communicate with each other?

by small vesicles that bud off of one organelle and fuse with another

7
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Which membrane-enclosed organelles most likely evolved in a similar manner?

the nucleus and the ER

8
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The nuclear membranes and the membranes of the ER most likely originated by

invagination of the plasma membrane

9
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The outer nuclear membranes is continuous with the

rough ER

10
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In muscle cells, which organelle sequesters Ca2+ from the cytosol?

smooth ER

11
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In muscle cells, the specialized smooth ER is called the

sarcoplasmic reticulum

12
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In a typical human secretory cell, what membrane has the largest surface area?

rough ER

13
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The rough ER is folded up to form

an extensive maze of interconnected spaces

  • mostly composes about ½ of the total membrane present in the cell

14
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IkB blocks the nuclear localization signal of

NFkB until it is ubiquitinated and degraded after stimulation

15
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Once IkB is degraded, the nuclear localization signal on NFkB can be

recognized by the nuclear import receptor

16
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Blocking IkB degradation would inhibit

NFkB transport

17
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Adding excess nuclear location signal peptide would also block import of NFkB because

the set amount of nuclear import receptor would be binding the large excess of peptides instead of the actual proteins to be imported

18
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Once the nuclear import receptor transports charge into the nucleus,

ran-GTP helps export the nuclear receptor out of the cytosol

19
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Ran is converted to Ran-GDP by the

Ran-GAP protein in the cytosol and then moves back to the nucleus

20
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Proteins that lack a sorting signal remain as permanent residents of which part of a eukaryotic cell?

cytosol

21
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What would happen to a protein that is engineered to contain both a nuclear localization signal and a nuclear export signal?

it would shuttle in and out of the nucleus

22
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Proteins that escort mature mRNAs from the nucleus to the cytosol need

an export signal to leave the nucleus and a localization signal to re-enter

23
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Which proteins bind to nuclear localization signals on newly synthesized proteins?

nuclear import receptors

24
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The nuclear localization signal on proteins destined for the nucleus is recognized by cytosol in proteins called

nuclear import receptors

25
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Nuclear import receptors help direct newly synthesized proteins to a nuclear pore by

interacting with the tentacle-like fibrils that extend from the rim of the pore into the cytosol

26
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What actions occur commonly at a nuclear pore complex?

  • nuclear import receptors are exported to the cytosol

  • mRNA molecules are exported to the cytosol

  • nuclear import receptors enter from the cytosol

  • proteins with a nuclear localization signal enter at the same time that proteins with a nuclear export signal exit

27
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Proteins destined for the Golgi apparatus, endosomes, lysosomes, and even the cell surface must pass through which organelle?

endoplasmic reticulum

28
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Which is true of ribosomes?

a common pool of ribosomes is used to synthesize both cytosol if proteins and proteins destined for the ER

29
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When a ribosome is making a protein that has an ER signal sequence,

that signal sequence directs the ribosome to the ER membrane

30
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As a polypeptide is being translocated across the membrane of the ER, a stop-transfer sequence can halt the process. What eventually becomes of this stop-transfer sequence?

it forms an alpha-helical membrane spanning segment of the protein

31
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The ER signal sequence on a growing polypeptide chain is recognized by a signal-recognition particle (SRP) in the cytosol. What does this interaction accomplish?

it guided the ribosome and its polypeptide to the ER

32
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The SRP binds to both the

exposed ER signal sequence and the ribosome

  • the SRP-ribosome complex then binds to an SRP receptor in the ER membrane

33
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Free ribosomes are structurally identical to those that

are bound to the ER

34
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When a ribosome happens to be making a protein with an ER signal sequence,

the signal sequence directs the ribosome to the ER membrane

35
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Membrane-bound ribosomes and free ribosomes are structurally and functionally

identical; they differ only in the proteins they are making at a particular time

36
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Which organelle cannot receive proteins directly from the cytosol?

Golgi apparatus

37
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Proteins are delivered to the Golgi apparatus from the

ER or from other components of the endomembrane system

38
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What is the source of energy for protein translocation into the ER?

synthesis of the protein

39
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Proteins with an ER signal sequence are translocated as they are being made;

the elongation of the polypeptide provides the thrust needed to push the growing chain through the ER membrane

40
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Nuclear import is driven by the hydrolysis of GTP, which is triggered by an accessory protein called Ran-GAP (GTPase-activating protein). What is true of this process?

nuclear receptors carry Ran-GTP from the nucleus to the cytosol

41
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What enables proteins destined for nuclear import to pass through the nuclear pore?

they are recognized by receptors that interact with repeated amino acid sequences in proteins lining the nuclear pore

42
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Since glycosylation is on the extracellular side of the plasma membrane, the C term is

in the extracellular space and the N terminus is in the cytosol

43
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Glycosylation occurs inside the

lumen of the ER and Golgi apparatus

44
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Where in the cell are some proteins initially decorated with an oligosaccharide tree on asparagine residues?

ER

45
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Glycosylation begins with the addition of a

preformed oligosaccharide in the ER

46
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If proteins cannot leave the ER, they will never make it to

the Golgi apparatus

47
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What best describes a pathway that a protein might follow from synthesis to secretion?

Cytosol → ER → transport vesicle → Golgi apparatus → transport vesicle → plasma membrane

48
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How are newly made lipids supplied to the plasma membrane?

via the constitutive pathway of exocytosis

49
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How are proteins destined to function in the ER retained there?

they contain a C-terminal ER retention signal

50
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Increasing Ca2+ concentration directly or through opening pores will trigger

vesicle fusion with the plasma membrane increasing muscle contraction

51
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Cleaving SNAREs and blocking GTP binding inactivate

SNARE and Rab respectively, leading to decreased muscle contraction

52
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What accurately describes a step in GTP-driven nuclear transport?

binding of Ran-GTP to the receptor releases the cargo protein