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BMSC 220 > Topic 8 > Flashcards

Topic 8 Flashcards

1
Q

ribosomes are located in…

A

the cytosol; either free or on membrane bound organelles

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2
Q

synthesis of ALL proteins start on…

A

free ribosomes; then can continue membrane bound

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3
Q

two major branches of protein sorting

A

cytosolic and secretory

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4
Q

targets of cytosolic pathways

A

nucleus, mitochondria, chloroplasts, peroxisome

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5
Q

in cytosolic pathway, protein synthesis starts in ________ and finishes in _________.

A

cytosol, cytosol

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6
Q

targets of secretory pathway

A

nuclear membrane proteins, ER proteins, golgi proteins, endoscopes, lysosomes, secretory vesicles, plasma membrane

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7
Q

secretory pathway protein synthesis starts in ________ and finishes in ________.

A

cytosol, ER

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8
Q

cytosolic pathways moved to final destination through recognition of…

A

specific targeting amino acid sequences (signal sequences) within the protein

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9
Q

most cellular compartment have their own….

A

chaperones

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10
Q

What replaces cytosolic chaperones?

A

mitochondrial chaperones

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11
Q

endoplasmic reticulum with ribosomes

A

rough ER

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12
Q

rough ER

A

involved in protein metabolism

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13
Q

smooth ER

A

involved in lipid metabolism and not associated with ribosomes

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14
Q

The ________ is the entry point for most proteins into the secretory pathway.

A

rough ER

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15
Q

co-translational transport

A

when majority of proteins destined for secretory pathway are translocated into ER during synthesis on membrane-bound ribosomes

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16
Q

how does co-translational transport occur?

A

signal hypothesis

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17
Q

C terminus

A

carboxyl terminus; end of peptide

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18
Q

N terminus

A

amino terminus; start of peptide

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19
Q

signal recognition particles, SRPs

A

recognize and bind to signal sequences in the growing protein while it’s still being translated

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20
Q

signal sequences

A

specific amino acid sequences

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21
Q

SRPs are composed of..

A

small, cytoplasmic non-coding RNA and proteins

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22
Q

SRP receptors

A

proteins on the membrane of the ER that bind the SRP

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23
Q

translocon

A

a membrane channel through which polypeptide chains with a signal sequence are transported into the ER

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24
Q

Why is the term “secretory pathway” misleading?

A

It’s not just for secretion of proteins, but carries out sorting of both free and membrane-bound proteins to some intracellular destinations

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25
Q

Players in “Signal Hypothesis”

A
  • signal sequence
  • SRP
  • signal recognition particle receptor
  • translocon
  • signal peptidase enzyme (cleave off signal sequence)
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26
Q

When ribosome sits over translocon channel…

A

protein is synthesized into the channel

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27
Q

After proteins are translocated to ER as unfolded polypeptide chains,….

A

they fold into their 3D conformations

28
Q

passage into ER lumen and ER membranes involve….

A

chaperones (BiP is one in the ER)

29
Q

Intergral membrane proteins must be inserted in the correct orientation in the ER because….

A

they cannot be flipped within the membrane

30
Q

transmembrane sequence

A

stops the polypeptide from entering the lumen of ER and changes conformation of translocon channel so that it opens and releases polypeptide chain to ER membrane

31
Q

Describe Smooth ER and membrane assembly

A

due to hydrophobicity… membrane lipids are synthesized with already existing cellular membranes of the smooth ER

32
Q

flippases

A

enzymes that facilitate translocation of newly synthesized phospholipids to opposite side of bilayer

33
Q

cis face of Golgi

A

closest to ER where proteins enter

34
Q

trans face of the Golgi

A

from ER where proteins exit

35
Q

Sorting off proteins starts in the Golgi… why?

A

ER proteins (BiP) first go to Golgi before they are sent back to the ER

36
Q

mannose-6-phosphate

A

specialized form of oligosaccharide †ha† target proteins for lysosomes

37
Q

_______ of vesicular transport is key to maintaining the functional organization of the cell

A

selectivity

38
Q

2 steps to ensure correct proteins get to their correct final destination

A
  • get correct protein into correct vesicle

- get vesicle to correct final destination

39
Q

Most transport vesicles that carry secretory proteins from the ER to the Golgi and from the Golgi to other targets are coated with cytosolic coat proteins and are called..

A

coated vesicles

40
Q

coated vesicles

A

play a key role in ensuring the vesicles reach their correct targets within the cell following exit from Golgi

41
Q

different kinds of protein coats

A

cathrin, COPI, COPII

42
Q

lysosomes

A

membrane-enclosed organelles that contain enzymes capable of breaking down all types of polymers at acidic pH

43
Q

cathrin-coated vesicle

A

sort through lysosomal proteins

44
Q

most lysosomal enzymes are…

A

acid hydrolases

45
Q

acid hydrolases

A

active at acidic pH that is maintain within lysosomes, but not at neutral pH in rest of cytoplasm

46
Q

proton pumps

A

maintain acidity of lysosome

47
Q

snare hypothesis of vesicle fusion

A

proposal for mechanism of fusion for transport and secretion

48
Q

two stages of snare hypothesis

A
  • transport vesicle must recognize the correct target

- vesicle and target must fuse for purpose of delivering the cargo

49
Q

tethering factors

A

stimulate formation of SNARE complexes between vesicles and target membrane, beginning process of membrane fusion.

50
Q

SNARE-SNARE paring

A

provides energy to drive membrane fusion

51
Q

Rab protein

A

recognize and bind tethering factors on target; forming initial interactions between vesicle and target membrane

52
Q

Nuclear pore complex consists of …

A

a structure with eight-fold symmetry organized around a large central channel

53
Q

nuclear pore complex is composed of ……. different nucleoporins

A

30-50

54
Q

Depending on their size, small polar molecules, ions, and macromolecules can travel through the nuclear pore complex by…

A

passive and energy dependent

55
Q

nuclear localization signals

A

specific amino acid sequences that are recognized by transport receptors and direct the transport of proteins from the cytoplasm through the nuclear pore complex into the nucleus.

56
Q

nuclear transport receptors

A

proteins that recognize nuclear localization signals and mediate transport across the nuclear envelope

57
Q

karyopherins

A

family of nuclear transport receptors

58
Q

importins

A

karypherins that direct nuclear import

59
Q

Ran

A

a GTP-binding protein that regulates movement of importing/cargo complex into nucleus

60
Q

What drives importing movement across th pore?

A

unequal distribution of Ran/GTP

61
Q

nuclear export signals (NES)

A

specific amino acid sequences that target proteins for export from nucleus

62
Q

exportins

A

member of karyopherin family that interact with NES; similar mechnanism as importing

63
Q

RNA transport across nuclear envelope as..

A

ribonucleoprotein complexes (RNPs)

64
Q

rRNAs transport across nuclear envelope as..

A

ribosomal subunits

65
Q

mRNAs transport across nuclear envelope as..

A

in association with two proteins known as mRNA exporter complex

66
Q

tRNAs transport across nuclear envelope as..

A

associated with exporting-t

67
Q

snRNAs transport across nuclear envelope as..

A

assembled into snRNPs and then back into nucleus as splice some complex

BMSC 220 (12 decks)

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