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BIO 2600 > Chapter 15 > Flashcards

Chapter 15 Flashcards

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1
Q

ways that eukaryotic cells segregate chemical processes

A

membrane-enclosed organelles
phase separation of protein complexes (biomolecular condensates)
membrane contact sites, non vesicular communication

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2
Q

nucleus characteristics

A

outer and inner membrane
outer membrane continuous with ER
nuclear inter membrane space continuous with ER lumen
communicates with cytosol through nuclear pores

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3
Q

rough ER characteristics

A

site of new membrane synthesis
ribosomes on the cytosolic side synthesize proteins that are sorted into the ER membrane or lumen

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4
Q

smooth ER characteristics

A

steroid hormone synthesis; lipid synthesis
Ca+2 stores-uptake and release in response to extracellular signals (neuron signaling)

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5
Q

free ribosomes function

A

synthesis of cytosolic proteins

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6
Q

Golgi apparatus function

A

modifies proteins and lipids from the ER on their way to other cell compartments or EC space (sorting)

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7
Q

lysosome characteristics

A

breaks down damaged organelles and endocytosed macromolecules
signaling
acidic

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8
Q

Peroxisome function

A

breaks down lipids
detoxification

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9
Q

membrane invagination mechanism

A

nuclear membrane and ER believed to have evolved from invagination of the PM

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10
Q

endosymbiosis

A

mitochondria and chloroplasts may have evolved from uptake of aerobic bacteria

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11
Q

three mechanisms of protein import into organelles

A

transport through nuclear pores
transport across membranes by translocators
vesicular transport

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12
Q

sorting signal

A

N-terminal sorting sequence directs protein to organelle where it is required
no sequence = proteins stay in cytosol
15-60aa long
often cleaved after sorting

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13
Q

protein sorting to nucleus and mitochondria

A

proteins synthesized in cytosol delivered directly to nucleus and mitochondria

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14
Q

protein sorting within endomembrane system

A

ER synthesizes proteins/lipids and receives proteins from the cytosol
some retained in ER, but most packaged in vesicles for transport to Golgi, then to lysosomes, endosomes, inner nuclear membrane, and PM

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15
Q

peroxisome protein sorting

A

use direct from cytosol and indirect (vesicular via ER)

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16
Q

inner nuclear membrane proteins

A

binding sites for chromosomes and anchorage for nuclear lamina

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17
Q

nuclear pores function

A

allow mRNA and ribosomal subunits to move out and nuclear proteins to move in
allow protein transport in folded form

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18
Q

nuclear pores structure

A

~30 proteins have short disordered repeats that extend to the pore center and create a web
prevents large molecules but allows small hydrophilic molecules through

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19
Q

nuclear localization signal

A

polybasic motif (several positively charged Lys and Arg) that directs proteins from cytosol to nucleus

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20
Q

nuclear import receptor

A

cytosolic protein directs proteins through the nuclear pore

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21
Q

energy for nuclear transport supplied by:

A

GTP hydrolysis

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22
Q

GTP hydrolysis in nuclear transport

A

-nuclear protein binds to receptor and complex enters nucleus
-Ran-GTP displaces imported protein
- receptor/Ran-GTP complex leaves nucleus
-GTP is hydrolyzed and Ran GDP dissociates from the receptor (Ran-GDP has less affinity for receptor)
-receptor is free to pick up another protein for translocation

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23
Q

function of Ran-GAP accessory protein

A

GTPase activating protein
only found in cytosol
facilitates GTP->GDP hydrolysis
promotes binding of import receptor to cargo

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24
Q

Ran-GEF function

A

Guanine exchange factor
present in the nucleus
promotes exchange of GDP with GTP and cargo dissociation from receptor

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25
what concentrations must be maintained for nuclear protein transport
high concentration of Ran-GTP in nucleus to displace imported protein high concentration of Ran-GDP in cytosol, produced by GTP hydrolysis maintained by accessory proteins
26
protein transport into mitochondria/chloroplasts
signal sequence binds to receptor in outer membrane receptor, protein, and translocator diffuse within outer membrane until contact with second translocator in inner membrane two translocators transport protein simultaneously across both membranes (UNFOLD in the process)
27
Chaperons function in mitochondrial protein transport
help pull protein through the membrane and refold it
28
signal peptidase function
cleaves signal sequence
29
two types of proteins entering ER
water-soluble proteins: pass through membrane into lumen, eventually reach lumen of specific organelle or EC space transmembrane proteins: embedded into ER membrane, eventually transported to PM or membrane of another organelle
30
cytosolic ribosomes vs ER bound ribosomes
cytosolic ribosomes stay free in the cytosol ER bound ribosomes attached to cytosolic side of ER all ribosomes return to common pool and interchange between free/attached depending on the code of mRNA it is translating
31
polyribosome
many ribosomes bind to each mRNA at the same time
32
N-terminal ER signal sequence effect
read first by ribosome, directs ribosome to bind to cytosolic surface of ER
33
signal recognition particle (SRP)
binds to ER signal sequence and ribosome slows down synthesis until complex is attached to ER surface
34
SRP receptor
embedded in ER membrane binds to SRP/ribosome/mRNA/polypetide complex displaces SRP polypeptide passes through protein translocator into ER lumen, speeding up synthesis
35
translocation of water soluble protein into ER lumen
opens upon binding with signal sequence translocates polypeptide as it is being synthesized by ribosome signal peptidase cleaves sequence and translocated polypeptide released into ER lumen (cleaved signal sequence remains in ER membrane)
36
single-pass transmembrane protein synthesis in ER membrane
start transfer sequence initiates translocation through translocator protein passes through translocator until stop transfer is reached start transfer cleaved off and protein is released from translocator leaving it anchored within the membrane
37
stop transfer sequence
stretch of hydrophobic aa within the protein that keeps that section of protein within the ER membrane
38
multi-pass transmembrane protein insertion into ER membrane
combination of start and stop transfer sequences initiates and ends translocation of protein neither sequence cleaved off
39
peroxisomal protein transfer characteristics
most enter via selective transport from cytosol short (3aa) import signal recognized by receptor protein for delivery contain translocator proteins do not unfold to enter SOME proteins arrive via vesicular transport
40
lipids transported to mitochondria at ___________ by ______________
membrane contact sites (MCS); lipid transfer proteins (LTPs) (also can be transported by vesicles)
41
LTP structure
form tunnels with hydrophobic core
42
ERMES
ER mitochondria encounter structure a multi protein complex that allows lipid transfer and tethering of ER and mitochondria
43
where do clathrin-coated vesicles bud from
PM in endocytosis and from Golgi
44
what are COP-coated vesicles involved in
transporting molecules from ER to the Golgi and from Golgi back to ER
45
COP-II coated vesicles bud from where
bud from ER and go to Golgi
46
COP-I vesicles bud from where
from Golgi to ER
47
protein coat function
shape membrane into curved budding vesicle capture cargo for transport shed off when budding complete
48
Clathrin coated vesicle transport process
cargo receptors in membrane bind to cargo and adaptin on the other side adaptin binds cargo receptors to clathrin dynamin hydrolyzes GTP and pinches off vesicle from membrane
49
clathrin mediated endocytosis
important for recycling vesicles needed for neurotransmitter release
50
effects of dynamin mutations
paralysis in animal models
51
Rab (GTPase) function in vesicle docking
initial recognition; located on vesicle, identifies the vesicle and attaches to tethering protein on target membrane
52
docking process of vesicles
after Rab binds to tethering protein, the complemetary SNARE proteins wrap around each other to fuse the membranes together and remove water molecules interacting with vesicle
53
v-SNARE versus t-SNARE
v on vesicle t on target membrane
54
secretory pathway order
ER -> Golgi -> (PM for secretion) OR (lysosome for degradation)
55
Disulfide bonds formation
form between S atoms of adjacent cysteine side chains takes place by oxidation in ER lumen ONLY important for secreted proteins to maintain function and conformation
56
N-linked glycosylation
short oligosaccharides attached to proteins (synthesize glycoproteins) starts in ER completed in GOLGI protects proteins from degradation, guides protein to correct transport vesicle, form glycocalyx
57
process of N-linked glycosylation
large oligosaccharide linked to dolichol (lipid) is transferred to growing polypeptide chain when Asn is produced attached to amino (NH2) group of asparagine further processing and differentiation happens in the Golgi
58
Chaperone proteins function in ER
help correctly fold newly synthesized proteins in ER
59
how are proteins that function in the ER kept there
ER retention signal
60
what happens to misfolded proteins, disease that is a result of this
transported to cytosol for degradation by proteasomes cystic fibrosis: misfolded Cl- channels that are still functional are degraded due to extreme quality control
61
Unfolded protein response (UPR)
happens due to buildup of misfolded proteins in the ER can cause increased folding capacity of ER, transcription/translation reduction, and possibly triggers cell death
62
Golgi function
oligosaccharide modification sort to lysosome or cell surface cis Golgi sends proteins with ER retention signal back to ER
63
movement within and to golgi
proteins travel from the ER to Golgi in COP-II coated vesicles movement within Golgi by vesicles or maturation move from cis to trans face
64
constitutive secretion
continual secretion from cells operates in all cells regardless of signals
65
regulated secretion
operates in specialized secretory cells produce large quantities of cargo, stored in secretory vesicles (concentrated by aggregation) extracellular signal stimulates secretion
66
endocytic pathways
phagocytosis, pinocytosis, receptor mediated endocytosis
67
phagocytosis
ingestion of large particles (microorganisms, debris) via phagosomes clathrin required, selective process purpose: nutrition and defense phagosomes fuse with lysosomes
68
pinocytosis
used to "sample" EC environment fluid uptake containing solutes endocytic vesicles fuse with endosomes which fuse with lysosomes nonselective MAINTAIN membrane volume, balance exocytosis
69
receptor mediated endocytosis
highly specific endocytose specific molecules by forming clathrin coated endocytic vesicle increases cargo concentration hijacked by viruses
70
import of cholesterol process
cholesterol packaged in LDL particles, which are secreted to the blood, binds receptors on cells, ingested by clathrin mediated vesicles, enters endosome (acidic), receptor and LDL dissociate, LDL to lysosome, broken down and frees cholesterol to cytosol
71
what would be caused by mutations in LDL receptor
unable to uptake LDL/cholesterol from blood, high blood cholesterol, treated with statin
72
endosomes characteristics and function
early/late endosomes sort incoming molecules acidic due to H+ pumps breaks apart receptor/ligand complexes sends to same location (recycles), lysosome (degradation), or different location (transcytosis)
73
digestion in the lysosome
contain acid hydrolases (hydrolytic enzymes) that function at low pH H+ pump maintains acidity
74
lysosomal membrane proteins
highly glycosylated for protection receives proteins from endomembrane system (ER - Golgi) tagged with mannose-6-phosphate
75
autophagy
degradation of unnecessary or dysfunctional cellular components (selective) autophagosomes envelop target component
76
lipophagy
specialized autophagy of lipid droplets regulates lipid content TAG -> supplies free fatty acids to sustain energy/ ATP levels triggered by nutrient depletion/starvation
77
function of IRE1 in UPR
transmembrane with kinase and nuclease domains on cytosolic side activated > adjacent kinases phosphorylate each other > enables RNase domains > RNase cleaves specific mRNA at 2 positions to excise introns spliced mRNA exons joined (RNA ligase) > translated into transcription regulatory protein that enters nucleus and activates transcription of genes to expand ER and increase folding capacity
78
PERK function in UPR
transmembrane kinase activated by misfolded protein accumulation > phosphorylates itself > phosphorylates translation initiation factor (inactivating it) > inhibits overall protein synthesis, increases transcription of genes for UPR proteins
79
ATF6 function in UPR
transmembrane protein with transcription regulator (TRP) to be delivered to nucleus > vesicle forms and sends protein to Golgi > proteases cleave cytosolic domains (TRP) which are then free in cytosol > enter nucleus and activates transcription of genes encoding UPR proteins

BIO 2600 (15 decks)

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