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Cell Bio > Exam 2 - mod 5 > Flashcards

Exam 2 - mod 5 Flashcards

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1
Q

cellular compartments

A

membrane enclosed organelles take up .5 volume of a eukaryotic cell and expand the total surface area 20-30 fold

increases area of cell 20-30 fold

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2
Q

topographically, the interior of the endomem system is equavalent to the

A

extracellular environment

-want proteins doing bizz of golgi to be in golgi

the inside of the endomem system becomes the outside

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3
Q

mfucntions of membrane enclosed compartments of a eukaryotic cell

A

cytosol - contains metabolic pathways (in protein synthesis and the cytoskeleton)

nucleus - contains genomes

ER - synthesize most lipids proteins for distribution to organelles and plasma mem

golgi - godication, sorting, packagins of porteins and lipids

lysosomes - intracellular degradation -hydrolyic enxymes

endosomes - sort endocytosed material

mitochondria - atp synthesis by oxidative phosphorylation

chloroplasts - atp synthesis and carbon fixation by photo synthesis

peroxisomes - oxidation of toxic molecules

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4
Q

mitochondria relative volume and number in mem enclosed organelles

A

lots of mitochondria

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5
Q

the golgi

A

cis golgi -recieves proteins and lipids from ER

trans golgi - where proteins leave
transport vesicles around the outside, deals w packaging and sorting
further destination

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6
Q

protein sorting

A

requires signal sequences and specific receptor proteins

protein sequences some made in cytosol some in ER

transported into organalles by 3 mech
1 transport through nuclear pores

2 transport across membranes

3 transport by vesicles

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7
Q

2 protein synthesis process

A

free ribosomes
-nuclear proteins
-chloroplast and mitochondrial proteins
-cytosolic proteins
no ER signal sequence - remains free in cytosol

ROUGH ER - mem bound ribosome cycle
-most integral mem proteins
secreted proteins
lipids
produce proteins for secretion or mem insertion - encoded with an ER signal sequence

Same riosomes can attach to er or stack up in line

polysomes can make actin or nuclear proteins

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8
Q

cells endomem system

A

nuclear membrane is part of system
aqueous pores conenct the nucleoplasm and cytoplasm

compartmentalize parts of protien synthesis

proteins in nucleus differ from thos in cytosol
`

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9
Q

distinct completments of proteins are present in nucleus and cytoplasm

A

nuclear envelop
pores
lamina
condensed chromatin

transmission electron micrograph of nuclear mem

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10
Q

cytoskeletal network of

A

lamins provides mechanical support to the nuclear face of the mem and binding sites for chromatin

proteins enter/exit by nuclear pores on nuclear envelope

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11
Q

nuclear pores

A

complex architecture with central channel of approx 9nm

density acts as barrier for nuclear diffusion

also attached to the lamina to keep in place

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12
Q

nuclear mem

A

acts a barrier to latereral diffusion of membrane proteins from nuclear to cytoplasmic faces of ER mem

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13
Q

protein diffusion

A

proteins less than 40000 molecular weight diffuse freely through pores on own

larger molecules need carrier proteins and energy from GTP hydrolysis to pass through

pores can expand to diameter of 40 nm.

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14
Q

importins

A

nuclear transport receptors are recycled

proteins have nls for import and nes for export

sequence recog by recepotrs which brings material into nucleus

importins –> nuclear import receptors

exportants –> export proteins

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15
Q

import of proteins are regulated

A

by RAN - small GTP molecular binding protein

protein will bind to import - goes to port in high RAN gtp

release the protein

has helper proteins like RAN -GEF

GEF load gtp into

RAN in nucleus - dense high levels

gap hydrolyzeds gdp to gtp
hydrolyzes GTP once past pores and cytosol

regulated RAN GTPAase binds to importin

using a RAN gradient

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16
Q

nuclear localization signals NLS

A

have basic amino acids in a linear sequence
binds to importins

single importin transports multiple proteins

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17
Q

Summary of nuclear proteins sorting

A

proteins enter nucleus through pores
smaller than 40000 daltson diffuse freely

pores expand to allow passage of larger protein s

nuclear transport proteins importins regulate transport with NLS using energy from GTP exchange

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18
Q

proteins imported to mitochondria chloroplasts and nuclei

A

mit genomes encode small amounts of proteins - subunits of respiratory chain complexes - other subunits encoded by nuclear genes and mush be imported in mitochondria

TOM and TIM complexts tranpsort unfolded proteins across mem

nuclear encoded proteins synthesized w signal sequence + transproted to organelles in complexes w chaperone proteins (importins) GTP and GDP graident controls import

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19
Q

ER

A

more interconencted
where mem and secreted proteins occur

er makes contact w itself and other organelles like mitochondria

likely to deliver lipids

ER contact sites –> ER mitochondrial junctions between ER mem and mitochondrial outter mem - transfering lipids

has other contact sites too

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20
Q

integral mem protein synthesis

A

proteins destined for endomem system are cotranslationally imported into the ER

signal hypothesis - signal sequence

secreted and integral mem proteins
15-35 aa
6-15 non polar aa
co translatioonal

signal recog particle (SRP) binds to protein and brings to channels
7SRNA signal seq is cleavved and cut off

chaperone
glycocylation

every secreted protien ahs sugar on it

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21
Q

process of integral membrane protein synthesis

A

signal reco particle binds signal seq and translation slows or stops

complex docs with SRP receptor in ER

ribosome engaged with translocon - translation resumes

bringing ribosome to translocator
SRP is displaced for reuse

signal sequence cleaved and unfoldded protein passes through the translocon pore

as portein emerges chaperones bind to

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22
Q

structure of signal peptidase

A

h spc - a and spc -c

has bidning pocket : select for shape
membrane thinning : select for length
cleavage: ser-his-asp triad

not cut going into nuclease but can cut in mitochondrai

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23
Q

insertion of transmembrane protein

A

cytosol on one side
ER lumen on other

trans mem proteins
as signal translated

has ER signal equence
goes through translocator

man proteins have multiple pass domaisn

future transmem domains act as start transfer and stop transfer signals for mem proteins

inserted cotranslationally

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24
Q

glycosylation

A

almost all integral and secreted proteins are sugar coated
start in RER
role of glycosyltransferases
donor nucleotide sugars
diff glucosyltransferases in diff membrane compartments

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25
synthesis of core liogosaccharaides in ER
26
glycosylation begins co translationally
always same 2 glucoses ancestral match core is linked to asperagine dolichol phosphate and isoprene units core - acetylglucosamine 1 phsophate mannose glucose trimming of 2 glucose
27
role of chaperone in proper folding
misfolded proteins activate ER sensor proteins which prompts activation of chaperone genes chaperones bind to protiens to proper fold chaperone degrade after and er sensor returns to inactive
28
calnexin chaperone proteins folding cycle in the ER lumen
29
ER site of lipid biosynthesis
enzymes whose active sites face ER lumen however, topologic problem so use flippases --keep ps low on expolasmic leaflet PE high in cytoplasmic leaflet facilitates vesicle budding from ER and golgi cholesterol synthesized there but not maintained at low levels enzymes in ER
30
lipid movements within and between membranes
ER and golgi exchange vesicles and flipping lipids in and out LTP untethered lipid transfer protein moves lipids between bilayers lipid transfer at a mem contact site autoinhibited OSBP
31
ER golgi contact sites
add cholestrol and change orientation of lipids
32
movement of lipids across mem bilayers
flippase in ER P4 type atpase
33
there is a gradient of lipids
in the mem along the secretory pathway
34
effects of lipids on bilayer thickness
sphinglipids sterols and glycerophospholipds sphingomyelin make thicker
35
proteins enter the endomem system
N terminal signal sequences in nascent polypeptides are recog by signal recognition particles and transfered to SRP receptor or ER mem unfolded proteins are transfered through translocon hydrophobic start and stop transfer sequences gives rise to transmem segments of mem proteins
36
how are proteins imported into mitochondrai and chloroplast
cleavable signal sequences at N termini bind receptor in otuer mem, after which the unfolded proteins cross both mems through channels formed by TOM and TIM protein s
36
proteins are cotranslationally imported into endomem syst
N terminal signal sequences in nascentpolypeptides are recog by signal recog particles and transfered to SRP receptor on ER mem unfolded proteins transfered through translocons hydrophobic
37
trafficing through GERL system occurs mainly in vesicles
t
38
temp sensitive yeast mutants have facilitated identification of the protiens invovled in transprot
proteins in secretory pathway proteins secreted protein accumulates in ER accumulates in golgi
39
moving through golgi
most believe in vesicular transport cesternal progression -flowing from one to next lipi partionaing mech fuse and mesh and blocking off
40
golgi enzymes
modify sugar structure orignated in the ER enzymes that add modify and remove sugards are topographically restricted to portions of the ER stack every protein has distinct sugar coating
41
studying enzymes with histochemistry
EM sections are incubated w substrates for diff golgi enzymes ensymes generate insoluble products containing heavy metals by purifying enzymes and altering cis, medial, trans
42
secretory membrane system
make vesicle buds proteins self assemble and diff scaffoldign in diff compartments need to reach microtubuals
43
proteins are transferred through endomem system vesicles
most not all have proteins coats cargo si concentrated in vesicles diff coat protiens are used in diff parts of the golgi
44
coating along secretory patways
copii from er to golgi gop 1 retrograde transport budding off golgi moves to mem using cytoensoal clatherin - secretory genes same protein in endocytosis membranes cant bd and transport itself coating mechanically grabs bud uncoated vesicles - cyotplasm so dence vesicle cant attach and need to be translocated in order to fuse cant have coat cage to mechanically rip vesiccles off mem
45
three homologus vesicle coats
copii copi and clatherin coats cages vertext structures can recog certian cargo clatherin doesnt work alone - has adaptins that help select cargos and bring in insulin proteins regluate them
46
role of small gtp binding protiens
re to golgi Copii coat assocaited sar gtp binding protien sar gtp is small gtp bindign protien helps to assemble cop ii binds to er mem recruits other coat subunits to copii hydrolysis of gtp to gdp intiaties disassembly must disassemble before fusing with target mem to sar gdp releases other copII subunits er to golgi traffic cop ii coat assembly on the er mem
47
assemly of protein cop I
in gtp bound state arf1 GTP bindign protein must be hydrolyzed before coat (8proteins) disassembled golgi to er KDL sequence - KDEL receptor that binds to proteins that have 4 recepotrs in it recoated w copI to bring back to ER KDEL invovled in exocytosis
48
clathrin coated vesicle formation requires
cargo receptors adaptins coat proteins dynamin works w adaptor prteins to recog and go diff compart moving vesicles from golgi to other compartments gtpase dynamin provides energy to release vesicles
49
clathrin in depth
triskilions 3 heavy and 3 light chains have globula ddomains on ends that intersect w protein domains form closed cages adaptor proteins used for post golgi transport and for endocytosis RAb gtpase helps
50
dynamin gtpase in relation to glathrin
hydolysis of gtp dynamin pinches off vesicle mutants gtp shibere paralized fly mutant lots of pits but no endocytosis in nervous system pinch clatherin coated vesicles away from origninal mem contor and contrsict at base of vesicle to pinch it off
51
receptor mediated endocytosis by coated veesicles
clathrin can be stalled by tension and large cargo high mem tension
52
coats and gtpases
specific gtpases recruit protein effectors to membrane arfs sar1 rabs dynamin anchored by myrisolated N terminal tails coats help budding
53
coat type controls sorting and delivery routes
copII from er to ergic --sarI CopI form TGN tback to ER - Arf1 clathrin Arf1, dynamin from TGN to endosmes lysosomes endocytosis and from endsomes to lysosomes
54
snare proteins
transmembrane snare protiens in vesicles - v-SNARE interact specifically w target snares t-snares fuse together to bring bud in and have cargo protein delivered charged head groups dont want to fuse so SNARE is a tethering protien intertiwining brings mems close fusion requires lipid bilayers within 1.5 nm of each other water is removed between mem
55
botox
prevents secretion of neuromuscular junctions causing muslces to relax botox destroys snares so vesciles cant secrete so muscles can relaz bc vesicles have synaptic signals that orignally make msucles contract destroy proteins that mediate snare interaction botulinum toxins are protesases that cleave molecules invovled in synaptic transmission type a toxin = botox
56
location and morphology of the golgi apparatus in animals
er everywhere golgi around nucleus bc around nucleus is centrosome molecular motors on microtubles microtubules are poluar structures that make sure golgi is near nuclear
57
effects of microtubules
depolymerization on the distribution of the golgi apparatus micros are dependent on localizationof the golgi relocalization of golgi in absense of microtubules
58
REORGANIZE GOLGI DURING MITOSIS
IN PROPHASE DEPOLYMERIZE MICROTUBULES MITOSIS SPREAD THE GOLGI UNTIL DIVISION AND REASSEMBLE AFTER
59
PROTIEN TRAFFICIKING PATHWAYS THROUGHT THE GOLGI
golgi functions -carb processing protein sorting sphingomylein and glycosphingolipid synthesis mem changes vesicles made by codamers next compart uses diff codamerm
60
movign from er to golgi
MT mortos move transport vesicles from VTC to the golgi and fuse at cis faace
61
mem trafficiking
cells w a temp sensitive mutation in ER export process express a gfp viral mem protein fusion cells are at the restritive temperature at the start, causing accumulation of protein in ER when temp lowered transported can be followed
62
lysosomal targeting
low ph organelle soluble enzymes recog - break down everythina dn work at low ph -phosphorylate N linked mannose sugars rego by man 6p receptor intgegral mem protein --> temrinal phosphase then go to lysosome on end of sugar recog by adaptors pH sensitive release in lysosome recycled to golgi pH gradient created by F type ATPase lysosome is folded before relaizing right pH
63
glycoproteins with mannose 6p chains are transported to lysosomes
acidic organelles w a wide variety of hydrolases invovled in the breakdown of endocysoed substances and turnover of organelles membrane contains transporters for metabolites and proton pump
64
endoosmes to lysosomes
lysosomes are invovled in digestion of phagoctosed substances and the turnover of organelles by autophagy autophagy brings it to lysosome for degradation sometimes mit or other organelles warn down lysosmes become enlarged in lysosomal storage diseases such as Tay sach and Gaucher disease caused by deficinceies in lysosomal hydrolases
65
3 pathways to distribute integral mem proteins to the aprical or basolateral plasma mem
lipid raft lysosome sorting endosome glucose tranpsorters by sodium gradient pump directing to right place all proteins go to proper location
66
transgolgi
secretory proteins sorted by regulated and constitutive secretion in the trans golgi constitutive secretion involved in half life regulated secretion - reg by ligands ex collagen
67
cels take up low density lipoproteins LDLs by receptor mediated endocytosis
bad cholestrol cells package cholestrol in ldl b100 molecules bind to surface receptors on cells abt size of virus
68
atthersclerosis
causes hafl of all death in us cholestrol accumulates in artial walls forming plaques from LDL that circualtes in bllood more ldl the more rapid it develops ldl receptor carries cholestrol to cell has hydrophili coating of phopholipid and apoprotien B 100 that allows it to dissolve in blood statin -drug that blocks sytnhesis of cholestrol
69
cell pathway
after ldl deliverted to lysosome digestive enzymes break down exposing cholestryl ester core cells recyle it to surface of mem cholestrol metabolism controled by amount of cholestral liberated from ldl clatherin uncoated and goes to endosome break down into free cholestrol
70
coated pits form t mem
invaginate, vesicualte antibodies to the ldls are labelled with ferritin particles endosomes funtion as sorting points for lysosomes or recyling
71
dealing with substance coming in from outside
taken up by receptor mediated endocytosis or phagocytosis sorted in endosomes molecules in endosomes sorted to the lysosome or for recyling
72
how protiens are sorted after pasing through golgi
sorted for secretion or lysosomes in transgolgi - mannose 6 p receptor recog acid hydrolases and concentrate these into clatherin coated vesicles mem proteins and some proteins are constitutively secreted proteins for regulated secretion are conc by cargo receptors into dense clatherin coated vesicles
73
endocytostic pathways
specialized phagocytic cells ingest large particles fluid and macromoleucles are taken up by pinocytosis receptor mediated endocytosis provides a speficic route into anima cells enxocytosed macromolescules are sorted in ensomes lysosomes are the principla sites of itnracellular digestion
74
different types of modes of endocytosis
cells can send out arms of memberane that grabs water diff type of caot in capilaries called caveolae phagocytosis - big things get in
75
MECHANISM OF PHAGOCYTOSIS
ATTACH ENGULF FUSON PATHOGENS RESPOND CAN DO BC OF ACTIN NETWORK CREATED PHAGOSOMES
76
CAVEOLAE
IN CAPILARIES COATED W CAVEOLAE BIG AMOUNTS OF ENDOCYTOSIS COMPARISON OF LIPID RAFTS AND CAVEOLAE
77
MEM TRAFFIC ALONG THE ENDOCYTIC PATHWAY
SOME TO ENDOSOME SOME FROM ENDOSME TO SURFACE DIRECTY RECYCLING PERIPHERAL CYTOPLASM INDIRECT RECLYING PERINUCLEAR CYTOPLASM MAJORITY RECYLED TO PLASMA ME 2-20% INTERNALIZED CONTENT SORTING ALONG PATHWAY - WORKS BC OF GTP BINDING PROTEINS EX RABS
78
PH GRAIENTS
LIGANDS BIND AT AS A FUNCTION OF pH PH GRAIENTS ARE ALONG PATHWAY
79
ENDOCYTIC PATHWAY
RECYLING DEGRADATION TRANSCYOSIS
80
entry of viruses
escape endocytic vesicles lysteria - escapes mmigrates around cell and pushes out to invade neighboring cells
81
cellular degradation
lysosomal-- integral mem proteins orgnalles, long lived cytoplasmic proteins most cellular protein turnover many diseases prteosome -short lived cytoplasmic proteins in er autophagy - damaged organelels allow for compartmentalizated degradation adn regualtion
82
four stages of autophagy
recylce macromolecuels when nutrients is limiteed envelopment sealing merge w lysoome resulting residual body
83
tages of autophagy
allows cells to recule macromolecules when nutrient limited envelopment sealing mergin w lysosome resulting resdiual boddy recog damaged organelles and agregates of misfolded proteins
84
structures of protosomes
not mem boud organelles prtoein machiens only tagged proteins brought to protosmes like cyclin degraded down to aa and peptides resused parts: receptor, mortor, 6 subunits, cutting enzymes, detect tage, remove teg, prep for unravel and cut into segments
85
ubituitin
a polypeptide tagging proteins targeting seq reconvized by ubiquitin lygase puts U onto protein breaks down into substrates
86
degradation of cytoplasmid prtoeins
diff proteins have diff halflives must remove misfold and damage proteases break down peptide bonds use large protein complex w localized proteases nonspecific- autophoagosomes specific - proteosomes need U for protesome to recognize

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