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51 Cards in this Set

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"Free ribosomes" Where does translation always begin?
ribosomes floating in the cytoplasm performing translation. Translation of free ribosomes always begins in the cytosol
membrane bound ribosomes found where? how to they know to go there?
on RER outer surface. there is a targeting sequence on the N terminus telling them to go to the RER
Where are proteins/cargo carried in vesicles?
carried inside the vesicles, but also on/in the membrane. Can be on the inner/outer/or transmembrane.
Network of enclosed tubules with continuous lumen, continuous with nuclear envelope, largest membrane system in mammals
Endoplasmic recticulum-continuous SER/RER lumen
Secretory Pathway of RER
mRNA-Translating ribosomes-RER-Golgi-Secretory vesicles-Exterior
How do you get a protein into the RER? What is the pathway called? Envisions the steps.
Secretory Pathway (of RER)

-signal sequence on N terminus of growing polypeptide (first 16-30 nucleotides) is bound to by Signal Recognition Particle (SRP-6 proteins/1RNA)

-Binds to Signal sequence and stalls elongation
-Brings polypep to SRP receptor on surface of RER
-Binding triggers release of SRP (GTPase dependent)
-Translation starts again, threading the polypep through the translocon into lumen on the RER
-cleaved by signal peptidase at amino terminus=secretory protein
Integral Membrane Protein Types
Stop Transfer Sequence (STS) and Internal Signal Sequence (ISS)
Stop Transfer Sequence
Translocation of STS and threading when translocon recognizes a membrane-spanning domain

-stops translation and releases the polypep into the RER membrance

-translation then continues and the signal sequence removed by signal peptidases
Internal Signal Sequence
when signal sequence is located further down the polypeptide/not near the N terminal

-"internal" means inside the polypeptide, causes a switch in the C and N terminals in lumen/cytosol
Multi-Pass Proteins
alternating ISS and STS due to multiple sequences in polypeptide. leads to looping of polypep (pp) in and out of the membrane

you can tell which region are hydrophobic by the hydropathy profile/graph
N-linked Glycosylation is what?
adding a sugar (oligosacc) to dolichol on inner membrane of RER
Glycolipid modification to RER
add glycolipids to inner membrane of RER (GPI Anchors)

-GPI anchors secreted into vesicles (inner membrane) then fuse with plasma membrane-located on the outside (remember diagram)
Protein Folding in RER via Chaperones. What are they? function? examples?
Chaperones assist in proper folding of proteins into correct tertiary structure.

ex) BiP (Hsp) and Calnexin/Calretiiculin
What is Protein Disulfide Isomerase? what does it do?
enzyme in lumen of RER that catalyzes correct formation of disulfide bonds btw cys residues. Critical for proper protein folding.
Chaperones act as sensors for ?
misfolded proteins
Name/describe the 2 ways misfolded proteins can be fixed in RER
ERAD- misfolded proteins transported to cytosol for degradation by ubiquitin-proteosome system

Unfolded Protein Response-Stress response triggered by overload of unfolded proteins, Kinase pathwas says "stop making proteins!"
Smooth endoplasmic reticulum is usually located in what kind of cells?
sparse in many cells but abundant in cells involved in metabolism of lipids such as steroid hormone producing cells and the sarcoplasmic reticulum
Main Function of SER
Synth of Lipids (on cytosolic side)
Calcium Storage/Release (SR)
Glycogen metabolism (Glucose 6-phosphate in liver SER)
Drug Detoxifcation (Liver)
Synthesis of Lipids in the SER: makes what and where on the SER?
makes phospholipids, cholesterol, ceramide on the cytosolic side of the SER via cytosolic enzymes. They are built into the outer leaflets of SER and flippasses bring them inside
Flippases do what?
switch lipids onto the other side of a membrane
Golgi structure/nickname
"Fedex", stacks of cisternae=membrance bound sacs that transport vesicles
has cis network/medial network/trans network

-cis=convex/toward nucleus/entry face
-trans=concave/exit face
Function of Golgi
Protein Processing
Cis Golgi Network does what? TEST DAY
phophorylation of N-lnked Oligosacc(which is made in the ER), with mannose-6-phosphate (which tags proteins to go to lysosomes to help digest stuff)

shipped to Golgi, while moving thru golgi, enzymes remove mannoses and add other residues ="Trimming decorating of xmas tree)

(mannose 6-phosphate)
Golgi Cisternae do what? TEST DAY!
Modify N-linked Oligosacc by:
-removal of mannose
-addition of residues and addition of O-linked Oligosacc
trans golgi network does what?
sulfation of proteins on tyrosine
Phosphorylation of N-Oligosaccarides tags proteins to go/become what?
tags proteins to go to lysomes and become lysosomal enzymes.

mannose is tagged by phosphate
O-linked gycosylation of Proteins. TEST DAY!!!
Sugars are added to Ser, Thr, or Tyr
-added one at a time in the cis/medial cisternae

"O"ne at a time. added to ser-thr. Tyrosine.
Sulfation of proteins in Golgi
sulfate group is added to Tyr residue
-occurs mainly in trans Golgi network
Synth of Sphinomyelin and Glycolipids
synthed from ceramind in lumen of golgi-move to organeeles via budding of vesicles
Types of Secretion from the Golgi (3 types)
Constitutive, Regulated Secretion, Lysosomal
Consitituive Secretion from Golgi
constantly on/secreting things the cell always needs/is making ex) ECM or basal lamina
Regulated Secretion from Golgi
vesicles only released in response to stimulus
ex) neurotransmitter

-exits golgi via clatherin-coated vesicles to for immature secretory granules

-excess membrane recycle+concentrated cargo in as little membrane as possible

exocytosis via specific signals/stimulus
Lysosome pathway
Lysosomal enzymes tagged with mannose 6 phos and exit the trans golgi via budding of clatherin coated vesicles
Vesicular Trafficking has what kinds of transport?
Anterograde (COPII) and Retrograde (COPI) vesicles
the messy COP (hutch)

goes from RER to cis golgi or tubular vesicles network (anterograde/spreading out)
the neat cop (starsky)

trans to cis golgi vesicles to RER (retrograde/cleaning up)
Clatherin-coated vesicles
transport in both directions btw the trans golgi and other cell compartments
Budding of Transport Vesicles: transmembrane proteins contain specific AA sequence that functions as a _______ for ______ and _____
sorting signal for retention and export
Transport vesicles bud from membranes as...?
coated vesicles
what binds to sorting signals and the coat during vesicles budding?

what do they do?
adaptor proteins

they couple the transmembrane protein to the protein coat of the budding vesicle
Adaptor proteins are _____ proteins
Dynamin is/does what?
GTPase that pinches off the budding transport vesicle
Activity of adaptor proteins is regulated by? give 2 examples
GTP binding proteins ex) ART and Rab
After the transport vesicle buds off into cytoplasm, the coat ______ so that?
dissolves so that the vesicle can recognize/fuse with correct target membrane
Receptor on PROTEIN that connects to clatherin coat through adaptor protein.

used to mark what?
Mannose 6-P

lysosomal enzymes
What has to happen to expose proteins on the surface of the transport vesicle?
the coat+adaptor proteins have to be dissolved
Vesicular Fusion: What is recruited to membrance and interacts with the effector proteins?
Name the 2 proteins used on the surface of vesicular fusion and their function
v-SNARE (vesicle specific protein) and t-SNARE (target specific protein)

get tethered together to help facilitate fusion
What does the effector protein do during vesicular fusion?

What results of this action? byproduct?
it finds the targeting receptor, binds to it, and tethers the SNARE proteins together as a result. This leads to the GTP hydrolysis and membrane fusion
How many membranes does a protein pass after translation?

secretory protein technically is always inside one membrane or another all the way through sorting until it is secreted into the Extracellular space
Secretory Granules follow what type of export system? what do they look like?
same system as export of vesicles. look like "bullseyes"