where are the rRNA’s synthesized? do they belong here? how do they get transported?
in nucleolus, they transport out back to the cytosol via nuclear pores
what is the purpose of lamins?
support and structure, they attach to the nuclear pore complexes on the inner membrane surface (nucleus) and bind many proteins
what forms the nuclear pores?
describe the structure of a nuclear pore:
nuclear pore complex, contains 8 filaments forming a basket (nuclear side) with cytoplasmic filaments
why does this process of import/export not need energy input?
it operates on a [ ] of RAN-GTP-importin (cytosol) and [ ] of importin-cargo complex via GEF and GAP
note: that GTP is associated with ribosomes and cotranslational translocation and ATP is associated with post-translational
what are the 5 principle modifications that occur with ER synthesized proteins before reaching a destination and where do they occur?
2) disulfide bond formation
4)assembly of multimeric proteins
what is glycosylation? what types are there?
why is it crucial for some proteins to have sorts of glycosylation?
addition of a carbohydrate chain to O (serene or threonine) or N (asparagin)
crucial for proper folding and stability
what is the role of disulfide bonds?
how do disulfide bonds form?
to stabilize 3 and 4 protein structures, formed via PDI
where are disulfide bonds formed in the cell?
in secretory or exoplasmic domains of proteins (i.e. free rib. proteins do not have this)
what is an anterograde vesicle?
one moving towards cell surface
what is an retrograde vesicle?
moving into the cell
what drives the budding of a vesicle from the Golgi?
what function does the vesicle coat serve?
polymerization of protein complexes to form the vesicle coat
adds curvature to vesicle and is selective to vesicle contents
what initiates budding?
first, the recruitment of GTP-binding proteins to donor membrane which control the coat assembly
what are coat proteins? and the cargo-receptor protein?
coat proteins: multimeric large proteins that hide the vSNAREs
cargo-receptor protein: coat protein attracts them to allow vesicle to carry soluble proteins
explain how GTP-binding proteins initiate budding
: conformational change in the protein when bound to GDP—>then GTP can allow protein N-hydrophobic tail to extend into the membrane, when attached to the
:once these proteins are in the membrane, the coat begins assembly by binding to these GTP binding proteins + buds off
: hydrolyzing of GTP back to GDP and then the arm retracts out of the membrane and the coat falls off with the GTP binding proteins
how do the vesicle buds discriminate between the membrane and those as cargo?
binding to sorting sequences found within the cytosolic domain of cargo
what targets the vesicle to thier destination?
what converts rab-GDP to rab-GTP to be able to interact with the surface protein for anchorage?
a GEF converts it from GDP to GTP to interact with the RAB effector
what causes dissociation of SNARE complexes after membrane fusion?
ATP hydrolysis with a cytosolic protein
what is retrograde transport? and what molecules does it occur with?
how are SNARE complexes reused?
vesicle heading towards a cell
occurs between cis-golgi and ER (BIP, PDI also return this way), SNARE is returned with a signal sequence on the N-terminus
how does endocytosis facilitate bacterias?
via phagosytosis, where the plasma membrane envelopes the material, a non-selective actin mediated process
what is receptor-mediated endocytosis?
where a specific cell surface protein binds to a macromolecule ligand and then pinches off the membrane containing it (i.e. LDL, ferrotranferrin )
what is the rate of ligand internalization dependant on?
the amount of receptors on the cell surface
where and how does the receptor make way back to the plasma membrane?
in the late endosome, it dissociates and is recycled back
why does LDL have a mono lipid layer instead of a bilayer?
inside the molecule is highly hydrophobic
what is the appx number of endocytosed proteins on a cell surface?
appx 1/2 of all cell surface proteins per hour
why does the propeller on the LDL receptor have an increased affinity for the ligand binding arm at a lower pH? how
does this work with the system of endocytosis?
the propellor gets a + charge at low pH due to histidine and it attracts the - binding arm
what is the process of LDL budding?
binding receptor arm around the ApoB protein, and receptor recruits the blue and red coat protein
** coat protein provides curvature to allow for the budding, also GTP binding proteins are encouraging the recruitment as well. then endocytic buds
vesicle has GTP hydrolysis to GDP and the coat protein and GTP binding proteins are all released to allow for the V-snare reveal to interact with the t-snare on the late endosomes + RAB-GTP to interact with the RAB effector dock
***RAB-GTP interactions allow for SNARE interactions to bring membranes close for fusing light
what is transferrin? what is ferrotransferrin?
a glycoprotein in the blood to transfer iron to cells form liver and stomach, the 2 bound Fe3+ ion version
when does ferrotransferrin bind to it’s receptors the most? and what does this induce?
at a neutral p
H, this induces endocytosis
explain how the receptor-apotransferrin complex gets back to membrane
endosome low pH releases ions (converts to 2+ ion so it can exit endosome) then the receptor bound will undergo budding like normal NOTE: LDL would be released here from its receptor
why, in trancytosis, would the Fc region on the antibody be recognized?
Fc region on the antibody is recognized because Fc is constant in a class
(can therefore recognize any antibody with Immunoglubulin class G sequence)
therefore is the most efficient
why does the vesicle not go through the late endosome instead of the other side of the
-V-SNARE will only recognize the T-SNARE on the membrane of the cell
note: cotranslational has GTP and ribosome
post-translational has ATP and BIP
for any STA, where will the +++ charges be located?
on the cytosolic side
which transmembrane protein has a signal sequence?
what controls protein levels in the cell?
proteins ultimately, (regulatory proteins, controlled by gene transcription, controlled by proteins) and their interactions with surface proteins
what types of signal molecules are there?
extracellular ones that
a) bind to receptors on plasma me,brane
b) bind to transcription factor
how are intracellular receptors activated on transcription factors?
when they are bound to their lipid soluble ligand hormones
note: type 2 extracellular signal molecules must be mostly hydrophobic but partly hydrophilic to get through membrane
describe the nuclear receptor for hormones (similarities and differences) for the 3 functional regions
N: unique, and determines the function, different
Z: binds to DNA, similar
C: binds to ligand to turn off or on transcription, similar in hydrophobicity
how can a signaling molecule interact with receptors but never enter the cell?
by causing a conformational change on cytosolic side of receptor to induce an action (: phosphoralation is crucial )
notes: cell surface receptor will intract with a ligand (non-soluble therefore can’t get thru membrane) then will inhibit function or gain one and this will pass on the signal to other cytosolic proteins
:all need NSL
: phosphoralation is crucial to cause a conformational change to expose NLS (nuclear localization signal)
what is cross talk?
interactions between signaling pathways and the fact that there are multiple transcription factors per pathway
what are the different mamalian signaling? (3)
endocrine: longest distance
paracrine: affect close proximity
autocrine: secretions from self cause an action (tumor)
what responses arise from an external signal?
a change in activity or function of pre-existing proteins OR amounts produced
what is a major difference between receptors and signal molecules?
the receptor binds only 1 signal vs signals can bind to more than one receptor and activate different cellular responses
what is binding specifity?
receptor accepts a certain ligand
note: high binding specificity= accommodates only a small amount of substrates (ligands) of receptors to exhibit effector specificity
(mediates a specific cell response)
: that receptor has a high one vs the signaling molecule will bind to many different different receptor types
how are adrenaline and glucagon similar
they bind to similar G-protein coupled receptors in liver to synthesize cAMP to promote glycogen breakdown
describe the [ ] ligand vs max binding graph
graph: Kd: binding strength between the receptor+ligand...where receptor +ligand is in equilibrium with it’s RL complex similar to
Km but different, more like Keq= products/reactants, dependent on the receptor (low=high binding, high Kd=loose binding)
note: the more receptors, the less ligands we need because it is more sensitive vs less receptors where we need more ligands for it to recognize the ligand
what is the sensitivity?
regulation of the number of receptors for a signal molecule
: plays a role in directing events in the cell and can endocytose a receptor molecule via vesicles AND decreasing the receptors this
way will prevent further signaling! (result: SHUT IT DOWN via endocytosing)(this is the rate-limiting step)
what is a way the cell regulates the number of receptors for a signal molecule?
endocytosis of the cell membrane
what types of hormones are there?
agonists: they mimic a natural hormone to signal a specific pathway (epinephrine and isoproterenol)
antagonists: bind to the receptor but acts as a blocker (epinephrine and alprenolol)
what is the difference between first messengers and second messengers?
1st: ligands binding to receptors on cell surface will cause increase (short-live) for 2nd
2nd: lead to the rapid change in activity of another cellular protein
what commonly functions as the activation domain on a hormone?
N region contains it, and the hormone binding domain near the C-terminus does too commonly (though here it can be there repression domain as well)
what type of forces complement the ligand and the receptor?
what is respiratory control?
controlling the ADP and ATP in the mitochondria to regulate ATP synthase production
what prevents the alpha-beta units from turning when the wheel turns?
the b and other subunits on the F0 complex
how is adrenaline a paracrine and endocrine signal?
paracrine: acts as a neurotransmitter by neurons
endocrine: secretion by adrenal glands result in it being a systematic affecter
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