Molecular Test 2 Review Flashcards
What is the function of tight junctions?
Seals gap between epithelial cells.
What is the function of adherens junctions?
Connects actin filament bundle in one cell with that in the next cell.
What is the function of the desmosome?
Connects intermediate filaments in one cell to those in the next cell.
What is the function of gap junctions?
Allow the passage of small water-soluble molecules from cell to cell.
What is the function of hemidesmosomes?
Anchors intermediate filaments in a cell to extracellular matrix.
What is the function of actin-linked cell-matrix adhesion?
Anchors actin filaments in cell to extracellular matrix.
Which cell junction type is a occluding junction?
tight junction
Which cell junction type is a cell-cell anchoring junction?
> adherens junction
> desmosome
Which cell junction type is a channel-forming junction?
gap junction
Which cell junction type is a cell-matrix anchoring junction?
> actin-linked cell-matrix adhesion
> hemidesmosome
Which three cell junctions form the junctional complex?
> tight junctions
adherens junction
desmosome
Which cell junctions do actin bind to?
> adherens junction
> actin-linked cell-matrix
Which cell junctions do intermediate filaments bind to?
> desmosome
> hemisesmosome
List the three anchor proteins that link classical cadherins to actin in the cytoskeleton?
> beta-catenin
gamma-catenin
p120-catenin
Which two cell types have cadherins as the principal components?
> adheren junctions
desmosomes
cluster at sites of cell-cell contract in most solid tissues
Classical cadherins?
Ca2+ dependent adherens junctions.
- E-cadherin
- N-cadherin
- VE-cadherin
- P-cadherin
Nonclassical cadherins?
Ca2+ dependent; form desmosome junctions, and the recently discovered large subfamily of protocadherins, which are implicated in neuronal plasticity
- desmocollins
- desmogleins
What are the two main tight junction proteins?
> claudin (main functional component)
> occludin
What protein anchors tight junctions to actin cytoskeleton?
ZO protein
List the 3 functions of tight junctions.
> barrier function
fence function
signaling function
What are the 3 conserved polarity proteins complexes that control polarization processes and maintain polarity?
> Par
Crumbs
Scribble
What does formin do?
nucleates assembly and remains associated with the growing plus end
actin subunit accessory protein
What does ARP complex do?
nucleates assembly to form a web and remains associated with the minus end
actin subunit accessory protein
What does profilin do?
binds to subunits, speeds assembly
actin subunit accessory protein
What does thymosin do?
binds to subunits, prevents assembly
actin subunit accessory protein
What does cofilin do?
binds ADP-actin filaments, accelerates disassembly
actin filament accessory protein
What does fimbrin, alpha-actinin, filamin, and EFM do?
filament bundling, cross-linking, and attachment to membrane
actin filament accessory proteins
What does tropomyosin do?
stabilizes filament
actin filament accessory protein
What does gamma-TuRC do?
nucleates assembly and remains associated with the minus end
microtubule accessory protein
What does kinesin 13 do?
enhances catastrophic disassembly at plus end
microtubule filament accessory protein
What does Tau and MAP-2 do?
filament bundling and cross-linking
microtubule filament accessory protein
What does MAPs do?
stabilizing tubules by binding along sides
microtubule filament accessory protein
What does XMAP215 do?
stabilizing plus ends and accelerates assembly
microtubule filament accessory protein
After the first round of low-speed centrifugation in cell fractionation, what does the pellet contain?
> whole cells
nuclei
cytoskeleton
After medium-speed centrifugation in the second round of cell fractionation, what does the pellet contain?
> mitochondria
lysosomes
perioxisomes
After high-speed centrifugation in the third round of cell fractionation, what does the pellet contain?
> microsomes
> small vesicles
After very-high-speed centrifugation in the fourth round of cell fractionation, what does the pellet contain?
> ribosomes
viruses
large macromolecules
ion-exchange chromatography
+ charge beads
gel-filtration chromatography
porous bead
affinity chromatography
bead with covalently attached substrate
Desensitization of Signal by hormone level dropping.
decrease AC activity -> decreased cAMP -> decreased PKA activity
Desensitization of signal by removing signaling molecule.
phosphodiesterases (remove cAMP/cGMP)
Desensitization of signal by receptor sequestration.
endosome
Desensitization of signal by receptor destruction.
endosome + lysosome (proteases)
Desensitization of signal by GRKs (G protein receptor kinases).
phosphorylate the receptor such that another protein called ARRESTIN will bind to the 3rd intracellular loop & prevents G-alpha from interacting with the third loop.
Result -> G-alpha-GDP does not get converted to G-alpha-GTP.
How does arrestin desensitization of signals?
Binds to 3rd intracellular loop and prevents G-alpha from interacting with the 3rd loop.
order of GPCR mechanism
GPCR -> trimeric Gs-protein -> adenylyl cyclase -> cAMP -> PKA -> enzyme -> substrate/product -> amplification
Gs GPCR
Gs -> adenylyl cyclase -> cAMP -> PKA
Gi GPCR
Gi -> inhibition of adenylyl cyclase -> no cAMP -> no PKA
Gq GPCR
Gq -> PLC (cleaves PIP2) -> DAG and IP3:
IP3 -> Ca2+ release -> binds to PKC and calmodulin -> activate proteins
DAG -> PKC -> phosphorylation of target proteins
Steps in RTK signaling.
1) growth factor binds and receptor dimerizes
2) autophosphorylation occurs
3) binding of adaptor proteins such as Grb2
4) complex assembly
5) guanine NT exchange
6) Ras binds to RAF and initiates MAP kinase pathway
