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81 Cards in this Set
- Front
- Back
3 Major Cytoskeletal Proteins |
~Microfilaments ~Microtubules ~Intermediate Filaments |
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Cytoskeleton |
filamentous protein network involved in formation of cell shape, organization, and motility that is attached to cell membrane and organelles |
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Microfilaments |
made of an actin subunit that enables cell membrane organization, (muscle) contraction, and cargo transport |
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Microtubules |
made of tubulin subunits; serves as a framework for organelles, structural support for flagella/cilia, mitotic spindle |
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Intermediate Filaments |
used for structural support for nuclear membrane, integrity of cells in tissues, and barrier functions in skin, hair, nail |
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Steps of Polymerization of G-actin |
-Nucleation -Elongation -Steady State |
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Critical Concentration (Cc) |
the concentration of monomers in equilibrium with filaments (dissociation and association of subunits are at the same rate); also known as a steady state |
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Treadmilling |
a form of actin filament assembly in which subunits flow through the filament |
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What regulates the rate of assembly and disassembly of actin subunits? |
Actin-binding proteins |
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Profilin |
enhances the exchange of ADP for ATP on G-actin; facilitates actin filament assembly |
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Cofilin |
enhances the rate of loss of ADP-actin from filament (-) end; disassembles the filaments |
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Thymosin-b4 |
binds ATP-G-actin to provide a reservoir of actin for polymerization |
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CapZ |
a capping protein that binds to the (+) end and blocks actin filament assembly and disassembly at the (+) |
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Formin FH2 domain |
a donut-shaped dimer that is used as a means for actin nucleation in unbranched filaments
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What event activates the formin protein? |
Binding of Rho-GTP to the Rho binding domain of the formin protein |
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Arp2/3 Complex |
used for actin nucleation that results in a branched conformation present in motile cells; this is done by binding of the complex to an actin filament and WASp |
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What event activates the WASp? |
Binding of membrane-bound Cdc42-GTP to the rho binding domain and exposing of the acidic domain |
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Dystrophin |
a protein that keeps the structural integrity of muscle cells; defective dystrophin results in death of muscle myofibrils |
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Myosins |
actin-based motor proteinspowered by ATP hydrolysis to move along the (+) end of actin filaments |
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Myosin I |
used in membrane association and endocytosis |
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Power Stroke |
a term used to describe the release of elastic energy and Pi from a myosin head that causes the head to straighten and the actin filament to move to the left |
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Structure of Skeletal Muscle Sarcomere |
consist of muscle fibers made of bundles of multinucleated cells which contain a bundle of myofibrils which consist of thousands of sarcomeres |
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CapZ |
stabilizes the actin filaments by capping the (+) end of the thin filaments at the Z-disk |
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Tropomodulin |
stabilizes the actin filaments by capping the (-) end of the thin filaments at the Z-disk |
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Titin |
a giant protein that extends through the thick filaments and attaches to the Z-disk |
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Nebulin |
binds actin subunits and determines the length of the thin filament |
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Troponin (Tn) |
a club-like protein complex that is bound to the long alpha-helical TM molecule |
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Sarcoplasmic Reticulum |
a specialized ER structure in muscle cells that regulates the level of free Ca2+ in myofibrils |
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Ca2+ dependent thin-filaments regulate...? |
skeletal muscle contraction |
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Myosin ATP Hydrolysis: EXPLAIN! |
Good job you! Explaining stuff! (see notebook paper entry) |
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Sliding-Filament Model: EXPLAIN! |
Good job you! Remembering ****! Hooray! (see notebook paper entry) |
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Ca2+ Dependent Thin-Filament Regulation: EXPLAIN! |
Skeletal muscle contraction. YOU TELL 'EM! (see notebook paper entry) |
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Thick-Filament Regulation: EXPLAIN!!! |
Smooth muscle and non-muscle cell contraction. YAAS! |
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What is the job of the endocytic pathway? |
-Take up cholesterol carried in LDL -Take up iron atoms carried by transferrin -Remove receptors from cell surface to downregulate activity |
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How does the coat protein recognize the soluble coat proteins? |
they are recognized indirectly via the membrane cargo-soluble cargo complex |
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What is the role of coat proteins in vesicle fusion and budding? |
they determine which proteins are admitted into the vesicle and they give curvature of the membrane |
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What vesicle type(s) are used for ER to cis-Golgi transport? |
COPII |
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What vesicle type(s) are used for cis-Golgi to ER transport? |
COPI |
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What vesicle type(s) are used for later to earlier Golgi cisternae? |
COPI |
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What vesicle type(s) are used for trans-Golgi to endosome? |
Clathrin and adapter proteins |
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What vesicle type(s) are used for plasma membrane to endosome transport? |
Clathrin and adapter proteins |
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What vesicle type(s) are used for Golgi to lysosome transport? |
Clathrin and adapter proteins |
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How are G proteins (GTPase) activated? |
They are switched between active and inactive states by binding to GTP (active) or GDP (inactive) |
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Sar1 |
a G protein that serves as a binding site for coat proteins; it recruits cargo proteins which leads to polymerization of the coat proteins |
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What proteins are involved in COPII coat assembly and disassembly? |
-Sar1 -Sec23 |
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v-SNARE |
the protein present on vesicles that is recognized by t-SNARE on the target membrane |
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KDEL |
located on ER-resident soluble proteins and paired with a receptor in the cis-Golgi membrane; COP1 vesicles |
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Mannose 6-phosphate (M6P) |
present on soluble lysosomal enzymes and targeted to the trans-Golgi membrane; Clathrin/AP1 vesicles |
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Di-acidic |
present on cargo membrane proteins in ER and target the COPII Sec24 subunit (export from ER); COPII vesicles |
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Cisternal Maturation |
Anterograde passage and loss of enzymes that eventually transform compartments into it's previous compartment; e.g. trans golgi donating enzymes to medial Golgi, medial to cis, etc. |
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Regulated Secretory Vesicles |
proteins that selectively diffuse with the presence of a signal that can come in the form of a neural or hormonal signal or protein aggregation |
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Familial Hypercholesterolemia |
a disease caused by a defection in the endocytosis of LDL which leads to increased cholesterol in the blood |
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What are the 3 pathways for delivery of materials to lysosomes? |
-Phagocytosis -Endocytosis -Autophagy |
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Endocytosis |
Soluble macromolecules (or membrane proteins) from outside the cell are pinched inward by the membrane, forming endosomes. The resulting endosome then fuses with a primary lysosome |
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Phagocytosis |
Large, insoluble particles are engulfed by the cell membrane, creating a phagosome. The phagosome then fuses with a primary lysosome |
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Autophagy |
A fragment of a membrane bound organelle surrounds organelles or cytosolic proteins creating an autophagosome. This fuses with a primary lysosome resulting in a secondary lysosome. |
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What type of actin filaments does Formin nucleate for? |
unbranched actin filaments |
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What type of actin filaments does Arp2/3 complex nucleate for? |
branched actin filaments |
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Myosin V |
a motor protein that functions to transport organelles toward the (+) end of actin filaments |
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Cc+ of monomeric G-actin |
the critical concentration at which actin polymerization reaches a steady state; above this concentration there is net growth at the (+) end |
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What protein is the direct target of Ca2+ in skeletal muscle contraction? |
Troponin |
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What protein is the direct target of Ca2+ in smooth muscle contraction? |
Myosin LC kinase |
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What is caused by interaction of Ca2+ with troponin? |
myosin binding site on actin filaments are exposed |
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What is caused by interaction of Ca2+ with myosin light chain kinase? |
Myosin becomes unfolded and myosin filaments are assembled |
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During muscle contraction, to which end of the actin filament does the myosin head walk?
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Plus end |
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To what structure in sarcomeres does the actin filament connect? |
Z disk |
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What type of cargo proteins carry the KDEL sequence? |
ER-resident soluble proteins |
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What type of cargo proteins carry Mannose 6-phosphate sorting signal? |
Soluble lysosomal enzymes |
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What type of cargo proteins carry the di-acidic sorting signal? |
membrane cargo proteins in the ER |
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What type of vesicles move cargos with a KDEL sequence? |
COPI |
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What type of vesicles move cargos with a Mannose 6-phosphate signal? |
Clathrin/AP1 and Clathrin/AP2 |
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What type of vesicles move cargos with a di-acidic signal? |
COPII |
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What route transports cargos bearing a KDEL sequence? |
cis-Golgi to ER |
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What route transports cargos bearing a Mannose 6-phosphate signal? |
1) trans-Golgi to endosomes 2) cell surface to endosomes |
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What route transports cargos bearing a di-acidic signal? |
ER to cis-Golgi |
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What materials are taken up in autophagy in response to stavation? |
cytosolic proteins and organelles |
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What is the main protein involved in the expansion of the membrane on the vesicles? |
Atg8 |
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Are vesicles involved in the endocytosis of LDL particles fused with ensosomes/lysosomes? |
yes |
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Are vesicles involved in autophagy in response to starvation fused with ensosomes/lysosomes? |
yes |
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What are the biological functions of endocytosis of LDL particles? |
LDL particles are broken down by lysosomal enzymes, releasing cholesterol for use by cells |
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What are the biological functions of autophagy in response to starvation? |
Materials taken up are degraded by lysosomal enzymes, generating small molecules for use as nutrients by cells |