Term
The cytoskeleton consists of three types of cytosolic fibers, Name them |
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Definition
Microfilaments 7-9 nm (diameter) Intermediate filaments 10 nm Microtubules 24 nm |
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Term
What is the diameter of: microfilaments intermediate filaments microtubules |
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Definition
Diameters: Microfilaments 7-9 nm Intermediate filaments 10 nm Microtubules 24 nm |
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Term
| Cytosolic fibers are made up of what? |
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Definition
| they are polymers of small proteins held together by non-covalent bonds |
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Term
| Name two modes of movement involving cytosolic fibers |
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Definition
1. Motor proteins use ATP to slide along microfilaments and microtubules 2. Assembly and disassembly of microfilaments and microtubules (Windors had people stand along the wall and go from the back of the line to the front to simulate movement) |
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Term
| Microfilaments are synonymous with what protein? |
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Definition
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Term
| What action of actin (aka microfilaments) causes cell migration? |
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Definition
| The dynamic change known as assembly and disassembly. |
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Term
| What is the most abundant intracellular protein? |
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Definition
Actin! Making up to 10% by weight in muscle cells (Collagen is most abundant outside of cell) |
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Term
| Is ATP required for the polymerization of G-actin into F-actin? |
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Definition
No, In a solution of Na+, K+, or Mg++ globular actin (G-actin) will polymerize into Filamentous-actin (F-actin). Polymerization is reversible! However the kinetic will be affected! |
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Term
| What did Windsor refer to as "Spot Welds" that hold actin fibers together in bundles? |
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Definition
Cross-linking proteins (fimbrin, alpha-actinin, filamin, spectrin, and dystrophin) |
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Term
Duchene muscular dystrophy (DMD) is caused by an defect in what actin cross-linking protein gene? |
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Definition
a defect in the dystrophin gene Results in muscle cells not being supported by cortical cytoskeleton |
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Term
| What are the 3 phases of actin polymerization? |
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Definition
1. Nucleation- Lag period where G-proteins aggregate to act as seed 2. Elongation-addition of monomers to the nucleus at both ends 3. Steady state- monomers exchange but there is no net change in filament length. |
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Term
| If nuclei are added, what step of actin polymerization is skipped? |
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Definition
The first step 1. Nucleation This means there is NO lag phase while G-proteins aggregate |
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Term
| In actin polymerization, which end elongates faster? The positive (+) or negative (-) end? |
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Definition
| The positive (+) end elongates at about 5-10 times faster! |
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Term
In actin polymerization, what is the Critical concentration (Cc) for the positive and negative ends? |
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Definition
Critical concentrations: positive (+) .12 Micro Mole negative (-) .6 Micro Mole Cc is also dependent on ATP or ADP binding. If bound to ADP, the rate of elongation is characteristic of the negative (-) end! |
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Term
| How do cytochalasin and Latunculin stop actin polymerization? |
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Definition
cytochalasin binds to the positive end (+) of F-actin and blocks addition of more subunits. Latrunculin binds G-actin and inhibits it from adding to the filament. |
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Term
| How does phalloidin (angel of death mushroom) alter actin monomer-polymer equilibration? |
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Definition
| Phalloidin binds between the subunits in F-actin and locks the subunits together. Prevents depolymerization. |
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Term
| How does Jasplakolinode alter actin monomer-polymer equilibration? |
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Definition
It shifts equilibrium to F-actin |
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Term
| How does regulation of actine polymerization occur? Name 3 examples |
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Definition
Regualtion occurs by proteins that bind G-actin or F-action 1. Thymoisin Beta 4- actin sequestering protein that binds ATP-G-actin. INHIBITS ASSEMBLY! 2. Profilin- binds ATP-G-actin and promotes assembly of F-actin. Promotes ATP Binding 3. Cofilin- binds to F-actin and breaks the filament into short pieces. |
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Term
Name the 3 proteins that cap the + end of actin. |
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Definition
1. Severin-severing and capping 2. Gelsolin-severing and capping 3. CapZ capping protein |
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Term
| Name the 3 proteins that cap (-) end of actin |
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Definition
Cofilin- dissociation from (-) end Tropomodulin- capping (-) end Arp2/3 complex capping (-) end and PROMOTES BRANCHING! |
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Term
| What is the sequestering "you can't play anymore" protein that inhitibits actin polymeration. |
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Definition
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Term
| This protein is involved in actin polymeration and binds opposite of the ATP-binding cleft thus catalyzing the exchange of ADP for ATP. |
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Definition
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Term
| In cell movement what are described as the motor, fuel, and tracks. |
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Definition
motor-myosin fuel-ATP tracks-actin |
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Term
| What are the two most abundant types of Myosin? |
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Definition
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Term
| What Myosin powers muscle contraction and cytokinesis? |
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Definition
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Term
| Myosin I and V play a role in what? |
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Definition
| cytoskeleton-membrane interactions |
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Term
(T/F) the neck region of Myosin is rich in glycine and proline. |
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Definition
FALSE! The neck region is alpha-helical and remember that glycine and proline are alpha-helix breakers! |
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Term
| What domain of myosin contains the ATP and Actin binding sites? |
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Definition
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Term
| Where on myosin are the 'light chains' located? |
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Definition
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Term
| What element regulates all myosins? |
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Definition
Calcium Differences in light chain makes their responses different. |
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Term
| How many steps does myosin take per hydrolyzed ATP? |
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Definition
ONE STEP PER ATP! They move in discrete steps (5-10 nm) per ATP |
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Term
| Does myosin move in a "hand over hand" or "inchworm fashion"? |
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Definition
| HAND OVER HAND! Much faster |
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Term
What are the functional units of skeletal muscle? |
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Definition
| Skeletal muscles>bundle of muscle fibers>Myofibers>myofibrils>sarcomeres |
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Term
| What makes muscles elastic, like a rubber band? |
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Definition
It is due to titin, which connects the ends of myosin to the Z-disk. Nebulin forms non-elastic filaments from the Z-disk along the actin filaments. |
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Term
| What initiates muscle contraction? |
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Definition
Nerve impulse at NMJ leads to opening of voltage-gated calcium channels in SPR. The increase in cytosolic Ca2+ concentrations (chemical) initiates contraction (mechanical) SPR= sarcoplasmic recticulum |
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