Term
| The cytoskeleton an intracellular protein network of...(3) |
|
Definition
| The cytoskeleton is an intracellular protein network of microtubules, microfilaments, and intermediate filaments |
|
|
Term
| Mechanoenzymes (such as myosin) that use energy from ATP to move |
|
Definition
|
|
Term
| Microtubules work in conjunction with what motor proteins? What motor protein does actin work in conjunction with? |
|
Definition
| Microtubules work in conjunction with Kinesin and Dynein. Actin works in conjunction with myosin. |
|
|
Term
| The 3 general ways that cells use the cytoskeleton for movement |
|
Definition
1.The cytoskeleton is the "road" and the motor proteins are the carriers
2.To reorganize the cytoskeletal network by pushing it forward like a bulldozer
3.Motor proteins pull on the cytoskeletal rope |
|
|
Term
| Microtubles are tubelike polymers of... |
|
Definition
| Microtubules are tubelike polymers of the protein tubulin |
|
|
Term
| A multiprotein complex near the center of the cell from which microtubules grow |
|
Definition
| microtubule-organizing center (MTOC) |
|
|
Term
| The (-) end of the MTOC is anchored near...and the (+) end is attached to... |
|
Definition
| The (-) end of the MTOC is anchored near the nucleus and the (+) end is attached to integral proteins in the plasma membrane |
|
|
Term
| Explain the structure of tubulin |
|
Definition
| Tubulin is a dimer of alpha-tubulin and beta-tubulin (tubulin monomers) |
|
|
Term
| True/False: Tubulin does not form spontaneously; it requires an enzyme. |
|
Definition
| FALSE...tubulin DOES form spontaneously and it does NOT require an enzyme |
|
|
Term
| Tubulin monomers are activated by |
|
Definition
| Tubulin monomers are activated by GTP |
|
|
Term
| Tubulin dimers join together to form... |
|
Definition
| Tubulin dimers join together to form a single-stranded protofilament |
|
|
Term
| Cells regulate microtubule growth and shrinkage via |
|
Definition
| Cells regulate microtubule growth and shrinkage via hormones and NTs |
|
|
Term
| Difference between GTP bound with alpha tubulin and GTP bound with beta tubulin? |
|
Definition
| GTP bound with alpha tubulin is inactive while GTP bound with beta tubulin can be hydrolyzed (for dimer formation) |
|
|
Term
| How many tubulin dimers can make a circular tube? |
|
Definition
| 13 dimers can make a circular tube |
|
|
Term
| A protein that binds to microtubules to alter its structural or functional properties |
|
Definition
Microtubule-Associated Proteins (MAPs) (ex: Taxol and colchicine...they disrupt the microtubule dynamis and affect cell division, therefore often used as anti-cancer medicines) |
|
|
Term
| Factors affecting growth/shrinkage of microtubules |
|
Definition
1.Local concentration of tubulin (more high [tubulin] promotes growth..at low concentrations MTs tend to shrink)
2.Dynamic instability (MT will grow for a few seconds then shrink for a few seconds)...if the GTP bound to the beta-tubilin is hydrolyzed, the MT will shrink
3.MAPs
4.chemicals that disrupt the dynamics |
|
|
Term
| Preventing microtubules from dissociating impairs many cellular processes, including... |
|
Definition
|
|
Term
| MAPs regulate....and are targets of... |
|
Definition
| MAPs regulate microtubule dynamics and are targets of hormone regulation |
|
|
Term
| Microtubules are connected to each other and to membrane proteins by... |
|
Definition
| microtubule-associated proteins (MAPs) |
|
|
Term
Direction of motor proteins is determined by...
..Kinesin and Dynein move in what directions? |
|
Definition
Direction of motor protein movement is determined bypolarity and type of motor protein.
Kinesin moves in the (+) direction (anterograde)..Dynein moves in the (-) direction (retrograde) |
|
|
Term
Movement of motor proteins is fueled by...
and the rate of movement is determined by... |
|
Definition
| Movement of motor proteins is fueled by the hydrolysis of ATP...the rate of movement is determined by the ATPase domain of the motor protein and regulatory proteins |
|
|
Term
| How does the rate of movement of dynein compare to kinesin? |
|
Definition
| Dynein is larger and moves 5 times faster than kinesin |
|
|
Term
| Describe how vesicles are carried from the cell body to the synapses in neurons |
|
Definition
| Vesicles filled with NT travel from the cell body to the synapse on kinesin in the anterograde direction...empty vesicles brought back from the synapse by endocytosis are carried back towards the cell body on dynein in the retrograde direction |
|
|
Term
| Describe the differences between microvilli and cilia |
|
Definition
| Microvilli are short, non-mobile, and made up of actin filament. Cilia are long, mobile, and made up of microtubules in a 9+2 formation |
|
|
Term
| Bundle of parallel microtubules (9 pairs of microtubules around a central pair) that make up the structure of cilia and flagella |
|
Definition
|
|
Term
| The waving of cilia and whipping of flagella result from... |
|
Definition
| the asymmetric activation of dynein on opposing sides of the axoneme |
|
|
Term
| If all dyneins on the microtubules of an axoneme were activated... |
|
Definition
| nothing would occur...asymmetric activation is necessary for movement |
|
|
Term
|
Definition
| Cytoplasmic and Axonemal dynein |
|
|
Term
| The nine microtubule doublets that make up part of an axoneme are connected by... |
|
Definition
|
|
Term
| How do microtubules function in the nervous system, hormones and cell signaling, and respiration and digestion? |
|
Definition
Nervous system: Microtubules support the structure of long axons.
Hormones and cell signaling: Microtubules carry hormone containing vesicles from the site of synthesis to release.
Respiration and digestion: Cilia (made up of microtubules) propel mucus and other fluids over the epithelial surface (cilia also found on sensory receptors) |
|
|
Term
| Microfilaments are polymers of... |
|
Definition
|
|
Term
| Microfilament movement arises from... |
|
Definition
| actin polymerization and sliding filaments using myosin (more common) |
|
|
Term
| Actin monomers aka ____, polymerized to form... |
|
Definition
| G-actin (actin monomers) polymerize to form a polymer called F-actin |
|
|
Term
| True/False: F-actin is formed by spontaneous growth, and grows 6-10 times faster at the + end |
|
Definition
|
|
Term
| Explain treadmilling of actin |
|
Definition
| Assembly and disassembly occurs simultaneously so that the overall length is constant |
|
|
Term
| What are capping proteins? |
|
Definition
| Proteins that bind to and stabilize the (-) end of microfilaments, preventing disassembly so that the microfilament can grow |
|
|
Term
| Two arrangements of microfilaments in the cell |
|
Definition
1.Tangled networks: Microfilaments linked together by long, flexible actin-binding proteins called filamin.
2.Bundles: Cross-linkage of microfilaments by short actin-binding fascin protein |
|
|
Term
Networks and bundles of microfilaments are attached to the cell membrane by...
this functions to... |
|
Definition
| dystrophin protein...this helps maintain cell shape and can be used for movement |
|
|
Term
| The 2 types of amoeboid movement |
|
Definition
| 1.Movement by filapodia and 2.Movement by lamellipodia |
|
|
Term
| What is filapodia and what is its function? |
|
Definition
| Filapodia are rodlike extensions of the cell membrane, supported by the actin cytoskeleton. It is used to make neuron connections and to build microvilli |
|
|
Term
| What is lamellapodia and what is its function? |
|
Definition
| Lamellapodia are sheetlike extensions of the cell membrane supported by the actin cytoskeleton. Permits movement of white blood cells (macrophage cells) |
|
|
Term
| All myosin isoforms have a similar structure which consists of (and their functions) |
|
Definition
| a Head (ATPase activity), Tail (can bind to subcellular components) and a Neck (regulates the ATPase) |
|
|
Term
| Hormones regulate myosin function via... |
|
Definition
| phosphorylation of light chains |
|
|
Term
| If the sliding filament model is analogous to pulling yourself along a rope, then what is the rope and what is your arm? |
|
Definition
| The rope is Actin and your arm is myosin...the myosin neck stretched and head is pushed forward and myosin forms a bond with actin...then myosin bends, pulling the actin towards the tail. |
|
|
Term
| The linkage of a myosin head to an actin subunit |
|
Definition
|
|
Term
| The part of a cross-bridge cycle in which structural changes in myosin alter the relative position of the actin filament |
|
Definition
|
|
Term
| The chemical reaction that takes place during the cross-bridge cycle is...and the structural change is... |
|
Definition
Chemical reaction= myosin binding to actin (cross bridge)
Structural change= myosin bends (power stroke) |
|
|
Term
| Describe the cross-bridge cycle |
|
Definition
| Formation of cross-bridge, power stroke, release, and extension |
|
|
Term
| How is the cross-bridge broken? |
|
Definition
| By the binding of ATP to the myosin |
|
|
Term
| ATP hydrolysis on myosin head after detaching from actin causes...and what happens upon release of the phosphate? |
|
Definition
| myosin to extend in the plus direction of the microfilament..upon release of the phosphate, myosin bends and power stroke occurs |
|
|
Term
| True/False: Actino-myosin activity depends on which of the two (actin or myosin) is free to move. |
|
Definition
| TRUE..if the actin microfilament is immobile, then myosin walks along the microfilament...if myosin is immobile (attached to the plasma membrane) the actin filament moves |
|
|
Term
| The distance myosin steps during each cross-bridge cycle |
|
Definition
|
|
Term
| What does unitary displacement depend on? |
|
Definition
| The myosin neck length and location of binding sites on actin (helical structure of actin) |
|
|
Term
| The proportion of time in each cross-bridge cycle that myosin is attached to actin...and how long is this? |
|
Definition
| Duty cycle..typically~0.5 (myosin is tightly bound to actin for half of each cross-bridge cycle) |
|
|
Term
| What is a typical solution to myosin moving along the actin filament and falling off? |
|
Definition
| Use of multiple myosin dimers (climbing using both arms and legs, instead of just one arm) |
|
|
Term
| Contractile cells unique to animals |
|
Definition
|
|
Term
| The 2 contractile elements within myocytes: |
|
Definition
| Thick filaments and thin filaments |
|
|
Term
| Thick filaments and thin filaments are made up of.. |
|
Definition
Thick filaments are polymers of myosin (~300 myosin II hexamers)
Thin filaments are polymers of alpha-actin |
|
|
Term
| How are thin filaments stabilized to prevent spontaneous growth or shrinkage? |
|
Definition
| Each thin filament is capped by tropomodulin at the minus end and CapZ at the plus end |
|
|
Term
| How do thin filaments regulate contraction> |
|
Definition
| Thin filaments have the proteins troponin and tropomyosin which mediate the interaction b/w actin and myosin |
|
|
Term
Thick muscle filaments consist mainly of...
and Thin muscle filaments consist mainly of... |
|
Definition
| Thick muscle filaments consist mainly of myosin molecules connected by the tail. Thin filaments consist mainly of actin. |
|
|
Term
| Two main types of muscle cells |
|
Definition
| 1.Striated (skeletal and cardiac...actin and myosin arranged in parallel) and 2.Smooth (actin and myosin not arranged in any particular way) |
|
|
Term
| The contractile unit of striated muscle |
|
Definition
|
|
Term
| Forms the border of each sarcomere...thin filaments are attached to this and extend from it towards the middle of the sarcomere |
|
Definition
|
|
Term
| Middle region of the sarcomere occupied by thick filaments |
|
Definition
| A band (anisotropic band) |
|
|
Term
| Located on either side of the Z-disk and occupied by thin filament |
|
Definition
|
|
Term
| In a sarcomere, each thick filament is surrounded by... |
|
Definition
|
|
Term
| The 3D organization of thin and thick filaments in a sarcomere is maintained by... |
|
Definition
| Nebulin (runs along the length of the thin filament) and Titin (connects the thick filament to the Z-disk) |
|
|
Term
|
Definition
From left to right on the top: I band, A band, I band From left to right on the bottom: CapZ, Z disk, Titin, thin filament, tropomodulin, thick filament, nebulin, Z disk |
|
|
Term
| True/False: Unlike in other cells, myosin II of muscle actino-myosin activity cannot drift from the actin |
|
Definition
|
|
Term
|
Definition
|
|
Term
| True/False: Unitary displacement of myosin II in muscle cells is very long |
|
Definition
| FALSE...unitary displacement of myosin II in muscle cells is SHORT...small amount of filament sliding with each movement of the myosin head |
|
|
Term
| A single continuous stretch of interconnected sarcomeres |
|
Definition
| myofibril (which extends the length of the muscle cell) |
|
|
Term
|
Definition
| Sarcolemma= the plasma membrane of a muscle cell |
|
|
Term
| The translation of an excitatory signal at the sarcolemma into a stimulation of contraction |
|
Definition
| Excitation-contraction coupling (EC coupling) |
|
|
Term
| EC coupling is a combination of physical and chemical changes w/in the myocyte that elevate... |
|
Definition
| Ca2+ concentration (causing contraction)...relaxation occurs when Ca2+ concentration in the cell decreases |
|
|
Term
| How does the increase of cytoplasmic Ca2+ cause contraction of muscle? |
|
Definition
| At rest, [Ca2+] is low, and Troponin-tropomyosin cover myosin binding sites on actin. As [Ca2+] increases, Ca2+ binds to TnC (troponin binding site), troponin-tropomyosin moves, and myosin-binding site on actin is exposed. Myosin binds to actin and the cross-bridge cycle occurs. |
|
|
Term
| Which isoform has a higher affinity for Ca2+, fTnC or s/cTnC? |
|
Definition
| fTnC has a higher affinity for Ca2+ (muscles with fTnC isoform repond to smaller increases in cytoplasmic Ca2+) |
|
|
Term
| Isoforms differ in the affect of |
|
Definition
|
|
Term
| Are the action potentials more prolonged in skeletal or cardiac muscle? |
|
Definition
| Action potentials are prolonged in cardiac muscle (attributed to Ca2+ channels being opened longer) |
|
|
Term
| How does the initial cause of depolarization of skeletal and cardiac muscles differ? |
|
Definition
| Cardiac muscle consists of Myogenic Muscle Cells (spontaneous contraction beginning in the muscle) and Skeletal muscle consists of Neurogenic Muscle Cells (contraction stimulated by the action of neurons..excited by NTs from motor nerves) |
|
|
Term
| True/False: Pacemaker cells have unstable resting membrane potential |
|
Definition
|
|
Term
| Acetyl CoA is synthesized in... |
|
Definition
|
|
Term
| What is converted by what enzyme to produce ACh |
|
Definition
| Acetyl CoA + Choline are converted to ACh by choline acetyltransferase (ChAT) |
|
|
Term
| Invaginations of sarcolemma that enhance penetration of action potentials into the myocyte |
|
Definition
| Transverse tubules or T-tubules |
|
|
Term
| The endoplasmic reticulum of muscle cells that stores Ca2+ bound to the protein squestrin |
|
Definition
| Sarcoplasmic Reticulum (SR) |
|
|
Term
| Cardiac and skeletal muscles accumulate Ca2+ within their SR to ensure... |
|
Definition
| that the cell maintains a low intracellular [Ca2+] |
|
|
Term
| In striated muscle, the SR frequently has enlargements, called Terminal Cisternae which functions to... |
|
Definition
| increase the capacity for Ca2+ storage and localize it to discrete regions within the muscle cell |
|
|
Term
| True/False: T-tubules and terminal cisternae are adjacent to one another |
|
Definition
|
|
Term
| Action potential propagates along the sacrolemma and down...which stimulates ..and triggers the release of... |
|
Definition
| During EC coupling, the action potential propagates along the sacrolemma and down the T-tubules, which stimulates DHPR and triggers the release of Ca2+ from the SR |
|
|
Term
| Following the action potential in EC coupling, Ca2+ is actively transported... |
|
Definition
|
|
Term
| Where are Ryanodine receptors? Where are Dihydropyridine receptors? What are these? |
|
Definition
| These are voltage-gated Ca2+ channels...Ryanodine receptors (RyR) are in the SR membrane. Dihydropyridine receptors (DHPR) are in the muscle plasma membrane |
|
|
Term
| Ca2+ transporters in the cell membrane and Ca2+ transporters in the SR membrane |
|
Definition
Cell Membrane: sodium-calcium exchanger (NaCaX), Ca2+ATPase, DHPR SR: RyR, Ca2+ATPase
|
|
|
Term
| Explain how in the heart, APs cause "Ca2+ induced Ca2+ release" and how in skeletal muscle, APs cause "depolarization induced Ca2+" release |
|
Definition
| Heart muscle: Once DHPR opens, Ca2+ enters the cell which causes cardiac muscle RyR to open and SR releases Ca2+. In skeletal muscles, the change in DHPR shape causes RyR to open and release Ca2+ from SR..even if there is no influx of Ca2+ |
|
|
Term
|
Definition
| Parvalbumin is a Ca2+ binding protein in the cytoplasm of some muscles which buffers Ca2+ levels to accelerate relaxation |
|
|
Term
|
Definition
cardiac vs. skeletal cell morph: single cells vs. multiple cells fused into large myofibers excitation: myogenic and involuntary vs. neurogenic and usually voluntary action potential: slow repolarization with long refractory period vs. fast repolarization with short refractory period ec coupling: Ca2+ induced Ca2+ release vs. depolarization induced Ca2+ release sr: well-developed terminal cisternae (in birds and mammals...poorly developed in lower vertebrates) vs. amount of terminal cisternae depends on fiber type
|
|
|
Term
| True/False: Smooth muscle contractions are fast and transient |
|
Definition
| FALSE...smooth muscle contractions are slow and prolonged |
|
|
Term
| Key differences between smooth and skeletal muscle (5) |
|
Definition
Smooth muscles:
1.Don't have sarcomeres (no striations)
2.Don't have T-tubules and have a minimal SR
3.Often connected by gap junctions (function as a single unit)
4.Contract in ALL dimensions
5.Difference mechanism of EC coupling |
|
|
Term
| In smooth muscle, thin filaments are fixed to the plasma membrane by |
|
Definition
|
|
Term
| Smooth muscle contractions are regulated by |
|
Definition
| nerves, hormones, and physical conditions |
|
|
Term
|
Definition
| Caldesmon is the protein that is bound to actin to block myosin binding in smooth muscles (smooth muscles do not have troponin) |
|
|
Term
| Stimulation of smooth muscle cell increases intracellular Ca2+ which binds to |
|
Definition
| Calmodulin...calmodulin binds caldesmon and removes it from actin so that cross-bridges can form and contraction can occur |
|
|
Term
| True/False: Calmodulin causes the phosphorylation of myosin which increases myosin ATPase activity. |
|
Definition
| TRUE: Calmodulin causes the phosphorylation of myosin which increases myosin ATPase activity |
|
|
