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34 Cards in this Set
- Front
- Back
What is the structure of an Axoneme
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a cylinder of microtubules, 9 doublet microtubules (A - complete microtubule with 13 protofilaments and B an incomplete microtubule with 9 protofilaments that shares 3 from A), all around a central pair of 2 microtubules
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What is a Basal Body and what does it do?
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a microtubule organizing center that nucleates the - end of the axoneme
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What is axonemal dynein?
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it's covalently attached to the A microtubule and walks along the neighboring microtubule towards the - end
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What causes the specific movements in cilia and flagella?
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patterned activation/inhibition of dynein
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what is Nexin?
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Like a spring between adjacent doublet microtubules that holds them together, but still allows movement
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what is a Radial Spoke?
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holds outside doublet microtubules in register to the central doublet
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Name 4 differences between cilia and flagella
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number per cell, length, pattern of beating, direction of movement
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cilia vs flagella: number per cell
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many cilia per cell (if it has cilia). Usually 1, sometimes 2 flagella per cell
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cilia vs flagella: length
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cilia are short (1-2 micro m). flagella are long (100 micro m)
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cilia vs flagella: pattern of beating
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cilia - like an oar or backstroke
flagella - undulating, corkscrew pattern |
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cilia vs flagella: direction of movement
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cilia - perpendicular to direction of movement
flagella - parallel to direction of movement |
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What are myosins in general?
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molecular motor proteins that walk along the actin cytoskeleton
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What is myosin II specifically?
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walks towards the + end of an actin filament
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What is the structure of muscle? (general)
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muscles are bundles of muscle fibers. muscle fibers (or cells), are bundles of myofibrils. Myofibrils are made up of many sarcomeres.
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Describe a sarcomere (general)
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Defined as from Z line to Z line. Actin filaments perpendicular and stabilized at + end on Z line. Heavy chains (myosin II) in between actin filaments.
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What is the Z line?
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stabilizes and locks the + ends of actin filaments. defines boundaries of sarcomeres
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What is the A band?
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the length of heavy chain (myosin II)
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What is the I band?
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the region around the Z line that is devoid of heavy chain
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What is the H zone?
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the region of heavy chain only
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A cross section of a muscle would show what?
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A heavy chain surrounded by 6 light chains
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What is an oligomer?
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A protein that exists as multiple subunits associated
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How does myosin II exist?
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as an oligomer. the heads have an orientation
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What is the structure of myosin II protein?
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A head that binds to actin and hydrolyzes ATP. A neck like a spring. Tails that mediate oligomerization.
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What are the four steps of muscle contraction?
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1. Myosin w/ADP associates with actin
2. When myosin binds w/actin, it does a "power stroke" and releases ADP 3. ATP binds the myosin and it is released from actin 4. The ATP on the myosin is hydrolyzed "cocking the spring" of myosin |
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Muscle contraction is an example of converting _____ energy into ______ energy
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chemical, potential
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What is the structure of troponin?
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3 domains:
i - inhibitory domain c - binds to Ca2+ t - binds to tropomyosin |
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What is the structure of tropomyosin?
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long protein draped along actin filament, blocking actin/myosin interactions
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How do troponin and tropomyosin interact to regulate muscle contraction?
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In the presence of elevated Ca2+, troponin binds Ca2+, which changes the conformation of tropomyosin, removing it from the inhibitory site. This allows myosin to bind to actin -> muscle contraction!
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nerve to muscle: 1. action potential
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depolarization down the axon. Na+ in, K+ out
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nerve to muscle: 2. presynaptic terminus
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voltage gated channels open, calcium floods in, vesicles at presynaptic terminus fuse to membrane and release acetylcholine
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nerve to muscle: 3. synaptic cleft
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acetylcholine binds acetylcholine receptors on the muscle, which are part of ligand gated ion channels (the ligand being acetylcholine). the channels open and let in lots of Na+
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nerve to muscle: 4. muscle cell
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when Na+ floods the cell, voltage gated Ca2+ channels open, and Ca2+ floods the cell, binds troponin, changes conformation, moves tropomyosin, allows myosin to bind actin, muscles contract w/help of ATP
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How do acetylcholine vesicles get to presynaptic terminus?
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transported from neuron cell body down the axon by kinesin on microtubules
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How do you build muscle?
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add more myosin monomers to myosin thick filament. Can only add more myosin by adding more sarcomeres.
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