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17 Cards in this Set
- Front
- Back
myosins:
what how many function |
-motor proteins
-20 families -actin based movement, bothe macroscopic and intracellular |
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isometric contraction
what happens when: muscle is lengthened shortened |
-muscle contraction with no change in length
-amount of force muscle can generate diminishes to 0 -same as lengthing (but more quickly) |
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isotonic contraction
what happens if increase weight (3) |
-muscle contracts and shortens.
-lag appears -velocity decreases -height of lift decreased |
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structure of myofibril:
dark bands light bands boundary of sarcomere thick filaments thin filaments |
-A bands
-I bands -Z lines -myosin -actin |
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myosin structure (4)
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-100nm coiled coil of 2 alpha helices
-2 globular "heads" (aka "motor domains") -2 slightly diff structured light chains -enzymatic region w/ actin binding site and ATP site -naturally aggregates w/ bipolar symmetry (heads facing opposite directions) |
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actin structure (4)
|
-polymer
-naturally polymerizes -coiled coil helical structure -has regulatory proteins (tropomyosin, troponin) bound to it. |
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what portions of sarcomere shorten w/ contraction?
which remain the same? |
-I, H (thick f.'s only), shortens
-A remains same |
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cross section of muscle:
organization of filaments |
-hexagon of actin filaments around thick
-triangle of myosin around 1 actin |
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how many proteins are in 1 myosin?
how linked? |
6: 2 motor domains (heads), 2 alpha helices, 2 light chains
-non covalently |
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myosin solubility (2)
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-insoluble at physiological pH (end of the tail?)
-soluble at very high ionic strengths, aggregate at physiological pH |
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relation btw AP and muscle twitch
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-twitch doesn't start until AP is finished
|
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tetanus (3)
|
-constant contraction
-occurs when stimulus is above certain frequency -happens when APs come fast enough |
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describe the isometric force of diff fiber lengths (static stretching, shortening of muscle)
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-max force is produced at every point, but
-tetanus is only reached at optimal length |
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during what step of contraction is ATP hydrolized?
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-release of actin, cocking of the myosin head (?)
|
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what does the release of phosphate do to the actin/myosin complex
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-increases actin affinity
-myosin can rotate = power stroke |
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what happens when ATP attaches to actin/myosin complex
|
-it attaches to myosin
-myosin's affinity for actin decreases :. myosin releases the actin. |
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what must be present on the myosin for actin to bind to it
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-ADP and Pi
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