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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
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)
isotonic contraction
what happens if increase weight (3)
-muscle contracts and shortens.

-lag appears
-velocity decreases
-height of lift decreased
structure of myofibril:
dark bands
light bands
boundary of sarcomere
thick filaments
thin filaments
-A bands
-I bands
-Z lines
-myosin
-actin
myosin structure (4)
-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)
actin structure (4)
-polymer
-naturally polymerizes
-coiled coil helical structure
-has regulatory proteins (tropomyosin, troponin) bound to it.
what portions of sarcomere shorten w/ contraction?
which remain the same?
-I, H (thick f.'s only), shortens
-A remains same
cross section of muscle:
organization of filaments
-hexagon of actin filaments around thick
-triangle of myosin around 1 actin
how many proteins are in 1 myosin?
how linked?
6: 2 motor domains (heads), 2 alpha helices, 2 light chains
-non covalently
myosin solubility (2)
-insoluble at physiological pH (end of the tail?)
-soluble at very high ionic strengths, aggregate at physiological pH
relation btw AP and muscle twitch
-twitch doesn't start until AP is finished
tetanus (3)
-constant contraction
-occurs when stimulus is above certain frequency
-happens when APs come fast enough
describe the isometric force of diff fiber lengths (static stretching, shortening of muscle)
-max force is produced at every point, but
-tetanus is only reached at optimal length
during what step of contraction is ATP hydrolized?
-release of actin, cocking of the myosin head (?)
what does the release of phosphate do to the actin/myosin complex
-increases actin affinity
-myosin can rotate = power stroke
what happens when ATP attaches to actin/myosin complex
-it attaches to myosin
-myosin's affinity for actin decreases :. myosin releases the actin.
what must be present on the myosin for actin to bind to it
-ADP and Pi