SMT 2 again Flashcards
what happen when the calcium binds to troponin C in the muscle fiber cytosol?
the troponin complex undergoes a conformational change and Troponin T “pulls” tropomyosin and Troponin I off the myosin-binding site of G-actin subunits
what are the steps of cross-bridge cycle
- ATP hydrolysis
- cross-bridge formation
- power stroke
- detachment of myosin from actin
prior to myosin being able to bind to actin, it must be ?
“energized”
what happens when myosin is bound to ATP
it lowers it’s affinity for actin and there is no cross-bridge formation
what hydrolyses ATP -> ADP + Pi in the myosin head?
intrinsic ATPase activity
hydrolysis causes what change in the mysoin head?
causes the myosin head to pivot, moving down the actin filament so that it lines up with a new actin monomer
calcium binding to troponin, has uncovered what?
the mysoin-binding site on actin
the energized myosin head attached to the mysoin-binding site on actin and what is released?
Pi
when the myosin head is attached to the myosin-binding site, this creates what?
a myosin-actin cross bridge
the cross bridge generates force as what?
as myosin neck rotates toward center or sarcomere
what is getting closer together, shortening the sarcomere and generating force?
Z lines
what dissociates from myosin and the actin-myosin complex is left in a rigid, “attached” state?
ADP
what binds to myosin and myosin detaches from actin
ATP
what is isometric contractions?
muscle contracts against force transducer without decreasing muscle length
when does isometric contractions occur?
occurs when the load is greater than the force of muscle contraction
what is isotonic contractions?
muscle shortens against a fixed load
when does isotonic contractions occur?
occurs when the force fo the muscle contraction is greater than the load and the tension on the muscle remains constant
what binds to free calcium within the SR
calsequestrin and calreticulin
there are 2 main types of muscle fiber types which are?
type 1 (slow fibers)
type II (fast fibers)