A small toy airplane is flying in the ?xy?-plane parallel to the ground. In the time interval ?t = 0 to ?t? = 1.00 s, its velocity as a function of time is given by = (1.20 m/s2)?tî? + [ 12.0 m/s ? (2.00 m/s2)?t?]?j?. At what value of ?t? is the velocity of the plane perpendicular to its acceleration?
Actin and Myosin II – Muscle Power Myosin II o Short lever arm with 2 light chains Myosin V o Long lever arm with 6 light chains Myosin’s power stroke – head takes 1 step o Use the energy of ATP to crank up the lever arm Bind to actin filament Release and take a step o Every step uses the energy of 1 ATP o The head domain is firmly bound to actin o The lever arm swings from its high-energy state to its low energy state o Myosin movement is produced by a swivel motion of the lever arm o Speed of movement depends on the speed of the cycle and how long of a step it can take Conformational changes in the myosin head drives the power stroke o Myosin head attached to actin filament No ATP or ADP – it is strongly attached to the filament o ATP concentration in the cell is high When the pocket is empty ATP almost instantaneously binds ATP causes the dissociation of the head from the actin filament o Hydrolyze ATP when you are away from the actin filament Use the energy of ATP hydrolysis to crank the lever arm into a high-energy state Head contains ADP + phosphate o Regain a little affinity to bind again to the actin filament Release phosphate from the head causing the power stroke o Back in a high affinity state – very firmly bound to the actin filament Have ADP in
