Describe how the thin actin filament and the myosin head of a thick filament interact during one contraction cycle by arranging the steps below in the correct order. In this case, assume the following: * ATP has just bound to a myosin head, causing the myosin head to dissociate from the thin filament in a sarcomere. * Ca2+ is bound to the regulatory protein troponin on the thin filaments so that troponin has changed shape and pulled the tropomyosin filament away from the myosin binding sites on actin. For this question, you will use each answer once and only once. Step 1: [Choose] The phosphate group dissociates (is "ejected") from the myosin head. The ATP molecule bound to the myosin head is hydrolyzed (broken down) into a phosphate group and an ADP molecule. The myosin head changes shape -- and the affinity of the myosin head for the attached phosphate group decreases. The myosin head changes shape -- from the bent "flexed" position to the the elongated "cocked" position. ADP dissociates (is "ejected") from the myosin head so that the myosin head is free to again bind ATP. The "power stroke" pulls the thin filament closer to the M-line and the sarcomere shortens. The "power stroke" begins as the myosin head changes shape -- from the elongated "cocked" position to the bent "flexed" position. Step 2: [Choose] Step 3: [Choose] Step 4: [Choose] Step 5: [Choose] Step 6: [Choose] Step 7: [Choose]
Added by Paula N.
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Step 1: ATP hydrolysis occurs, causing the myosin head to change shape and become energized. Show more…
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Arrange the steps of muscle contraction in the correct order Myosin head forms cross bridge with actin microfilament (thin filament) ATP binds to myosin - myosin detaches from actin filament ATP hydrolysis causes conformation change of myosin to the high-energy "cocked" configuration Phosphate is relased from myosin head Myosin undergoes a conformational change; sliding the thin filament (Power Stroke) ADP is released from myosin head
Sri K.
The myosin head is bound to ATP, ADP, and Pi when it is in the low energy conformation, and it is bound to the thin filament. No nucleotide. The myosin head is bound to ADP and Pi when it is in the extended, high energy conformation. ATP, ADP, and Pi. The myosin head is bound to ADP and Pi during the power stroke. Cross-bridge formation occurs when the myosin head is bound to no nucleotide. ADP and Pi. The absence of ATP would prevent the myosin head from detaching from the thin filament. The myosin head is bound to ATP when it is in the low energy conformation and is not bound to the thin filament.
Adi S.
Match the following terms for how myosin moves along actin with their corresponding definition/: - Attached - Released - Cocked - Force-generating A. The cleft closes like a clam shell around the ATP molecule B. ATP binding reducing the affinity for the head to the actin filament C. Pre-ATP binding, the myosin head is attached to the actin filament D. Weak binding of the head to the filament leads to release of phosphate
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