Please answer all three questions. Please make sure your answers are correct! Th
ID: 210734 • Letter: P
Question
Please answer all three questions. Please make sure your answers are correct! Thanks! All information needed to answer the question is with in the text. 24) In striated muscle, phosphate is released from the myosin head and a. the myosin head binds to actin. b. the myosin head releases from actin. c. the myosin head returns to the cocked position. d. the myosin head starts the power stroke 25) For contraction to occur in smooth muscle a. myosin light chains must be phosphorylated. b. myosin light-chain kinase must be phosphorylated. c. calcium must bind to troponin C d. DHPR must interact physically with ryanodine receptor calcium channels. 26) In the rigor formation myosin heads are... a. bound to actin with ADP and phosphate bound. b. bound to actin with ATP bound. c. bound to actin without ADP or ATP bound d. dissociated from actin with ATP bound. e. dissociated from actin with ADP and phosphate bound.Explanation / Answer
24. d) For muscle contraction ATP is required. When ATP binds to myosin head, the cross bridge between actin and myosin is broken. ATP is broken into ADP and inorganic phosphate by ATPase activity of myosin head and energy is released. This energy takes myosin to a higher energy level and the myosin head acquires a cocked position. It pulls actin inwards in a power stroke and in the process ADP and iP(inorganic phosphate) is released.
25. b) Myosin light chain kinase is a protein that phosphorylates myosin light chain. Phosphorylation causes a conformational change in the myosin head and initiates the cross-bridge cycling i.e. serial attachment and detachment of actin and myosin.
26. c) After the formation of actin-myosin bond, the two filaments can not detach until ATP attaches to myosin head. But after death, body can not produce ATP. So actin and myosin remain in bounded state. During power-stroke ADP and phosphate is released forming a stronger acto-myosin bond.