40. In SMOOTH musele calcium bindsto initiate a contraction? A. troponin B. calm

Question

40. In SMOOTH musele calcium bindsto initiate a contraction? A. troponin B. calmodulin C. myosin D. SERCA pumps 41. The following is a list of the events that occur during a muscle contraction. 1. Myosin cross-bridges bind to the actin 2. The free myosin head splits ATP. 3. Caleium ion is released from the sarcoplasmic reticulum. 4. The myosin head pivots toward the center of the sarcomere 5. Calcium ion binds to troponin. 6. The myosin head binds an ATP molecule and detaches from the actin. The correct sequence of these events is A) 1, 3, 5, 4, 6, 2 B) 5, 1, 4, 6, 2, 3 C)3, 5, 1, 2, 4, 6 D) 3, 5, 1, 4,6, 2 E) 1, 4, 6,2, 3, 5. 42. Which of the following protein serves as an anchor to secure actin to the Z line? A. actin B. myosin C. tropomyosin D. titin 43. Skeletal muscle fibers differ from "typical cells" in that muscle fibers A. lack a plasma membrane. B. have many nuclei. C. are very small. D. lack mitochondria. 44. The principle that states the force of contraction is dependent on the degree of stretch or contraction prior to stimulation is the sliding filament theory uscle tone. length-tension relationship D. summation principle. 45. Fast muscle fibers are different than slow muscle fibers due to: A. decreased mitochondrial number. B. increased contractile power. C. lower myoglobin content. D. All of the above 46. Put the following structures in order from superficial to deep: 1. muscle fiber 2. perimysium 3. myofibril 4. fascicle 5. endomysium epimysiw

Explanation / Answer

40. B) Calmodulin

In smooth muscle contraction is initiated by calcium regulated phosphorylation of myosin. Here calcium bind to a molecule called calmodulin and form calcium calmodulin complex. This complex bind to myosin light chain kinase to activate it, which allows contraction to occur.

But, in cardiac and skeletal muscle, calcium bind to calcium binding protein troponin

SERCA(Sarcoendoplasmicreticulum calcium transport ATPase) pump is a pump that transport calcium ion from cytoplasm in to the sarcoendoplasmic reticulum.

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