<prompt> Type I muscle fibers rich in myosin heavy chain areFast contracting, susceptible to fatigueSlow contracting, susceptible to fatigueFast contracting, resistant to fatigueSlow contracting, resistant to fatigue  <response>: Ans. d Slow contracting, resistant to fatigueTwo Major Fiber Types: type I and type II fibers Type IType II Slow TwitchFast TwitchMyosin ATPaseLowHighEnergy utilizationLowHighMitochondriaManyFewColorRedWhiteMyoglobinYesNoContraction rateSlowFastDurationProlongedShortResistance to fatigueincreased morelessEducational points:ProteinLocationComment orjunctionTitinReaches from the Z line to the M lineLargest protein in body. Role in relaxation of muscle.NebulinFrom Z line along length of actin filamentsMay regulate assembly and length of actin filaments.ctr Act in inAnchors actin to Z linesStabilizes actin filaments.DesminLies alongside actin filamentsAttaches to plasma membrane plasmalemma.DystrophinAttached to plasmalemmaDeficient in Duchenne muscular dystrophy.Mutations of its gene can also cause dilated cardiomyopathy.CalcineurinCytosolA calmodulin-regulated protein phosphatase.May play important roles in cardiac hypertrophy and in regulating amounts of slow and fast twitch muscles.Myosin-binding protein CArranged transversely in sarcomere A-bandsBinds myosin and titin. Plays a role in maintaining the structural integrity of the sarcomere. 