Myosin and actin filaments are kept in place by ?

Ans. is 'd' i.e., TitinThe side-by-side relationship between the myosin and actin filaments is difficult to maintain.This is achieved by a large number of filamentous molecules of a protein called titin.Titin molecules act as a framework that holds the myosin and actin filaments in place so that the contractile machinery of the sarcomere will work.Impoant muscle proteins Myosin :- Myosin is the protein that constitutes the thick filaments. Myosin of skeletal muscle is myosin-IL Myosin paicipates in the contractile mechanism and also acts as an ATPase.Actin :- Actin is the major protein of thin filament. It is the actin which slides over myosin during contraction.Tropomyosin : - It is the other protein of thin .filament. It covers the active sites (myosin binding sites) on actin. When Ca+2 concentration of cytoplasm (sarcoplasm) is raised, it uncovers the active sites of actin and allow the contraction So, the 'cross-bridge cycling' is switched off or on by the tropomyosin molecule which slides on the actin molecule to cover or uncover the active sites on it.