Contractile Tissue and Muscle Proteins - By Bhoomika Sharma
About Me I am pursuing for Bachelors in Biology. Acting Enthusiast. Always up for books, food and travel I write a blog on Fashion and Beauty My inspiration comes from everything peaceful. Bullet Journal addict.
Muscular contraction Muscular tissue is responsible for the movement of the body and for the movement of its various parts with respect to one another. It carries out mechanical work by contracting which involves a shortening and thickning of Its fibres. It is mad up of cells or fibres elongated in the direction of contraction. The contracting elements are the minute thread like myofilaments within the fibre. The protoplasm of muscle cells is given a special name sacroplasm. Muscles are classified on both functional and a structural basis. Functionally they are either voluntary or involuntary
Types There are 3 main types of muscle tissue: .Skeletal Muscle (also called Striated Muscle) Smooth Muscle, and Cardiac Muscle (located only in the heart)
Types of Muscle Cardiac muscle Skeletal muscle Smooth muscle
A typical skeletal muscle consists of two types of tissues: ntractile tissue and Supporting tissue. . Contractile tissue: The contractile tissue of each muscle is composed of numerous muscle fibres. Each muscle fibre is a multinucleated cross-striated cylindrical cell. The length of each muscle fibre is between 1 and 300 mm. It consists of a cell membrane (sarcolemma), which encloses the cytoplasm (sarcoplasm). There are two types of substances embedded in the sarcoplasm . T S veral nuclei arranged at the periphery beneath the arcolemma. A number of evenly distributed longitudinal threads callea myofibrils.
. Each myofibril shows alternate light and dark bands. Dark bands are Anisotropic and thus are known as A-bands. The light bands are Isotropic and thus are known as I-bands. The bands of adjacent fibrils are aligned transversely so that the muscle fiber appears cross striated. In the middles of the A band (dark band) there is a light H band. In the middle of the H band there is a dark M line. In the middle of the I band (light band) there is a dark Z disk also known as Krause's membrane. The segment of myofibril between twoz discs is called sarcomere.
The energy required for muscle contraction is provided by the oxidation of carbohydrates or lipids. The term mechanochemical reaction has been used for this conversion of chemical into mechanical energy. .The molecular process underlying the reaction is known to involve the fibrous muscle proteins, the peptide chains of which undergo a change in conformation during contraction.
Sarcomere Banding Pattern Z disc H zone Z disc Thin (actin) filament Thick (myosin) filament- I band A band I band M line i_.._ sarcomere M line Z disc Z disc Thin (actin) filament Elastic (titin) filaments Thick (myosin) filament
-band A-band I-band Z-line H-zone Z-line Myosin filament Actin filament
Heavy meromyosin catalyze the hydrolysis of ATP. It binds to actin.but does not form filament.HMM consists of a rod attached to a double headed globular region.it can be split further into two globular sub fragments (called HMM S -1) and one rod shaped sub fr gments (called HMM S-2). Each HMM S 1 fragment contains an ATPase active site and a binding site for a actin.furthermore the light chains of myosin are bound to the HMM S-1fragments. Probably, the light chains modulate the ATPase activities of myosin.
Actin filamen Troponin (TN) Tropomyosin (TM)
Tropomyosin Tropomyosin is a double stranded a-helical rod which is located in the groove between the two helical strands of actin. A troponin complex is attached to the tropomyosin at intervals of about 385 angstrom
Tropomyosin -chain -chain
Troponin . Troponin is a complex of 3 polypeptide chains designated TpC (calcium binding subunit) , Tpl (inhibitory subunit) and TpT (tropomyosin binding subunit). Troponin is an important c ntrol protein , that n as much as it prevents the teraction between actin and myosin unless combined with calcium ions. tpC binds with calcium ion and turns on contraction whereas Tpl binds to actin turning off 4-7 actin monomers. tpT binds to tropomyosin and restores calciunm ion sensitivity, this regulating the actin activity, depending on the calcium ion level.
deet. Cat+ Tropomyosin Troponin ctin Myosin