Activity This assignment is due no later than 11:59 pm on Friday, Mar. 30, 2018.

Question

Activity This assignment is due no later than 11:59 pm on Friday, Mar. 30, 2018. When you are ready to submit your answer, select the assignment link shown above, select "Write Submission,"type your answer into the submission box, and select "Submit. Visit the website bttp://health.howstuffworks.com the olowinesm/muscle2.htm to read about actin, myosin, and muscle contraction. 1. What shape are actin molecules? 2. What shape are myosin molecules? 3. What are troponin and tropomyosin and why are they important? 4. How does calcium allow muscle contraction?

Explanation / Answer

1.Actin is the major cytoskeletal protein of most cells,which polymerize to form Actin filament -thin,flexible fibre approximately 7nm in diameter and upto several micrometer in length.it can be free as G-actin (monomer) and in linear polymer called as F-actin(microfilaments).

2.Myosin is a prototype of a molecular motor -a protein convert chemical energy in the form of ATP to mechanical energy,thus generating force and movement.Example-myosin2 present in muscle having two identical heavy chain and two pair of light chains.Each heavy chain consist of a globular head region and a long alpha -helical tail.it give the structure of a rod with 2 globular head in which heavy chain twist around each other in a coiled-coil structure to form a dimer.

3.Troponin and tropomyosin are regulatory protein in the muscle contraction.Troponin binds with the calcium ion which is necessary for muscle contraction as calcium bind with troponin ,it causes a conformational change which is transmitted to tropomyosin molecule,causing it to move towards the helical groove of thin filament ,out of blocking position.

4.The contraction of skeletal muscle is triggered by nerve impulses,that stimulate the release of calcium from sarcoplasmic reticulum.The increased calcium concentration signals muscle contraction via the action of two Actin binding protein troponin and tropomyosin.At high concentration,calcium bind to troponinC shifting the position of complex ,allowing access of myosin head to Actin and allow contraction to proceed.

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