Lecture 18 11

Lecture 18 11 - Lecture 18 11/26/07 Cytoskeleton Myosin...

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Lecture 18 11/26/07 Cytoskeleton – Myosin continued and Microtubules Myosin is a motor protein used by muscle cell for contraction/formation Muscle cell structure – long cylindrical cells, have multiple nuclei within each cell Myofibrils – Muscle cells made up of… Sarcomeres – unit of contractile activity within a muscle cell o Thin filaments – bands of F actin o Thick filaments – bands of actin and myosin o Z bands – ends of sarcomere o I band – only actin (thin filament) o A band – thin and thick filaments, makes up the darker region of muscle cell striation o H band – only thick filaments Sliding filament model of muscle contraction Movement of actin over myosin Sarcomere shortens in muscle contraction. When Sarcomere shortens, Z bands get closer together by maintaining distance of A band but shortening distance of I band and H zone Thin filament slide along thick filaments by myosin molecule binding and unbinding to the thin filament Muscle Contraction also require other proteins (in Sarcomere) Troponin – binds actin and tropomyosin Tropomyosin – longer protein that binds over top of 7 actin monomers Tropomyosin binds troponin on myosin binding site, it blocks myosin from being able to bind to actin when in relaxed state Contraction occurs when there is a flood of calcium, it binds to Troponin, cause release from Tropomyosin myosin binds to actin contraction Titan – large elastic protein, goes along entire length of Sarcomere, act as elastic bungee cord to cushion Sarcomere as it goes back and forth between relaxing and contracting
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Microtubules – hollow cylindrical tubular structure responsible for other cytoskeleton functions 1. Mechanical support 2. Controls cell shape 3. Controls organelle location Ex. Exocytosis and endocytosis: vesicles don’t just move randomly through cell, they actually move through cell along microtubule arrays. Motor proteins that move along microtubule able to bind to different vesicles are able to be endocytosed or exocytosed and move them to final location along microtubule network in cell. Microtubules are found in all eukaryotic cells.
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This note was uploaded on 07/21/2008 for the course BICD 110 taught by Professor Mel during the Fall '06 term at UCSD.

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Lecture 18 11 - Lecture 18 11/26/07 Cytoskeleton Myosin...

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