320Fall10Lecture10b - 1 BIO 320 Cell Biology, Fall 2010 Dr....

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BIO 320 Cell Biology, Fall 2010 Dr. Thomas Bushart Week 10 – part 2 1
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Platelets Utilizes caps, severing, cross-linking Spread out and then contract to pull closed damaged blood vessels 2
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3
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Myosin activation (non-muscle) Myosin light-chain kinase (MLCK) 4
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Muscle contractions Highly ordered arrays of actin filaments are moved against arrays of myosin II Muscle cells myofibrils sarcomeres Sarcomeres are the small contractile unit I Thin filaments – actin and associated proteins I Thick filaments – organized bipolar myosin II fibers 5
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Sarcomere shortening The ~300 myosin II heads walk towards plus ends I Lack of processivity and organization is good 6
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Filament stability Fibers need to be both stable and uniform I Capping proteins I Nebulin acts as a “molecular ruler” I Titin keeps myosin in center 7
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Ca 2+ leads to contraction 8
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Ca 2+ leads to contraction Tropomyosin stabilizes but can block binding of other proteins (myosin) Troponin I-T pulls tropomyosin over myosin- binding sites Troponin C binds Ca 2+ and causes troponin I to release tropomyosin 9
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Why do muscles lock into place after death? I
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320Fall10Lecture10b - 1 BIO 320 Cell Biology, Fall 2010 Dr....

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