15 - Post-Mortem Changes in Meat

15 - Post-Mortem Changes in Meat - Post-Mortem Changes in...

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Post-Mortem Changes in Meat April 5-7, 2010 - A muscle is composed of bundles of 20-40 muscle fibres. - Fibres are multi-nucleated - A single muscle fibre is made up of bundles of ~2000 myofibrils individually enclosed by a membrane, the sacrolemma. - Myofibrils are composed of an orderly array of sacromeres, containing thick and thin filaments. - When you have the cross-linking, you have different 4° structure of protein can turn to actinmyosin or actomyosin - Ca2+ from SR and ATP supply are important for muscle contractions Skeletal Muscle Fibers Definitions: Sarcolemma – cell membrane Sarcoplasm – muscle cell cytoplasm Sarcoplasmic reticulum – stores calcium until it is released for muscle contraction (modified ER) Sarcomeres – regular arrangement of myofibrils (distance between two Z lines) Myofibrils are made of thick filaments (myosin) and thin filaments (actin) I band: the length of actin, but doesn’t include any of the zone of overlap; changes length during contraction because the length of overlap changes as contraction (I band decreases as zone of overlap increases during contraction) A band : the length of myosin; length stays the same H zone : myosin length but not including zone of overlap; length gets shorter as overlap increases with contraction Z line : define boundary of sacromere; gets shorter as filaments slide over one another during contraction *I band, H zone, sacromere get shorter with muscle contraction* *A band stays the same with muscle contraction* Thin filaments made of: F-actin : composed of two strands of G-actin molecules Tropomyosin : covers active sites on G-actin when the muscle is relaxed Troponin : calcium-binding protein Thick filaments made of: Bundles of myosin proteins around titan core o Myosin molecules have a globular head and an elongated tail o Heads form cross-bridges during contraction by binding to active sites on actin The shortening of muscle during contraction is due to the sliding of thick and thin filaments over another. To have shortening of a muscle:
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15 - Post-Mortem Changes in Meat - Post-Mortem Changes in...

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