Kinesin and dynein use atp hydrolysis to carry things

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Kinesin and dynein use atp hydrolysis to carry things Heads walk along the tracks, tails carry things Microtubules are arranged in a way that have a positive and negative end – tells proteins which way to move
Motors , sarcomeres, filaments, myofibrils, myocytes and muscles Actin microfilaments are important part of cytoskeleton in most cells Myosin are motor proteins that walk along actin filaments Mysosin are in every cell, but muscle uses isoform myosin II Motors, sarcomeres, filaments, myofibrils, myocytes and muscles In a myocyte, the actin filaments are called thin filaments, arranged into an array Myosin are arranged into bundles thick filaments Z-disk allows filaments to orientate themselves in a known space apart Space is filled by myosin Troponin-troponin are actin binding proteins Thin filaments are decorated with actin-binding proteins: o troponin 3 sub-units, binds onto tropomyosin o Tropomyosin Job is to be a trigger Occur at regular intervals and control actin-myosin interactions Motors, filaments, sarcomeres, myofibrils , myocytes and muscles Thick and thin filaments are found in every muscle cell Smooth muscle has thick and thin filaments, but are scattered throughout the cell in all directions o contract in all directions to do its job striated muscle – repeating units (sarcomeres) o arranged in regular fashion sarcomeres are arranged end-end into long myofibrils myofibrils are the working bits Motors, filaments, sarcomeres, myofibrils, myocytes and muscles arrangement below means when activated, sarcomeres get smaller, as thick filaments pull thin filaments towards the middle
Although it’s called contraction, it means activation Motors, filaments, sarcomeres, myofibrils, myocytes and muscles Myofibrils are arranged side-by-side within a single cell (myocyte) Myocytes are arranged side-by-side to create a muscle Muscle also has non-myocytes that play important roles in structure (connective tissue) and function (immune cells, vasculature) True/false Actin is bigger than troponin – bad question o G-actin is bigger than troponin – ?? o F-actin is bigger than troponin – true Smooth muscles have thick and thin filaments but not sarcomeres Myofibers have multiple myofibrils Myocytes are one of many cell types in a muscle Skeletal muscle has both striated and smooth myocytes Z-disks do not change in size during contraction Thick filaments do not change in length when a sarcomere shortens Myosin is found only in muscle Myosin II is found only in muscle From myosin to contraction
Skeletal muscle is induced to contract by motor neuron releasing its neurotransmitter (acetylcholine, Ach) Ach binds its receptor (a Na+ channel) which initiates an action potential Action potential on cell surface triggers release of Ca2+ from intracellular stores High Ca2+ causes troponin/tropomyosin to move out of the way, permitting myosin to bind actin – actomyosins ATPase and force development Variation in muscle structure and function

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