Skeletal muscle cell, coloured transmission electron micrograph (TEM). The nucleus (bottom right) is displaced to the edge of the cell by the abundant supply of bundles of contractile myofilaments (purple). Myofilaments are proteins consisting of myosin and actin. When the cell is stimulated to contract, the myofilaments interact and slide past each other, resulting in a shortening of the cell. An abundance of mitochondria (dark purple), which produce the large amount of energy needed by the cell, can also be seen.
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