Answer
Myofibrils are long protein cords ( 1 U dia) that occupy most of the cytoplasm of a muscle cell(myocyte/myofiber).
Myofilaments are long protein microfilaments of myofibrils. The myofilaments are of two kinds : the thick myosin filaments, and the thin filaments made of actin.
Work Step by Step
Thick filaments are about 15 nm thick. Each consists of several hundred molecules of the protein myosin in the form of two intertwined chains.The appearance is that of a bundle of gulf clubs , with the heads sticking out in helical array around the bundle.
Thin filaments are about 7 nm thick . The molecule presents as two intertwined strands of fibrous actin (F actin) . Each F actin molecule looks like a beaded necklace with a string of globular actin subunits
