muscle cells are a part of muscles & muscle cells can store and release large amounts of energy ->  parts of muscles can store and release large amounts of energy  a bone is a part of a body & muscles push / pull bones to move the bones ->  muscles move parts of the body  moving changes stored energy into kinetic energy and heat energy & if a process changes something into something else, then that something is required for that process ->  an animal requires energy to move  muscles move parts of the body & an animal requires energy to move ->  muscles moving parts of the body requires energy  parts of muscles can store and release large amounts of energy & muscles moving parts of the body requires energy -> releasing energy is used by muscles to move parts of the body