A molecular model of vitamin K2 (menatetrenone), a form of vitamin K that can be stored in animal tissue, playing a role in blood coagulation and maintaining bone mineral density. Vitamin K2 can be obtained through a diet consisting of fermented or aged cheeses and vegetables, eggs, beef, chicken, and dairy products, and can also be synthesized from vitamin K1. Atoms are colored dark gray (carbon), light gray (hydrogen), and red (oxygen).