vitamin K science definition

Any of a group of fat-soluble vitamins that are involved in the formation of prothrombin and other clotting factors in the liver and are essential for normal clotting of the blood. (The K is derived from the German word koagulation.) Vitamin K is also involved in bone formation and repair. Two forms occur naturally: vitamin K₁, which is synthesized by plants, and vitamin K₂, which is mainly synthesized by intestinal bacteria. The other forms are synthetic substances with similar chemical structures.

The major dietary form of vitamin K that is synthesized in plants and found primarily in green, leafy vegetables such as alfalfa and in vegetable oils. It can be made synthetically and is given orally to treat prothrombin deficiency that results from heparin and other anticoagulant drugs. Also called phylloquinone. Chemical formula: C₃₁H₄₆O₂.

A form of vitamin K that is synthesized by bacteria in the intestine and is also found in fish and other foods. Also called menaquinone. Chemical formula: C₄₁H₅₆O₂.