The Collaborative International Dictionary
vitamin K \vitamin K\ n. (1929) [from G. Koagulationsvitamin.] either of two fat-soluble vitamins (vitamin K1 or vitamin K2) that help clot blood by participating in the fromation of prothrombin.
Syn: naphthoquinone.
Wiktionary
n. 1 Either of several related fat-soluble vitamins, found in leafy green vegetables, essential for blood clotting. 2 (context slang English) The drug ketamine.
WordNet
n. a fat-soluble vitamin that helps in the clotting of blood [syn: naphthoquinone, antihemorrhagic factor]
Wikipedia
Vitamin K is a group of structurally similar, fat-soluble vitamins the human body requires for complete synthesis of certain proteins that are prerequisites for blood coagulation that the body needs for controlling binding of calcium in bones and other tissues. The vitamin K-related modification of the proteins allows them to bind calcium ions, which they cannot do otherwise. Without vitamin K, blood coagulation is seriously impaired, and uncontrolled bleeding occurs. Low levels of vitamin K also weaken bones and promote calcification of arteries and other soft tissues.
Chemically, the vitamin K family comprises 2- methyl- 1,4-naphthoquinone (3-) derivatives. Vitamin K includes two natural vitamers: vitamin K and vitamin K. Vitamin K, in turn, consists of a number of related chemical subtypes, with differing lengths of carbon side chains made of isoprenoid groups of atoms.
Vitamin K, also known as phylloquinone, phytomenadione, or phytonadione, is synthesized by plants, and is found in highest amounts in green leafy vegetables because it is directly involved in photosynthesis. It may be thought of as the "plant" form of vitamin K. It is active as a vitamin in animals and performs the classic functions of vitamin K, including its activity in the production of blood-clotting proteins. Animals may also convert it to vitamin K.
Bacteria in the gut flora can also convert K into vitamin K. In addition, bacteria typically lengthen the isoprenoid side chain of vitamin K to produce a range of vitamin K forms, most notably the MK-7 to MK-11 homologues of vitamin K. All forms of K other than MK-4 can only be produced by bacteria, which use these forms in anaerobic respiration. The MK-7 and other bacterially derived forms of vitamin K exhibit vitamin K activity in animals, but MK-7's extra utility over MK-4, if any, is unclear and is a matter of investigation.
Three synthetic types of vitamin K are known: vitamins K, K, and K. Although the natural K and all K homologues and synthetic K and K have proven nontoxic, the synthetic form K ( menadione) has shown toxicity.
Usage examples of "vitamin k".
It also contains vitamin C, vitamin D, vitamin E, vitamin F, vitamin G, vitamin I, vitamin J, vitamin K, vitamin L, vitamin M, vitamin N, vitamin O, vitamin P, vitamin Q, vitamin R, vitamin T, vitamin U, vitamin V, vitamin W, vitamin X, vitamin Y, and, believe it or not, vitamin Z!