Epidemiology
BII phobia is one of the more common types of phobia — it is estimated to affect about 3-4% of the general population.Onset of the phobia generally occurs in middle childhood, before the age of ten. There are more reports of incidence of the phobia in younger individuals and those with low education levels. Some studies suggest that women also experience the phobia more frequently, however results are mixed concerning relative prevalences of the phobia between the sexes. == References ==
Chemistry
Vitamin K is a fat-soluble vitamin that is stable in air and moisture but decomposes in sunlight. It is a polycyclic aromatic ketone, based on 2-methyl-1,4-naphthoquinone, with a 3-phytyl substituent. It is found naturally in a wide variety of green plants, particularly in leaves, since it functions as an electron acceptor during photosynthesis, forming part of the electron transport chain of photosystem I. Biological function
The best-known function of vitamin K in animals is as a cofactor in the formation of coagulation factors II (prothrombin), VII, IX, and X by the liver. It is also required for the formation of anticoagulant factors protein C and S. It is commonly used to treat warfarin toxicity, and as an antidote for coumatetralyl. Vitamin K is required for bone protein formation. Biosynthesis
Vitamin K1 is synthesized from chorismate, a compound produced from shikimate via the shikimate pathway. The conversion of chorismate to vitamin K1 comprises a series of nine steps:
Chorismate is isomerized to isochorismate by isochorismate synthase, or MenF (menaquinone enzyme). Addition of 2-oxoglutarate to isochorismate by PHYLLO, a multifunctional protein comprising three different enzymatic activities         (MenD, H, and C). Elimination of pyruvate by PHYLLO. Aromatization to yield o-succinyl benzoate by PHYLLO. O-succinylbenzoate activation to corresponding CoA ester by MenE. Naphthoate ring formation by naphthoate synthase (MenB/NS). Thiolytic release of CoA by a thioesterase (MenH). Attachment of phytol chain to the naphthoate ring (MenA/ABC4). Methylation of the precursor at position 3 (MenG).