Medicine & USMLE

Vitamin K Biochemistry

  1. Vitamin B1 (Thiamine) Biochemistry
  2. Vitamin B1 (Thiamine) Deficiency
  3. Vitamin B2 (Riboflavin)
  4. Vitamin B3 (Niacin) Biochemistry
  5. Vitamin B3 (Niacin) Deficiency and Excess
  6. Hartnup Disease
  7. Vitamin B5 (Pantothenic Acid)
  8. Vitamin B6 (Pyridoxine)
  9. Vitamin B7 (Biotin)
  10. Vitamin B9 (Folate)
  11. Vitamin B12 (Cobalamin) Biochemistry
  12. Vitamins B9 and B12 Deficiencies
  13. Vitamin A (Retinol) Biochemistry
  14. Vitamin A (Retinol) Deficiency and Excess
  15. Vitamin C (Ascorbic Acid) Biochemistry
  16. Vitamin C (Ascorbic Acid) Deficiency and Excess
  17. Vitamin D Biochemistry
  18. Vitamin D Deficiency and Excess
  19. Vitamin E (Tocopherol/Tocotrienol)
  20. Vitamin K Biochemistry
  21. Vitamin K Deficiency
  22. Zinc
  23. Kwashiorkor and Marasmus


Vitamin K is a fat-soluble vitamin synthesized by intestinal bacteria. Vitamin K is activated by the enzyme epoxide reductase to its reduced form, which acts as a cofactor for gamma-carboxylation of glutamic acid residues on blood clotting proteins. Therefore, Vitamin K plays an important role in coagulation (formation of blood clots), as there are a number of such vitamin K-dependent coagulation factors: including factors II, VII, IX, X, as well as protein C and S.

Key Points

  • Vitamin K
    • Fat-soluble compounds synthesized by intestinal flora
      • Includes phytomenadione, phylloquinone, phytonadione
      • Vitamin K Deficiency typically caused by fat malabsorption
    • Activated by epoxide reductase to reduced form
      • Active Vitamin K is a cofactor for the y-carboxylation of glutamic acid residues needed to synthesize blood clotting factors
        • Vitamin K-dependent proteins include Factors II, VII, IX, X, proteins C and S
      • Warfarin (Coumadin) inhibits epoxide reductase, blocking vitamin K-mediated gamma-carboxylation

Find Vitamin K Biochemistry and other Vitamins among Pixorize's visual mnemonics for the USMLE Step 1 and NBME shelf exams.