Vitamins and Coenzymes
Vitamin - definition
• An organic compound required as a nutrient in tiny amounts by an
organisms.
• It cannot be synthesized in sufficient quantities by an organism, and
must be obtained from the diet.
• Vitamins have diverse biological function:
– hormone-like functions as regulators of mineral metabolism (vit. D),
– regulators of cell and tissue growth and differentiation (some forms of
vit. A)
– antioxidants (vit. E, C)
– enzyme cofactors (tightly bound to enzyme as a part of prosthetic
group, coenzymes)
Vitamin classification
, Lipid-soluble vitamins (A, D, E and K)
• hydrophobic compounds, absorbed efficiently with lipids,
• transport in the blood in lipoproteins or attached to specific binding
proteins
Water-soluble vitamins - 8 B vitamins and vitamin C
• Function: mainly as enzyme cofactors,
• hydrophilic compounds dissolve easily in water,
• not readily stored, excreted from the body,
• their consistent daily intake is important.
• Many types of water-soluble vitamins are synthesized by bacteria.
Vitamin A
•Biologically active forms - retinoids: retinol, retinal, retinoic acid.
•Major vit. A precursors(provitamins) → plants carotenoids.
• Animal sources: cod liver oil, meat, egg, milk and dairy product
• Plant sources: carrot, broccoli, spinach, papaya and apricots
• Vitamin A has a function in vision and its deficiency leads to night
blindness.
• Necessary for the function and maintenance of epithelial tissues.
Vitamin D
• Sources of Vitamin D:
1. Diet: Ergocalciferol (vitamin D2), found in plants and mushrooms, and
cholecalciferol (vitamin D3), found in animal tissues particularly fish and
liver, are sources of preformed vitamin D activity.
2. Endogenous vitamin precursor: 7- Dehydrocholesterol, an
intermediate in cholesterol synthesis, is converted to cholecalciferol in
the dermis and epidermis of humans exposed to sunlight.
Vitamin - definition
• An organic compound required as a nutrient in tiny amounts by an
organisms.
• It cannot be synthesized in sufficient quantities by an organism, and
must be obtained from the diet.
• Vitamins have diverse biological function:
– hormone-like functions as regulators of mineral metabolism (vit. D),
– regulators of cell and tissue growth and differentiation (some forms of
vit. A)
– antioxidants (vit. E, C)
– enzyme cofactors (tightly bound to enzyme as a part of prosthetic
group, coenzymes)
Vitamin classification
, Lipid-soluble vitamins (A, D, E and K)
• hydrophobic compounds, absorbed efficiently with lipids,
• transport in the blood in lipoproteins or attached to specific binding
proteins
Water-soluble vitamins - 8 B vitamins and vitamin C
• Function: mainly as enzyme cofactors,
• hydrophilic compounds dissolve easily in water,
• not readily stored, excreted from the body,
• their consistent daily intake is important.
• Many types of water-soluble vitamins are synthesized by bacteria.
Vitamin A
•Biologically active forms - retinoids: retinol, retinal, retinoic acid.
•Major vit. A precursors(provitamins) → plants carotenoids.
• Animal sources: cod liver oil, meat, egg, milk and dairy product
• Plant sources: carrot, broccoli, spinach, papaya and apricots
• Vitamin A has a function in vision and its deficiency leads to night
blindness.
• Necessary for the function and maintenance of epithelial tissues.
Vitamin D
• Sources of Vitamin D:
1. Diet: Ergocalciferol (vitamin D2), found in plants and mushrooms, and
cholecalciferol (vitamin D3), found in animal tissues particularly fish and
liver, are sources of preformed vitamin D activity.
2. Endogenous vitamin precursor: 7- Dehydrocholesterol, an
intermediate in cholesterol synthesis, is converted to cholecalciferol in
the dermis and epidermis of humans exposed to sunlight.
