Flashcards in Fat soluble vitamins Deck (31):
Fat soluble vitamins
A, D, E K
Vitamin A (4)
retinol, retinal, retinoic acid and B- carotene
- function (3)
-visual pigments in retina,
-regulation of gene expression and cell differentiation
-B- carotene is an antioxidant
-yellow and dark green vegetables
1. Retinyl esters present in the diet are hydrolyzed in the intestinal mucosa, releasing retinol and free fatty acids.
2. Retinol derived from esters and from the cleavage and reduction of carotenes is reesterified chylomicrons (long-chain fatty acids in the intestinal mucosa)
3. Retinyl esters contained in chylomicron remnants are taken up by, and stored in, the
1. Retinol is released from the liver and transported to extrahepatic tissues by the plasma retinol- binding protein (RBP).
2. RBP complex attaches to specific receptors on the surface of the cells of peripheral tissues, permitting retinol to enter.
Regulation of Gene Expression (3)
1. Retinol is oxidized to retinoic acid.
2. Retinoic acid binds with high affinity to specific receptor proteins present in the nucleus.
3. The activated retinoic acid– receptor complex regulates retinoid-specific RNA synthesis.
-In the retina, retinal functions as
-the prosthetic group of the light-sensitive opsin proteins
-rhodopsin (in rods) and iodopsin (in cones)/
-When rhodopsin is exposed to light,
a series of photochemical isomerization occurs, results in release of all-trans retinal and opsin, triggers a nerve impulse that is transmitted by the optic nerve to the brain.
-Keratinization of skin
-Hypervitaminosis A: excessive intake of vitamin A
-Unbound vitamin A causes tissue damage
-Skin lesions, enlarged liver, calcification of soft tissues
Vitamin D (4)
-have a hormone- like function
-Cholecalciferol (vitamin D3)
-Ergocalciferol (vitamin D2)
-can be synthesized in the skin
Vitamin D (3)
-synthesis in the skin
1. 7- dehydrocholesterol accumulates in the skin.
2. undergoes a non-enzymatic reaction on exposure to ultraviolet light
3. pre- vitamin D3
Ergocalciferol --> found in plants
Cholecalciferol --> found in animal tissues
1. In the liver cholecalciferol is hydroxylated to form the 25-hydroxyderivative, calcidiol.
2. It is released into the circulation bound to a vitamin D binding globulin
3. In the kidney, calcidiol undergoes 1-hydroxylation
4. yield the active metabolite 1,25-dihydroxy-vitamin D (calcitriol).
-regulation in metabolism (2)
-Vitamin D’s formation is regulated by the level of plasma phosphate and calcium.
-activity is increased directly by low plasma phosphate or indirectly by low plasma calcium, which triggers the release of parathyroid hormone (PTH).
To maintain adequate plasma levels of calcium.
Vitamin D performs its function by: (3)
-increasing the uptake of calcium by the intestine
-minimizing loss of calcium by kidney
-stimulating resorption of bone when necessary
-Rickets in children
-Osteomalacia in adults
-3 compounds that have biological activity of it
-Phylloquinone: normal dietary source
-Menaquinones: synthesized by intestinal bacteria
-Menadione: can be metabolized to phylloquinone, synthetic.
-posttranslational modification of various blood clotting factors (prothrombin and blood clotting factors II, VII, IX, and X).
- synthesis of bone calcium-binding proteins
-Two proteins that contain γ-carboxyglutamate are present in bone:
osteocalcin and bone
matrix Gla protein.
found in cabbage, kale, spinach, egg yolk, and liver.
synthesized by the bacteria in the gut.
It is unusual
-Are used to reduce blood coagulation in patients at risk of thrombosis;
-The most widely used is warfarin.
-the most active is
-eight naturally occurring tocopherols.
-α –tocopherol is the most active
It is as an antioxidant in prevention of the non-enzymic oxidation of cell components by molecular oxygen and free radicals.
Vegetable oils are rich sources of vitamin E, whereas liver and eggs contain small amounts
-In humans is unknown.
-Might be in patients with severe fat mal-absorption, cystic fibrosis.
-some forms of chronic liver disease