Fat Soluble

Question 1

Vitamins A sources

Answer 1

Vitamins A belong to rentinoid family.
Provitamins A (such as beta-carotene) belongs to carotenoids family (can be cleaved to make 2 molecules of vitamin A).
Transported to liver via chylomicrons and stored for 6-12 months.

Sources: liver, dark green and yellow vegetables.

Question 2

Vitamin A functions

Answer 2

Vision: all-trans retinal in retina converted to 11-cis retinal. Binds to opsin and forms rhodopspin. Light –> 11-cis converts into all-trans and opsin dissociates (cGMP nerve impulse). Free all-trans is converted back into 11-cis to repeat cycle.

Gene Regulation: epithelial cells inside body don’t kertinize because all-trans retinoic acid suppresses nuclear receptors. Lack of all-trans retinoic acid –> keratinization.

Antioxidant: reduces risk of cancer

Question 3

Vitamin A etiology

Answer 3

Hypervitaminosis: toxic and teratogenic.

Deficiency: xerophthalmia, keratinization of the cornea which causes blindness. Night blindness, follicular hyperkeratosis, anemia.

Special Needs: premature infants (low reserves), fat malabsorption syndromes

Question 4

Vitamin D sources

Answer 4

Sources:

endogenous from skin metabolite 1-dehydrocholestrol which can turn into cholcalciferol (inactive D3)

dietary from fortified foods with ergocalciferol (inactive D2). Saltwater fish, liver, egg yolks, fortified foods.

Must be activated viz hydroxlation in the liver (25-OH-cholecalciferol) and then kidney (1,25-diOH-cholecalciderol)

Question 5

Vitamin D function

Answer 5

Acting alone: induces synthesis of protein for Ca adsorption in the intestines.

Acting synergistically with PTH: bone resorption (release of calcium) and inhibit calcium excretion from the kidney

Question 6

Vitamin D etiology

Answer 6

Deficiency in children: rickets (don’t mineralize Ca when bones are growing - bowlegged)

Deficiency in adults: osteomalacia (painful unmineralization of bone)

Special needs: fat malabsorption syndromes, corticosteroids, anti-convulsants

Excess: kidney damage and mineralization of soft tissue

Question 7

Vitamin E sources

Answer 7

Sources: vegetable oils

Eight different forms but only alpha-tocopherol form is active in humans. Liver preferentially re-secretes alpha form via hepatic alpha tocopherol tranfer protein and metabolizes other forms.

Question 8

Vitamin E function

Answer 8

antioxidant

Question 9

Vitamin E etiology

Answer 9

increased fragility of RBC membranes

Question 10

Vitamin K sources

Answer 10

Sources: intestinal flora produce 1/2 RDA (like biotin!)

Question 11

Vitamin K function

Answer 11

cofactor in y-carboxylation of pregoagulation factors (2,7,9,10) and bone proteins.

Question 12

Vitamin K etiology

Answer 12

Deficiency: hemorrhage
Special needs: parenteral nutrition, fat malabsorption syndrome, liver dysfunction, wide broadspecturm antibiotic therapy (wipes out GI flora), Coumadin counteraction

BABIES: newborns have low liver storage and a sterile GI, and breast milk is low in K. Hemorrhagic disease of newborn. Parenteral prophylatic vit K dose at birth.