FNDH 620 MAIN CORE ALL QUESTIONS AND ANSWERS
SURE A+
✔✔Cobalamin (B12) function - ✔✔1) cofactor for methionine synthase:
methylcobalamin required for function of folate-dependent methionine synthase
2) Transfer of adenosine group in 2 reactions:
- leucine aminomutase
-L-methylmalonyl -CoA mutase to succinyl-CoA
3) Maintenance of CNS (including brain and spinal cord) -> production of myelin sheath
of nerve tissue
✔✔Why is succinyl-CoA important? - ✔✔- required for synthesis of heme
- important role in producing odd chain fatty acids and proteins
✔✔PQ: Why is the RDA for vitamin b12 so low? - ✔✔- in the liver, free cobalamin can
be stored for years
- very little b12 in the body is degraded
- whole body turnover is about 0.1% daily
✔✔Cobalamin (B12) deficiency: - ✔✔1) megaloblastic anemia
2) neuropathy
3) high homocysteine -> increase risk of heart disease
✔✔PQ: High dietary folate may cure megaloblastic anemia caused by: - ✔✔folate and
B12 deficiency
✔✔Why is the tolerable upper level intake of folic acid important for b12 deficiency? -
✔✔high doses of folic acid can correct megaloblastic anemia caused by b12 deficiency
(which is the first sign of b12 deficiency) and if it is not corrected could lead to
neuropathy
✔✔Is b12 toxic? - ✔✔no and it has no UL
✔✔How are fat-soluble vitamins similar to lipids? - ✔✔- absorption requires bile salts
- transported by chylomicrons
- store in liver and fatty tissue for long periods of time
- eliminated slowly
- generally toxic if consumed in excess
✔✔List the fat soluble vitamins - ✔✔Vitamins A, D, E, K
✔✔Group of compounds containing all-trans retinol activity: - ✔✔Vitamin A- retinol,
retinal, retinoic acid, retinyl esters, provitamin A carotenoids
, ✔✔Group of compounds that are precursors for vitamin A: - ✔✔provitamin A
carotenoids- alpha-carotene, beta-carotene, beta-cryptoxanthin
✔✔Beta-carotene - ✔✔can be oxidized to two retinals and then reduced to retinol by
retinal reductase via NADPH
✔✔Due to less bioavailability and low enzyme activity, at what rates are the provitamin
A carotenoids converted to vitamin A? - ✔✔beta-carotene: 1/12
alpha-carotene and beta-cryptoxanthin: 1/24
✔✔PQ: Formation of retinol from beta-carotene requires which B vitamin? - ✔✔Niacin
✔✔Vitamin A sources - ✔✔- liver
- milk
-egg
-yolk
- deep green and yellow fruits and vegetables
✔✔PQ: T/F Dietary fat is not very important regarding the digestion and absorption of
pre- and provitamin A forms. - ✔✔False
✔✔What diminishes carotenoid absorption? - ✔✔Fiber (especially pectin) and
excessive vitamin E intake
✔✔Before absorption, what is cellular retinal and retinol bound to? - ✔✔Cellular Retinol
Binding Protein II
✔✔How is retinol stored in the liver? - ✔✔retinyl esters
✔✔Vitamin A is essential for - ✔✔- vision
- cellular differentiation
- growth
- reproduction
-bone development
- immune function
✔✔Vitamin A and vision: - ✔✔- cis-retinal is bound to opsin which is needed to form
rhodopsin in the rods of the eye
- cis-retinal is isomerized to trans-retinal in the eye which send signals to the brain to
see
- trans-retinal is then recycled back into cis-retinal
✔✔PQ: Within the nucleus, retinoic acid binds to _______ - ✔✔Retinoic acid receptors
(RAR) and retinoid X receptors (RXR)
SURE A+
✔✔Cobalamin (B12) function - ✔✔1) cofactor for methionine synthase:
methylcobalamin required for function of folate-dependent methionine synthase
2) Transfer of adenosine group in 2 reactions:
- leucine aminomutase
-L-methylmalonyl -CoA mutase to succinyl-CoA
3) Maintenance of CNS (including brain and spinal cord) -> production of myelin sheath
of nerve tissue
✔✔Why is succinyl-CoA important? - ✔✔- required for synthesis of heme
- important role in producing odd chain fatty acids and proteins
✔✔PQ: Why is the RDA for vitamin b12 so low? - ✔✔- in the liver, free cobalamin can
be stored for years
- very little b12 in the body is degraded
- whole body turnover is about 0.1% daily
✔✔Cobalamin (B12) deficiency: - ✔✔1) megaloblastic anemia
2) neuropathy
3) high homocysteine -> increase risk of heart disease
✔✔PQ: High dietary folate may cure megaloblastic anemia caused by: - ✔✔folate and
B12 deficiency
✔✔Why is the tolerable upper level intake of folic acid important for b12 deficiency? -
✔✔high doses of folic acid can correct megaloblastic anemia caused by b12 deficiency
(which is the first sign of b12 deficiency) and if it is not corrected could lead to
neuropathy
✔✔Is b12 toxic? - ✔✔no and it has no UL
✔✔How are fat-soluble vitamins similar to lipids? - ✔✔- absorption requires bile salts
- transported by chylomicrons
- store in liver and fatty tissue for long periods of time
- eliminated slowly
- generally toxic if consumed in excess
✔✔List the fat soluble vitamins - ✔✔Vitamins A, D, E, K
✔✔Group of compounds containing all-trans retinol activity: - ✔✔Vitamin A- retinol,
retinal, retinoic acid, retinyl esters, provitamin A carotenoids
, ✔✔Group of compounds that are precursors for vitamin A: - ✔✔provitamin A
carotenoids- alpha-carotene, beta-carotene, beta-cryptoxanthin
✔✔Beta-carotene - ✔✔can be oxidized to two retinals and then reduced to retinol by
retinal reductase via NADPH
✔✔Due to less bioavailability and low enzyme activity, at what rates are the provitamin
A carotenoids converted to vitamin A? - ✔✔beta-carotene: 1/12
alpha-carotene and beta-cryptoxanthin: 1/24
✔✔PQ: Formation of retinol from beta-carotene requires which B vitamin? - ✔✔Niacin
✔✔Vitamin A sources - ✔✔- liver
- milk
-egg
-yolk
- deep green and yellow fruits and vegetables
✔✔PQ: T/F Dietary fat is not very important regarding the digestion and absorption of
pre- and provitamin A forms. - ✔✔False
✔✔What diminishes carotenoid absorption? - ✔✔Fiber (especially pectin) and
excessive vitamin E intake
✔✔Before absorption, what is cellular retinal and retinol bound to? - ✔✔Cellular Retinol
Binding Protein II
✔✔How is retinol stored in the liver? - ✔✔retinyl esters
✔✔Vitamin A is essential for - ✔✔- vision
- cellular differentiation
- growth
- reproduction
-bone development
- immune function
✔✔Vitamin A and vision: - ✔✔- cis-retinal is bound to opsin which is needed to form
rhodopsin in the rods of the eye
- cis-retinal is isomerized to trans-retinal in the eye which send signals to the brain to
see
- trans-retinal is then recycled back into cis-retinal
✔✔PQ: Within the nucleus, retinoic acid binds to _______ - ✔✔Retinoic acid receptors
(RAR) and retinoid X receptors (RXR)
