vitamins2

Question 1

vit K1=

Answer 1

phylloquinone, from plants

Question 2

vit K2=

Answer 2

menaquinone, from fish

Question 3

menadione=

Answer 3

synthetic form of vit K that is water soluble- converted to active form via prenylation in the liver

Question 4

role of vit K in clotting

Answer 4

cofactor for the carboxylation of glutamate to make g-carboxyglutamate, that binds Ca

Question 5

role of vit K in bone development

Answer 5

acts on osteocalcin (bone protein), to help it bind Ca

Question 6

2 enzymes that help to recycle vit K via reduction

Answer 6

• vit K epoxide reductase

- vit K reductase

Question 7

inhibitors of the bit K reductases

Answer 7

warfarin

Question 8

reason that most newborns have vit k def

Answer 8

bc intestinal bacteria is a major source of vit K and neonates are not yet colonized

Question 9

excess menadione will cause-

Answer 9

hemolytic anemia and jaundice d/t liver toxicity

Question 10

is intestinal synthesis of vitamin K sufficient?

Answer 10

no, also need from the diet

Question 11

form of vitamin a that is part of visual pigment

Answer 11

11-cis retinal

Question 12

enzyme that converts retinol –> all-trans retinal

Answer 12

retinol dehydrogenase

Question 13

enzyme that converts all-trans retinal –> 11-cis-retinal

Answer 13

retinal isomerase

Question 14

enzyme that converts all-trans retinal–> retanoic acid

Answer 14

retinal dehydrogenase

Question 15

which forms of vitamin a participate in gene transcription?

Answer 15

all-trans retanoic acid (RXRs and RARs)

9-cis-retinoic acid (RXRs only)

Question 16

what is unique about the conversion of retinal to retinoic acid?

Answer 16

rxn is irreversible, thus retinoid acid is NOT involved in the visual cycle

Question 17

what 2 elements combine to forms rhodopsin?

Answer 17

• opsin

- 11-cis-retinal

Question 18

describe the process of light transmission in vision

Answer 18

• light energy converts rhodopsin to all-trans-retinal and opsin
• transducin will activate cGMP phosphodiesterase the results in closure of Na channels
• hyperol results = signal to brain
• dehydrogenase converts all-trans back to 11-cis

Question 19

what “super family” is retinoid acid part of?

Answer 19

steroid, all have intracellular receptors with a DNA binding domain

Question 20

which form of retinoic acid receptor can form heterodimers? what can it heterodimerize with?

Answer 20

RXRs; vit D receptor, thyroid hormone receptor, PPAR receptor

Question 21

where is vitamin a stored?

Answer 21

as retinal esters in stellate cells of the liver

Question 22

how is vitamin a released from the liver?

Answer 22

bound to retinal binding protein in a “trimolecular” complex with transthyretin (pre albumin) and T4

Question 23

how is excess vitamin a excreted?

Answer 23

add b-glucuronate and excreted in bile

Question 24

first sx of vitamin a def

Answer 24

night blindness (due to lack of 11-cis-retinal)

Question 25

xerophthalmia occurs due to the lack of ___ (specifically)

Answer 25

retinoic acid

Question 26

what is the processing that happens with b-carotene? where?

Answer 26

b-carotene –> retinal –> retinol

mainly in intestine

Question 27

some b-carotene is not cleaved before it is absorbed, what happens to that?

Answer 27

it functions as an antioxidant, but has no vitamin a activity

Question 28

excess vitamin a vs. excess b-carotene

Answer 28

excess vitamin a = liver damage, teratogen

excess b-carotene= yellow skin

Question 29

lycopene can decrease ___

Answer 29

colon CA

Question 30

lutein can help with prevention of ___

Answer 30

age related macular degeneration because it inhibits oxidation of cell membrane

Question 31

how is cholecalciferol formed?

Answer 31

reaction of 7-dehydroxycholesterol and UV light

Question 32

D2=

Answer 32

ergocalciferol (plant form)

Question 33

major circulating form of vitamin D is-

Answer 33

25-hydroxy vit D

Question 34

where is 25-hydroxy vitamin D made?

Answer 34

liver by 25-hydroxylase

Question 35

what is the active form of vitamin D?

Answer 35

1,25-dihydroxy vitamin D, made by 1a-hydroxylase in kidney, aka calcitrol

Question 36

what is the inactive form of vitamin D?

Answer 36

24,25-dihydroxy vitamin D

Question 37

roles of calcitriol (5)

Answer 37

• ca absorption in gut
• Calcium/phosphate balance
• bone growth/remodeling
• neuro/immune function
• gene expression (cell proliferation/death)

Question 38

at risk for vitamin D def (6)

Answer 38

• decreased sun exposure/sunscreen
• darker skin pigments
• over 50 (dec ability to synthesize in skin/dec activation by kidney)
• breastfed infants
• CKD or liver dz
• taking meds that induce CYP450 (inactivate 1,25)

Question 39

what is the form of vitamin D supplement that must be given to pts with CKD or liver disease?

Answer 39

active form (calcitrol/1,25-dihydroxy vitamin D)

Question 40

active form of vitamin E

Answer 40

a-tocopherol

Question 41

what is aTTP?

Answer 41

a-tocopherol transfer protein, transferstocopherol from liver into VLDL for transport to other tissues

Question 42

what is the main action of vitamin E?

Answer 42

acts as free radical scavenger and protects PUFA in membrane

Question 43

what is a cofactor in regeneration of the reduced form of a-tocopherol?

Answer 43

vitamin C

Question 44

consequence of vitamin E def

Answer 44

hemolytic anemia due to increased RBC fragility; nerve degeneration in hands and feet