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biochem block 2 > vitamins2 > Flashcards

vitamins2 Flashcards

1
Q

vit K1=

A

phylloquinone, from plants

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2
Q

vit K2=

A

menaquinone, from fish

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3
Q

menadione=

A

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

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4
Q

role of vit K in clotting

A

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

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5
Q

role of vit K in bone development

A

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

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6
Q

2 enzymes that help to recycle vit K via reduction

A
  • vit K epoxide reductase

- vit K reductase

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7
Q

inhibitors of the bit K reductases

A

warfarin

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8
Q

reason that most newborns have vit k def

A

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

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9
Q

excess menadione will cause-

A

hemolytic anemia and jaundice d/t liver toxicity

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10
Q

is intestinal synthesis of vitamin K sufficient?

A

no, also need from the diet

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11
Q

form of vitamin a that is part of visual pigment

A

11-cis retinal

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12
Q

enzyme that converts retinol –> all-trans retinal

A

retinol dehydrogenase

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13
Q

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

A

retinal isomerase

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14
Q

enzyme that converts all-trans retinal–> retanoic acid

A

retinal dehydrogenase

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15
Q

which forms of vitamin a participate in gene transcription?

A

all-trans retanoic acid (RXRs and RARs)

9-cis-retinoic acid (RXRs only)

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16
Q

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

A

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

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17
Q

what 2 elements combine to forms rhodopsin?

A
  • opsin

- 11-cis-retinal

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18
Q

describe the process of light transmission in vision

A
  • 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
19
Q

what “super family” is retinoid acid part of?

A

steroid, all have intracellular receptors with a DNA binding domain

20
Q

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

A

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

21
Q

where is vitamin a stored?

A

as retinal esters in stellate cells of the liver

22
Q

how is vitamin a released from the liver?

A

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

23
Q

how is excess vitamin a excreted?

A

add b-glucuronate and excreted in bile

24
Q

first sx of vitamin a def

A

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

25
Q

xerophthalmia occurs due to the lack of ___ (specifically)

A

retinoic acid

26
Q

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

A

b-carotene –> retinal –> retinol

mainly in intestine

27
Q

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

A

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

28
Q

excess vitamin a vs. excess b-carotene

A

excess vitamin a = liver damage, teratogen

excess b-carotene= yellow skin

29
Q

lycopene can decrease ___

A

colon CA

30
Q

lutein can help with prevention of ___

A

age related macular degeneration because it inhibits oxidation of cell membrane

31
Q

how is cholecalciferol formed?

A

reaction of 7-dehydroxycholesterol and UV light

32
Q

D2=

A

ergocalciferol (plant form)

33
Q

major circulating form of vitamin D is-

A

25-hydroxy vit D

34
Q

where is 25-hydroxy vitamin D made?

A

liver by 25-hydroxylase

35
Q

what is the active form of vitamin D?

A

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

36
Q

what is the inactive form of vitamin D?

A

24,25-dihydroxy vitamin D

37
Q

roles of calcitriol (5)

A
  • ca absorption in gut
  • Calcium/phosphate balance
  • bone growth/remodeling
  • neuro/immune function
  • gene expression (cell proliferation/death)
38
Q

at risk for vitamin D def (6)

A
  • 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)
39
Q

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

A

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

40
Q

active form of vitamin E

A

a-tocopherol

41
Q

what is aTTP?

A

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

42
Q

what is the main action of vitamin E?

A

acts as free radical scavenger and protects PUFA in membrane

43
Q

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

A

vitamin C

44
Q

consequence of vitamin E def

A

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

biochem block 2 (11 decks)

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