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Nutritional Biochem > Vitamin A > Flashcards

Vitamin A Flashcards

1
Q

synthesis: what are the group of compounds that possess the biological activity of all trans retinol

A
  1. all-trans retinol
  2. retinal
  3. retinoic acid
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2
Q

source: what form is vit a mostly found in

A

retinyl esters (retinyl palmitate)

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3
Q

requires the presence of _____ to be absorbed

A

bile salts and phospholipids

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4
Q

what 2 protein carries are needed at the brush border for absorption

A
  1. fatty acid binding proteins

2. fatty acid transport proteins

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5
Q

what three components are needed for metabolism of vit a inside the enterocyte

A
  1. albumin retinoic acid complex (to liver)
  2. CRBP II (cellular retinol binding protein II)
  3. LRAT (lecithin retinol acyl transferase)
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6
Q

what two enzymes are present in vit a

A
  1. retinal reductase (retinal -> retinol)

2. retinal oxidase (retinal -> retinoic acid)

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7
Q

metabolic pathway to liver: stored inside hepatic stellate cells

A

hypervitaminosis A occurs when stellate cells are full

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8
Q

metabolic pathway to liver: attached to _____ and released by exocytosis from the liver

A

retinol binding porteins (RBP)

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9
Q

metabolic pathway to liver: oxidized to ____ and enters the nucleus

A

retinoic acid

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10
Q

metabolic pathway to liver: conjugation with _______ for excretion in the bile

A

glucuronic acid (kiss of death)

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11
Q

what triggers metabolism in the liver cells

A

CRBP I - cellular retinol binding proteins I

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12
Q

where are the two cellular retinol binding proteins

A
  1. CRBP I - all tissues

2. CRBP II - small intestine

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13
Q

what is the rate limiting step for retinoic acid production

A

retinol dehydrogenase

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14
Q

adds glucuronic acid to both retinol and retinoic acid

A

glucuronidase

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15
Q

visual cycle: cellular retinol binding protein

A

CRBP

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16
Q

visual cycle: lecithin retinol acyl transferase

A

LRAT

17
Q

visual cycle: cellular retinal binding protein

A

CRALBP

18
Q

visual cycle: ______ dehydrogenase

A

11 - cis retinol

19
Q

visual cycle: interphotoreceptor retinol binding protein

A

IRBP

20
Q

visual cycle: ____ dehydrogenase

A

all-trans retinal

21
Q

retinoic acid response promotor regions are activated by

A

RAR and RXR

22
Q

all retinoic acid acts as ______ when in the presence of all-trans or 9-cis-retinoic acid

A

activators

23
Q

all retinoic acid acts as _____ when in the absence of retinoic acid

A

repressors

24
Q

cAMP dependent protein kinase activity ____ after exposure to retinoic acid

A

increases

25
Q

retinoylation of proteins by retinoyl CoA (3):

A
  1. esterification to serine, theoinine, and tyrosine
  2. thio-ester to cysteine
  3. amide to lysine and arginine
26
Q

retinoic acid increased synthesis of ______ (protein that makes gap junctions)

A

connexin 43

27
Q

lack of gap junctions (connexin 43) can lead to

A

uncontrolled cell growth (cancer)

28
Q

name 6 happenings of vit a deficiency

A
  1. proliferation of immature undifferentiated cells
  2. decreased apoptosis of cancer cells (decreased caspase 9 and BCL2)
  3. inactivation of tumor suppressor genes by RXR
  4. ethanol is a competitive inhibitor of retinol dehydrogenase
  5. night blindness may be first symptom
  6. microcytic anemia
29
Q

vit a can treat acne and psoriasis

A

T

30
Q

vit a can enhance macrophage and neutrophil ability to migrate to site of infection

A

T

31
Q

antigen presenting cells may help carry out immune system functions of vit a

A

T

32
Q

what mg dose would enhance hemoglobin concentrations, decrease the prevalence of anemia, and improve the phagocytic activity of neutrophils

A

60mg

33
Q

what dose can increase the risk of birth defects in pregnant women

A

15,000 IU (teratogenic effect)

Nutritional Biochem (17 decks)

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