Vitamin A Flashcards Preview

Nutritional Biochem > Vitamin A > Flashcards

Flashcards in Vitamin A Deck (33)
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1

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

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

2

source: what form is vit a mostly found in

retinyl esters (retinyl palmitate)

3

requires the presence of _____ to be absorbed

bile salts and phospholipids

4

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

1. fatty acid binding proteins
2. fatty acid transport proteins

5

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

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

6

what two enzymes are present in vit a

1. retinal reductase (retinal -> retinol)
2. retinal oxidase (retinal -> retinoic acid)

7

metabolic pathway to liver: stored inside hepatic stellate cells

hypervitaminosis A occurs when stellate cells are full

8

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

retinol binding porteins (RBP)

9

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

retinoic acid

10

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

glucuronic acid (kiss of death)

11

what triggers metabolism in the liver cells

CRBP I - cellular retinol binding proteins I

12

where are the two cellular retinol binding proteins

1. CRBP I - all tissues
2. CRBP II - small intestine

13

what is the rate limiting step for retinoic acid production

retinol dehydrogenase

14

adds glucuronic acid to both retinol and retinoic acid

glucuronidase

15

visual cycle: cellular retinol binding protein

CRBP

16

visual cycle: lecithin retinol acyl transferase

LRAT

17

visual cycle: cellular retinal binding protein

CRALBP

18

visual cycle: ______ dehydrogenase

11 - cis retinol

19

visual cycle: interphotoreceptor retinol binding protein

IRBP

20

visual cycle: ____ dehydrogenase

all-trans retinal

21

retinoic acid response promotor regions are activated by

RAR and RXR

22

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

activators

23

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

repressors

24

cAMP dependent protein kinase activity ____ after exposure to retinoic acid

increases

25

retinoylation of proteins by retinoyl CoA (3):

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

26

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

connexin 43

27

lack of gap junctions (connexin 43) can lead to

uncontrolled cell growth (cancer)

28

name 6 happenings of vit a deficiency

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

vit a can treat acne and psoriasis

T

30

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

T