Flashcards in Vitamin A Deck (33)
Loading flashcards...
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
