Vitamin A

Question 1

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

Answer 1

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

Question 2

source: what form is vit a mostly found in

Answer 2

retinyl esters (retinyl palmitate)

Question 3

requires the presence of _____ to be absorbed

Answer 3

bile salts and phospholipids

Question 4

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

Answer 4

1. fatty acid binding proteins

2. fatty acid transport proteins

Question 5

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

Answer 5

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

Question 6

what two enzymes are present in vit a

Answer 6

1. retinal reductase (retinal -> retinol)

2. retinal oxidase (retinal -> retinoic acid)

Question 7

metabolic pathway to liver: stored inside hepatic stellate cells

Answer 7

hypervitaminosis A occurs when stellate cells are full

Question 8

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

Answer 8

retinol binding porteins (RBP)

Question 9

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

Answer 9

retinoic acid

Question 10

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

Answer 10

glucuronic acid (kiss of death)

Question 11

what triggers metabolism in the liver cells

Answer 11

CRBP I - cellular retinol binding proteins I

Question 12

where are the two cellular retinol binding proteins

Answer 12

1. CRBP I - all tissues

2. CRBP II - small intestine

Question 13

what is the rate limiting step for retinoic acid production

Answer 13

retinol dehydrogenase

Question 14

adds glucuronic acid to both retinol and retinoic acid

Answer 14

glucuronidase

Question 15

visual cycle: cellular retinol binding protein

Answer 15

CRBP

Question 16

visual cycle: lecithin retinol acyl transferase

Answer 16

LRAT

Question 17

visual cycle: cellular retinal binding protein

Answer 17

CRALBP

Question 18

visual cycle: ______ dehydrogenase

Answer 18

11 - cis retinol

Question 19

visual cycle: interphotoreceptor retinol binding protein

Answer 19

IRBP

Question 20

visual cycle: ____ dehydrogenase

Answer 20

all-trans retinal

Question 21

retinoic acid response promotor regions are activated by

Answer 21

RAR and RXR

Question 22

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

Answer 22

activators

Question 23

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

Answer 23

repressors

Question 24

cAMP dependent protein kinase activity ____ after exposure to retinoic acid

Answer 24

increases

Question 25

retinoylation of proteins by retinoyl CoA (3):

Answer 25

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

Question 26

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

Answer 26

connexin 43

Question 27

lack of gap junctions (connexin 43) can lead to

Answer 27

uncontrolled cell growth (cancer)

Question 28

name 6 happenings of vit a deficiency

Answer 28

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

Question 29

vit a can treat acne and psoriasis

Answer 29

T

Question 30

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

Answer 30

T

Question 31

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

Answer 31

T

Question 32

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

Answer 32

60mg

Question 33

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

Answer 33

15,000 IU (teratogenic effect)