Exam - Vitamin A

Question 1

supplement label for Vit A

Answer 1

supports night vision, eyesight and skin health

Question 2

what is Vit A a general term for

Answer 2

retinoids

Question 3

what are the major forms of Vit A in the body

Answer 3

retinol
retinal
retinoic acid
retinyl ester

Question 4

what are precursors for Vit A

Answer 4

carotenes (provitamin A)

Question 5

what are carotenes

Answer 5

type of carotenoid - pigments produced in plants

Question 6

what are animal livers rich in

Answer 6

retinol and retinyl ester

Question 7

what are orange and dark green vegetables rich in

Answer 7

B-carotene

Question 8

what are retinyl esters rich in

Answer 8

milk and eggs

Question 9

what is retinyl ester made of

Answer 9

retinol + fatty acid

Question 10

what does retinyl esterase do

Answer 10

cleaves the fatty acid from retinol for absorption

Question 11

what are retinol and B-carotene incorporated into

Answer 11

mixed micelles

Question 12

how are retinol and B-carotene absorbed

Answer 12

passive diffusion

Question 13

what do low retinol-RBP stimulate

Answer 13

hepatic retinyl esterase

Question 14

why does retinol always travel with RBP

Answer 14

it is an alcohol and would otherwise degrade cells

Question 15

what percentage of dietary retinol is absorbed

Answer 15

70-90%

Question 16

what percentage of B-carotene is absorbed

Answer 16

20-50%

Question 17

2 fates of B-carotene

Answer 17

1. incorporated into chylomicrons as is
2. converted into a retinyl ester in intestinal cells and then incorporated into chylomicrons

Question 18

what does liver RBP synthesis depend on

Answer 18

persons Vit A status

Question 19

what is retinoic acid important for

Answer 19

the control of growth hormone expression

Question 20

what is growth hormone important for

Answer 20

growing and differentiating tissues

Question 21

what is keratin

Answer 21

major protein in all epithelial cells whose expression is regulated by RA

Question 22

what occurs in stem cells when vitamin A is present

Answer 22

1. RA differentiates the stem cells into epithelial cells
2. mucus secretion and keratinization to determine how cells will divide/function

Question 23

how often are cells replaced with stem cells

Answer 23

every 3-5 days

Question 24

what occurs in stem cells when vitamin A is deficient

Answer 24

poor differentiated function
keratinization but little mucus secretion

Question 25

what can occur with a vitamin A deficiency and impaired epithelial cell differentiation

Answer 25

in cornea: Xerophthalmia
in lungs: respiratory infection
in GI tract: diarrhea
in skin: folliculosis

Question 26

how many cases of blindness are there per year due to vitamin A deficiency and impaired epithelial cell differentiation

Answer 26

0.5 million

Question 27

how many deaths per year are there due to vitamin A deficiency and impaired epithelial cell differentiation

Answer 27

1-3 million

Question 28

what is xerophthalmia

Answer 28

not enough mucus to form protective layer on cornea so viruses and bacteria can penetrate

Question 29

consequences of vitamin A deficiency

Answer 29

1. night blindness
2. impaired epithelial cell differentiation
3. impaired growth
4. impaired fertility
5. fetal development defects (deficiency and toxicity)

Question 30

how many children are Vit A deficient

Answer 30

100-140 million

Question 31

what is RAE

Answer 31

retinol activity equivalents

Question 32

why is there no upper limit for B-carotene

Answer 32

it prevents deficiency but does not cause toxicity - only used when we need it

Question 33

what is the most severe consequence of vitamin A toxicity

Answer 33

liver cell death