Vitamin A

Question 1

RE

Answer 1

retinol equivalent

6mcg of carotenoid = 1mcg of retinol

Question 2

RAE

Answer 2

retinol activity equivalent
I mcg RAE requires twice as much beta-caroteen than thought before (12mcg)
and 24mcg of other carotenoids

newer conversion rates

Question 3

retinol

Answer 3

colorless form
animal products
actual vitamin form

Question 4

carotene

Answer 4

colored form

vegetable products

Question 5

retinal

Answer 5

produced from cleavage of carotenoid like beta-caroteen

Question 6

retinol

Answer 6

reduction of retinal = retinol

Question 7

retinoic acid

Answer 7

oxidation of retinal = retinoic acid

Question 8

“vitamin A”

Answer 8

refers any of the chem forms of retinol, though technically only the alcohol form

Question 9

source of vitamin a

Answer 9

carotenoids of plants; dark grn and yellow fruits and vegetables
animals convert carotenoid food -> retinol or its derivatives; egg yolk, milk fat, liver, kidney

Question 10

what forms of vit A do we actually use?

Answer 10

retinol
retinal
retinoic acid

(vegs contain carotenoids = precursors)

Question 11

chemical form that binds the protein opsin

Answer 11

retinal (aldehyde form)
forms a Schiffs base w primary aa grp of a lysine residue
= rhodopsin
when light hits it the retinal form is released and a reductase is req to re-initiate formation of the visual pigment

Question 12

role of retinoic acid

Answer 12

hormone
differentiation of epithelial cells into mucous secreting cells (esp in eye, also lungs & gut)
retinoic acid/retinol - suppress keratin formation

Question 13

other roles of vit A (besides vision)

Answer 13

maintaining immune competence
maintenance of epithelial tissues as barrier (these are independent of each other)
hematopoiesis
bone growth
reproduction
early embryonic death when enzyme responsible for forming retinoic acid is absent
cancer tx

Question 14

follicular hyperkeratosis

Answer 14

goose bump appearance to skin

mild vit a deficiency

Question 15

xerophthalmia

Answer 15

night blindness -> total blindness
due to vit A deficiency
due to inadequate pigment in retina

Question 16

bitot’s spots

Answer 16

building up of desquamated, keratinized epithelial cells

Question 17

xerosis

Answer 17

thickening of the conjunctiva, can also see inflitration and haziness of the cornea
dryness due to lack of mucous production too

Question 18

dealing w vita D deficiency

Answer 18

supplimentation

Question 19

vita toxicity

Answer 19

lipid-sol so can be stored in lrg amts
excess free retinol lyses membranes

acute overdoes - 300mg can cause acute illness or death

chronic od - excessive supp with preformed vita a (beta-carotene not known to be toxic)
7.5-9 mg/day is limit for adults

teratogenic