vitamin a

Question 1

group of compounds that possess the biological activity of all trans-retinol; only found in animal foods

includes: retinol, retinal, retinoic acid, retinyl ester, and synthetic analogues

Answer 1

vitamin a

Question 2

red, orange, and yellow lipid soluble pigments found mainly in plants

Answer 2

carotenoids

Question 3

beta carotene, alpha carotene, and beta cryptoxanthin

Answer 3

provitamin a

Question 4

sources of vitamin a

Answer 4

liver, dairy, eggs, fatty fish/oils

Question 5

sources of carotenoids

Answer 5

brightly colored fruits and vegetables

Question 6

oxidized form of vitamin a

Answer 6

all-trans retinal

Question 7

cleaved to form 2 molecules of retinal

Answer 7

beta-carotene

Question 8

carotenoids to vitamin a

Answer 8

beta carotene -> 2 molecules retinal –> vitamin a

Question 9

vitamin a requires

Answer 9

digestion
(retinol bound to fatty acid esters)
(retinyl esters + carotenes complexed w/ protein)

Question 10

emulsification of fat globules by

Answer 10

bile

Question 11

fat in diet assists with

Answer 11

absorption

Question 12

retinol is absorbed via

Answer 12

passive diffusion (70-90%)

Question 13

carotenoids absorbed via

Answer 13

transporters and passive diffusion (20-50%)

Question 14

carotenoids and retinoids metabolized in

Answer 14

enterocytes

Question 15

carotenoids and retinoids metabolized in enterocytes through being bound to

Answer 15

cellular-retinol binding protein (CRBP)

Question 16

how is retinol + carotenoids transported

Answer 16

esterified and incorporated into chylomicrons

Question 17

how is retinoic acid carried in blood

Answer 17

albumin

Question 18

retinol goes to lyphatic system through

Answer 18

chylomicrons

Question 19

retinoic acid goes to bloodstream through

Answer 19

albumin

Question 20

steps of vitamin a -> blood/lymph

Answer 20

1) beta-carotene is converted into 2 retinal molecules
2) CRBP 2 binds to both retinol and retinal in the intestinal cell
3) retinal is reduced to retinol by retinal/retinaldehyde reductase to from CRBP2-retinol
4) llecithin retinol acyl transferase (LRAT) esterifies a fatty acid onto the CRBP2-bound retinol to form CRBP2-retinyl palmitate
5) retinyl esterrs aer incorporated to form a chylomicron
6) chylomicrons leave intestinal cell and enter lymph system and the blood
7) retinoic acid can directly enter the blood, where it attaches to albumin for transport to the liver

Question 21

chylomicrons carry retinol and carotenoids to

Answer 21

adipose and liver

Question 22

retinol that is esterified may be stored in

Answer 22

liver (setllate cells and parenchymal cells)

Question 23

retinol transported in blood by

Answer 23

retinol-binding protein
transthyretin