Vitamin A Flashcards
How many carotenoids can convert to vitamin A
About 50 (out of hundreds)
Does “real” vitamin A come from plants or animals
Animal sources only
Do carotenoids come from plants or animals
Plant sources only
What is the most potent (active/”real”) form of vitamin A
All-trans retinol
What is pre-vitamin A
Retinols
What are pro-vitamin A
Carotenes
What has actual antioxidant activity
Carotenes
What are the 3 active forms of vitamin A
All-trans retinol, all-trans-retinal, all-trans retinolic acid
What is the ester form of vitamin A
Retinyl palmitate
What are carotenoids that have high antioxidant activity but are not pro-vitamin A
Lycopene, lutein, zeaxanthin
How is vitamin A absorbed
Free carotene and free retinol; similar to vitamin E
Where is carotene cleaved
Liver or small intestines
Where is retinol stored
Liver (as retinyl esters)
What two molecules travel with Retinol and RBP in the blood
Transthyretin (synthesized in liver) and thyroid hormone
Which retinoids can interconvert
Retinal and retinol
What does retinal convert to (irreversible)
Retinoic acid
Which retinoid is involved in vision (rhodopsin)
Retinal
Which retinoid is involved in gene expression and cell differentiation
Retinoic acid
Which retinoid is involved in growth
Retinol
Which retinoid is involved in reproduction
Retinol and retinoic acid
Which retinoid increases osteoclast activity
Retinol (not easy from food)
Which population is susceptible to vitamin A toxicity
Arctic (polar bear and whale!)
What binds to retinol once in the cells (pigment epithelium)
Cellular RBP
Where does retinal function in the eye
Photoreceptor
