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Metabolism Exam 4 > Vitamin A > Flashcards

Vitamin A Flashcards

1
Q

How many carotenoids can convert to vitamin A

A

About 50 (out of hundreds)

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2
Q

Does “real” vitamin A come from plants or animals

A

Animal sources only

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3
Q

Do carotenoids come from plants or animals

A

Plant sources only

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4
Q

What is the most potent (active/”real”) form of vitamin A

A

All-trans retinol

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5
Q

What is pre-vitamin A

A

Retinols

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6
Q

What are pro-vitamin A

A

Carotenes

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7
Q

What has actual antioxidant activity

A

Carotenes

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8
Q

What are the 3 active forms of vitamin A

A

All-trans retinol, all-trans-retinal, all-trans retinolic acid

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9
Q

What is the ester form of vitamin A

A

Retinyl palmitate

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10
Q

What are carotenoids that have high antioxidant activity but are not pro-vitamin A

A

Lycopene, lutein, zeaxanthin

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11
Q

How is vitamin A absorbed

A

Free carotene and free retinol; similar to vitamin E

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12
Q

Where is carotene cleaved

A

Liver or small intestines

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13
Q

Where is retinol stored

A

Liver (as retinyl esters)

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14
Q

What two molecules travel with Retinol and RBP in the blood

A

Transthyretin (synthesized in liver) and thyroid hormone

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15
Q

Which retinoids can interconvert

A

Retinal and retinol

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16
Q

What does retinal convert to (irreversible)

A

Retinoic acid

17
Q

Which retinoid is involved in vision (rhodopsin)

A

Retinal

18
Q

Which retinoid is involved in gene expression and cell differentiation

A

Retinoic acid

19
Q

Which retinoid is involved in growth

A

Retinol

20
Q

Which retinoid is involved in reproduction

A

Retinol and retinoic acid

21
Q

Which retinoid increases osteoclast activity

A

Retinol (not easy from food)

22
Q

Which population is susceptible to vitamin A toxicity

A

Arctic (polar bear and whale!)

23
Q

What binds to retinol once in the cells (pigment epithelium)

A

Cellular RBP

24
Q

Where does retinal function in the eye

A

Photoreceptor

25
Q

What makes up rhodopsin

A

Opsin and retinal

26
Q

What section of DNA uses retinoic acid to induce transcription (synthesize mRNA)

A

Retinoic Acid Response Element (RARE)

27
Q

At what unit is the RDA for vitamin A set

A

Retinol Activity Equivalent (RAE)

28
Q

What is 1 RAE set at

A

1ug retinol

29
Q

How much supplemental beta-carotene converts to 1ug retinol

A

2ug

30
Q

How much dietary beta-carotene converts to 1ug retinol

A

12ug

31
Q

How much other pro-vitamin A carotenes to 1ug retinol

A

24ug

32
Q

What is the IU –> RAE conversion for supplemental and food retinol and supplemental beta-carotene

A

3.33IU

33
Q

What is the RDA for vitamin A

A

900ug/3000 IU men, 700ug/2300IU women

Metabolism Exam 4 (5 decks)

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