Vitamin A and Carotenoids

Question 1

retinoids comprise both __ and __ species that bear a structural resemblance to __, with or without the biological activity of __

Answer 1

retinoids comprise both natural and synthetic species that bear a structural resemblance to all-trans-retinol, with or without the biological activity of vitamin A

Question 2

main function of Vitamin A

Answer 2

growth factor at all stages in life

Question 3

6 biological functions of vitamin A

Answer 3

1. bone formation
2. vision
3. immune
4. cell growth and differentiation
5. reproduction
6. organ development

Question 4

In cell growth and differentiation, vitamin A becomes a __ that affects a large number of genes

Answer 4

In cell growth and differentiation, vitamin A becomes a transcription that affects a large number of genes

Question 5

vitamin A is a subgroup of __

Answer 5

vitamin A is a subgroup of retinoids

Question 6

biologically active form of vitamin A

Answer 6

all-trans retinol

Question 7

storage form of Vitamin A

Answer 7

retinyl-esters

Question 8

transport form of Vit A

Answer 8

all-trans retinol

Question 9

all-trans retinol

Answer 9

1. transport form of Vit A
2. substrate for making biologically active Vit A
3. active form of Vit A, bc it is the precursor

Question 10

oxidation of all-trans-retinol produces __ which is transported into __ and used in several __

Answer 10

oxidation of all-trans-retinol produces all-trans-retinal which is transported into cells and used in several biological pathways

Question 11

all-trans retinoic acid requireds __ to be a __ factor derived from __

Answer 11

all-trans retinoic acid requires 9-cis-retinoic acid to be a transcription factor derived from Vit A

Question 12

retinyl ester = retinol + __

Answer 12

retinyl ester = retinol + fatty acid (FA)

Question 13

retinyl esters are the __ form of vitamin A stored primarily in the __

Answer 13

retinyl esters are the storage form of vitamin A stored primarily in the liver

Question 14

retinyl-esters are the __ form of Vitamin A in __

Answer 14

retinyl-esters are the transportable form of Vitamin A in chylomicrons

Question 15

11-cis-retinal is a __ factor that controls __ and is necessary for formation of __

Answer 15

11-cis-retinal is a transcription factor that controls nocturnal vision and is necessary for formation of rhodopsin

Question 16

13-cis-retinoic acid aka __ is a __ __ factor and is a more __ form of retinoic acid

Answer 16

13-cis-retinoic acid aka accutane is a synthetic transcription factor and is a more potent/active form of retinoic acid

Question 17

carotenoid structure

Answer 17

2 retinal attached

Question 18

3 most abundant carotenoids

Answer 18

1. beta-carotene
2. alpha-carotene
3. lycopene

Question 19

__ and __ can be converted into trans-retinal

Answer 19

beta-carotene and alpha-carotene can be converted into trans-retinal

Question 20

lycopene is a __, but can’t be converted to __

Answer 20

lycopene is a essential antioxidant, but can’t be converted to vit A

Question 21

where do animals get carotenoids?

Answer 21

diet, we can’t make them de novo

Question 22

2 chemical forms of carotenoids

Answer 22

1. carotenes
2. xantophylls

Question 23

carotenes are made of __ and __ and include __, __, and __

Answer 23

carotenes are made of hydrogen and carbon and include beta and, alpha-carotene, and lycopene

Question 24

xantophylls have at least one __ and include __ and __

Answer 24

xantophylls have at least one oxygen and include beta and alpha-crypyoxanthin

Question 25

pro-vitamin definition

Answer 25

substance that can be converted to a vitamin

Question 26

Provitamin A

Answer 26

1. beta-carotene 2. alpha-carotene 3. beta-cryptoxanthin 4. alpha-cryptoxanthin

Question 27

non-provitamin A

Answer 27

1. lycopene 2. zeaxanthing 3. lutein

Question 28

main food form of vitamin A

Answer 28

retinyl esters

Question 29

2 enzymes that promote synthesis of retinyl esters

Answer 29

LRAT and ARAT

Question 30

retinoid metabolism steps overview

Answer 30

1. retinyl esters obtained from diet 2. retinyl esters to retinol 3. retinol transported into cells and oxidized into retinaldehyde 4. retinaldehyde processed

Question 31

3 fates of retinaldehyde

Answer 31

1. converted to retinoic acids (trxn factors) 2. converted to 11-cis-retinaldehyde 3. converted back into retinol then back to retinyl esters (for storage, by LRAT and ARAT)

Question 32

major dietary source of vitamin A is __ which is found in __

Answer 32

major dietary source of vitamin A is **retinyl esters** which is found in **liver, fish, dairy products, eggs**

Question 33

there are over 600 __ in plants, 50 can be metabolized to have __ activity these are called __

Answer 33

there are over 600 **carotenoids** in plants, 50 can be metabolized to have **vit A** activity these are called **pro-vitamin A**

Question 34

provitamin becomes vitamins in the

Answer 34

intestine

Question 35

main provitamin A carotenoids in human diet are

Answer 35

beta-carotene alpha-carotene beta-cryptoxanthin

Question 36

high content of carotenoids found in

Answer 36

neon foods carrots squash tomatoes papaya oranges leafy greens

Question 37

top vit A sources in US diet

Answer 37

dairy eggs fortified cereals liver fish

Question 38

top sources of provitamin A

Answer 38

carrots broccoli cateloupe squash

Question 39

carotenoids are/are not vit A carotenoids are __

Answer 39

carotenoids are/**are not** vit A carotenoids are **precursors for the synthesis of vit A**

Question 40

carotenoid RDA increases during pregnancy and lactation bc

Answer 40

cell growth

Question 41

bioavailability: food source and structure of carotenoid affect (4)

Answer 41

1. intestinal digestion 2. solubilization 3. absorption 4. metabolism in enterocytes

Question 42

some carotenoids (ie those in __) are not well absorbed bc

Answer 42

some carotenoids (ie those in **spinach**) are not well absorbed bc they are trapped in strong food matrix

Question 43

what helps release carotenoids

Answer 43

cooking

Question 44

enterocytes absorb and bio-convert 100% of __ into retinol

Answer 44

enterocytes absorb and bio-convert 100% of **supp or dietary vit A** into retinol

Question 45

enterocytes absorb and bio-convert 50% of __ into retinol

Answer 45

enterocytes absorb and bio-convert 50% of **beta-carotene** into retinol

Question 46

what has worst absorption in enterocyte

Answer 46

dietary beta-carotene dietary alpha-carotene and beta-cryptoxanthin

Question 47

dietary/supp __ is effectively absorbed and bio-converted to retinol, but supp/diet __ is less efficiently converted

Answer 47

dietary/supp **vit A** is effectively absorbed and bio-converted to retinol, but supp/diet **pro-vit A (beta-carotene)** is less efficiently converted

Question 48

vit A upper tolerable limit is only __x the DRI

Answer 48

vit A upper tolerable limit is only **2-3 times** the DRI

Question 49

upper limits of vit A cause

Answer 49

1. liver abnormalities 2. teratogenic effects 3. toxic effects in infants and children

Question 50

should we use beta-carotene and provit A supplements?

Answer 50

no bc of risks of upper limit

Question 51

4 stages of vit A digestion and absorption

Answer 51

1. dietary vit A (retinyl esters) and carotenoids **released from food by proteolysis **in stomach **aggregate with lipids** 2. in small intestine, **emulsified with lipids** and bile salts, retinyl esters are hydrolyzed by pancreatic lipases: **release retinol which will enter the enterocyte** 3. all-trans retinol in micelles (w/ bile salts) are well-absorbed (70-90%) 4. efficiency of beta-carotenoids absorption: 5-65%

Question 52

absorption of vit A requires dietary

Answer 52

lipids/fats

Question 53

absorption rate of all-trans retinol micelles

Answer 53

70-90%

Question 54

absorption rate of beta-carotenoids

Answer 54

5-65%

Question 55

all forms of vit A in the cell are

Answer 55

carried by protein

Question 56

digestion and absorption of vit A steps

Answer 56

1. ingestion of protein-bound carotenoids and retinyl esters 2. proteases (pepsin, trypsin) release vit A vitamers 3. hydrolases (esterases, lipases) remove FA from retinyl esters 4. free carotenoids and free retinol incorporated into a micelle (requires fat and bile) 5. micelle navigates layer of water and goes to membrane 6. retinol packaged into chylomicrons and shuttled into lymph

Question 57

all intracellular vit A vitamers are carried by a __ such as __

Answer 57

all intracellular vit A vitamers are carried by a **protein** such as **CRBPII**

Question 58

most retinol entering the enterocyte is converted into __ and packaged into __, and shuttled through the __ system

Answer 58

most retinol entering the enterocyte is converted into **retinyl esters** and packaged into **chylomicrons**, and shuttled through the **lymph** system

Question 59

why isn't vit A directly transported to the liver via portalc circulation

Answer 59

that would overwhelm the liver with fat

Question 60

how does retinol enter cell?

Answer 60

diffusion, it doesn't need a trasnporter