Vitamin A Flashcards by Charlotte Schrimsher

What are all the different retinoids and their functional groups?

RetinOL= alcohol group
RetinAL= aldehyde group
Retinoic acid= carboxylic acid group
Retinyl ester= ester group

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T or F
Retinoids are fat soluble but caretinoids aren’t

False, both fat soluble

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Over ____ caretinoids are found in nature and most are ___

700
Antioxidants

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What are the provitamins or caretinoids that can turn into vitamin A?

B-carotene
A-carotene
B-cyrptoxanthin

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What are the nonprovitamin A caretinoids?

Lycopene
Lutein
Zeaxanthin
Canaxanthin

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Plants, some seafood, and some fish are examples of ___ which make it unique on top of being a red orange carotenoid

Canthaxanthin

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What is the major site where caretinoids turn into retinoids? What are some other sites it can happen at?

Enterocyte is major site
Liver
Adipose
Lungs
Kidneys
Others
(Remember L KALE)

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What enzyme concerts careotinoids to retinoids?

Beta carotene oxygenate 1 (BCO1) but there are also others

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T or F
Beta carotene gets broken down into 2 types of retinal

True

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What is the RDA for females and males 14-70 for vitamin A?

F= 700 ug
M= 900 ug

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1 IU is equivalent to ___ micrograms of retinol

0.3

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What as the RDA for vitamin A for pregnant and lactating people older than 19?

Pregnancy= 770
Lactation= 1300

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T or F
Vitamin A can be a teratogen in large amounts

True

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Avoid taking a multivitamin that contains more than ____ IU/ ___ug of vitamin A for pregnant women

500 IU
1500 ug

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What is the best absorbed caretinoid?

Beta carotene

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Supplement form of ___ has the best RAE conversion rate

Beta carotene

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Conversion of beta carotene to retinal is about ___% from supplements

50%

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Principal forms of preformed vitamin A in supplements are ____ and ____

Retinyl palmitate
Retinyl acetate
(B-carotene also used)

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Why is it better to get vitamin A from beta carotene rather than retinyl?

No toxicity or teratogen for b-carotene so you can avoid problems

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What are food sources of retinoids?

Liver (exceeds UL)
Herring
Salmon
Tuna
Egg
Cheese
Cows milk (fortified)

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What are food sources of carotenoids?

Spinach
Kale
Carrots
Cantaloupe
(More cooked= more careotinoids)

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Absorption of preformed vitamin A is approximately __-__% if the meal has about ____ or more grams of fat

70-90%
5-10

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Beta carotene absorption is about __-__%
Caretinoids is about __% for uncooked vegetables but processed juices containing caretinoids have about a __% absorption rate

20-50%
5%
60%

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T or F
The digestion of vitamin A happens by protein and fat associated with Vit A/ carotenoids are cleaved off, Micelles form, and then it’s absorbed into the enterocyte

True

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What micelles form?

Bile Digested lipids Vitamin A Carotenoids

What type of vitamin A is able to travel directly into the portal system? What is it bound to?

Retinoic acid Bound to albumin

Most retiniods and carotenoids are packaged into ___

Chylomicrons

Where are most retinoids stored? In what type of cells?

Liver Parenchymal cells Stellate cells (where most stored)

Why is getting to much vitamin A a problem?

Stellate cells mainly store vitamin A but there aren’t many of those cells which can lead to toxicity

What are the two proteins required for vitamin A transportation?

Retinol binding protein (RBP) Transthyretin (TTR)

The synthesis of RBP needs both ___ and __

Protein and Zn (So low of either of these can lead to impaired Vit A transportation)

___ impairs the release of vitamin A from the liver

Inflammation

In the liver vitamin A as ____ complexes with RBP and is released into the bloodstream as ____. Then that binds with ___ in the bloodstream and complexes with ___

Retinol Holo-retinol-RBP TTR Holo-retinol-RBP-TTR complexes with T4

T or F It is more complex for vitamin A to get into the bloodstream than other nutrients

True

Caretinoids are put into __ which transport caretinoids in the bloodstream

VLDL

T or F Both carotenoids and retinoids are antioxidants

False, only carotenoids

What are the functions of vitamin A?

1. Bone development/ maintenance 2. Needed for reproduction 3. Gap junction communication 4. Immune function (helps w formation of mucus) 5. Cellular differentiation, proliferation, growth 6. Maintain epithelial cells 7. Gene expression 8. Visual cycle

___ maintains both normal structure and function of epithelial cells. Some examples of epithelial cells are ___, ___, and ___

Retinoic acid Skin (keratinocytes) All internal body tracts Eyes

With a vitamin A deficiency, ___ producing cells replace mucus secreting cells in many body tissues. Some examples of mucus forming cells are ___,___,___, and ___

Keratin Skin Eyes Gastrointestinal tract Trachea

Vitamin A deficiency increases ___ and decreases ____

Infections Immune system

What are the two sets of vitamin A receptors?

Retinoid X receptor (RXR) Retinoic acid receptor (RAR)

In the nucleus RXR and RAR bind to ____ (RARE)

Retinoic acid response element

After binding with RARE, both RXR and RAR form dimer complexes. This typically leads to expression of specific genes although it can also ____ gene expression

Inhibit

The surface of the human retina contains about ___ cones and ___ rods. ___ focuses on color information while ___ focuses on greater sensitivity to low light conditions

6 million 100 million Cones Rods

Rods contain ___. What are 2 examples of that?

Rhodopsin 11-cis retinal (Vit A) Opsin (a protein)

____ is required for the enzyme that converts retinol to retinal

Zinc

What are functions of carotenoids?

Antioxidant Eye health Inhibit cell proliferation and stimulate cell differentiation May affect gene expression May improve gap junction communication

What two minerals can inhibit oxidation if the cell membrane and protect the eye against damage?

Lutein and zeaxanthin (Having more of these two can protect against AMD)

Excess Vit A seems to interfere with ___ absorption. High beta carotene intake may decrease plasma ___ concentrations

Vitamin K Vitamin E

What nutrients does vitamin A interact with?

Vitamin E, K, D, I Fe Zn Protein Fiber

____ is needed for both retinoids and carotenoid metabolism. It is a cofactor for the enzyme ___ which splits b-carotene into two ___

Iron Beta-carotene oxygenase 1 (BCO1) Two retinal

Low vitamin A status may affect the formation of ___, is associated with decreased ___ being put into __, and with finished mobilization of ___ form storage

RBC Fe RBC Fe

T or F A combination of supplemental vitamin A and iron seem to reduce anemia more effectively than either supplemental iron or vitamin A alone

True

Zinc deficiency results in decreased synthesis of ____. And is required for the enzyme that converts retinol to retinal

Retinol binding protein (RBP)

What vitamins and minerals are responsible for taste?

Zn Mg Vitamin A

What can a vitamin A deficiency cause?

Overgrowth and reduced bone degradation Decreased immune function Impaired smell/ taste Diarrhea Negatively affect eyes

Poor dark adaption, ___, ___, bitot spots, ___, and skin becoming dry and ___ are common signs of vitamin A deficiency

Night blindness Xerophthalmia (little spots of blindness from dry eyes) Blindness Scaly

T or F A vitamin A toxicity can happen form ingesting large amounts or over time

True

T or F A vitamin A toxicity can only come from supplements

False, can come from food, supplements, or certain medication

What is a large amount of vitamin A that could cause a toxicity?

15,000 mcg or about 4x the RDA

Acute and chronic vitamin A toxicity symptoms are headaches, ___,___, fatigue, and ___

Desquamation Dry skin Weight loss

T or F It is recommended that women in industrial countries avoid supplements with the active form of vitamin A

False

Which of the following are functions of vitamin A? A. Protect VLDL B. Aids in formation of RBC C. Important for bone health D. Two correct E. All correct

Which of the following are true about vitamin A and gene expression? A. RXR and RAR bind to RARE within the mitochondria B. Only used to inhibit gene expression C. RXR and vitamin D form a dimer complex D. Two correct E. All correct

How does vitamin A help with cellular differentiation? A. Vitamin A can inhibit T-reg formation and block apoptosis B. Vitamin A can induce apoptosis in keratinocytes stopping their ability to make mucus C. Vitamin A can transform immature cells into mature cells D. All correct E. None correct

Which of the following are true about the release of vitamin A from the liver? A. Holo-retinol-RBP is formed in the liver B. Holo-retinol-RBP-TTR forms in the liver before releasing into the bloodstream C. Most vitamin A is transported throughout bloodstream as part of VLDL D. Two correct E. All correct

T or F Beta carotene is best absorbed of all carotenoids and is even better absorbed if received in supplement form

True

T or F There is not a toxicity with carotenoids

False

Which are correct? A. A teratogen is something that can harm the fetus B. Rods are found in the fovea of the eye C. RXR and vitamin D bound together is an example of a heterodimer D. Two correct E. All correct

Vitamin A can be transported through the bloodstream by? A. Just TTR B. RBP with or without TTR C. Albumin D. Two correct E. All correct

Which is true? A. Micelles are important to the absorption of retinoids and carotenoids B. In the small intestinal lumen retinoids are packaged into chylomicrons C. Retinoids do not require digestion to be absorbed into the enterocyte D. Two correct E. All correct

Retinal and which protein form Rhodopsin? A. RBP B. TRR C. Opsin D. None correct

T or F Zeanthin and Lutein whether through plant foods, lean meat, or supplementation have been shown to reduce the risk of ARMD

False

Which is true? A. Inflammation impairs the release of vitamin A from the liver B. Vitamin A is only stored in the liver C. A meal that contains fat aids in the absorption of vitamin A D. Two correct E. All correct

T or F Lycopene is a carotenoid that is classified as a nonprovitamin A

True

T or F The UL of vitamin A is 3000 mcg for a 25 year old adult

True

T or F Gel forming fiber has no effect on vitamin A absorption

False

T or F Lipase is needed for both vitamin A and B12 digestion

False

T or F A function of b-cryptoxanthin is mucus formation

False

Which if the following is a food source of vitamin A? A. Liver B. Carrots C. Eggs D. Two correct E. All correct

T or F Carotenoids are not found in LDLs

False

T or F Vitamin A and B12 participate in methyl donation

False

T or F Transcriptional factors that we have covered this semester are zinc, calitriol, retinoic acid, and iodine

True

T or F Maintaining cell membrane integrity is a function shared by both retinoids and carotenoids

True