Lecture 13 - Antioxidants Flashcards by Delayne van Dijk

What is the role of antioxidants?

To protect cells from oxidative damage

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What are the agents that protect from oxidative damage?

Vitamins quench the radicals

Minerals act as cofactors for enzymes

Phytochemcials

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What is a free radical?

Something with an unpaired electron which damages lipids DNA RNA and proteins

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What neutralizes free radicals?

Antioxidants

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What is the definition of quench?

To get rid of, eliminate

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What can antioxidants be thought of?

Dominos, a vitamin would sit inform of the domino to prevent the others from following

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Why are minerals required for antioxidants?

They themselves aren’t antioxidants, but they are just required for the function

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What creates free radicals?

Any normal reaction in the body

Sun

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What are the available forms of vitamin A?

Retinyl Esters: True vitamin a

Beta Carotene: Precursor for vitamin a (not true)

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Where are Retinyl esters in the body?

Bonded to fat in the body. Esters will separate from fat to just have retynil

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What is the storage form of Vitamin a

Retinal

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What is retinol involved in?

Vision related

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How do we end up with retinal?

Retinyl (from animal foods) > Converted to retinol > converted into retinal

Beta-carotene (from plants) > Converted to retinal

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In the body, what are the different conversions of all the retinoids?

Retinol< >Retinal> Retanoic acid

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What happens when we have too much retinal?

It can be converted back to retinol

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What is the hormone version of vitamin a?

Retanoic Acid

-involved in DNA, transcription, Cell division, growth, reproduction

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Do carotenoids all have the same antioxidant activity?

Yes, but not all of them are converted to vitamin a

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What is the pathway for vitamin a once it has been ingested?

It is fat soluble and will end up in the chylomicrons then into the lymph and blood. Once in the blood it binds to binding proteins to be carried within the body

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Where is vitamin a role in protein synthesis and cell differentiation

Takes place in epithelial cells on the skin and in the mucos membranes. Vitamin a is there to make sure those cells divide properly
-promotes differentiation of epithelial and goblet cells

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How does vitamin a help with reproduction and growth?

Sperm development
Fetal development
Bone remodelling
Failure of growth in children

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What does vitamin a deficiency look like?

Vitamin a status

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What is vitamin a status?

Amount of vitamin a for you to use is dependant on how much is in your liver as well as your protein status

What happens to vitamin a when you don’t have enough protein?

It won’t transport vitamin a

What is vitamin a deficiency dependent on?

Vitamin a status and protein tatus

Where is vitamin a stored?

In the liver

What results from a vitamin a deficiency?

- Infectious disease - Night blindness (lack of rhodopsin and inability to recover from changes in light) - Xerophthalmia (total blindness due to drying and softening of cornea) - Keratinization

How does vitamin a toxicity occur?

When binding proteins in the blood become swamped, the vitamin isn't excreted quickly so the free vitamin a can cause damage -not seen with beta-carotene

Why isn't vitamin a a treatment for acne?

Vitamin a itself is not used as a treatment for acne but the retinoid used to treat acne have no vitamin a activity

What are some sources of beta carotene?

Yellow+Green veggies -any vegetable really Preformed vitamin a in any animal protein with some fat

What is RAE and what are the conversions??

Retinal activity equivalent 1microgram of preformed vitamin a= 1RAE 12micrograms of beta-carotene= 1RAE

What is vitamin e role as an antioxidant?

Primary defender against free radicals - prevents more free radicals from producing more free radicals - cell membranes and other lipids - oxidizes LDL

What is the other name for vitamin e?

Tocopherol | -alpha is the main type

How does vitamin e reduce the oxidization of LDL?

Vitamin e sits in LDL and reduced the oxidation of LDL | -blood vessels see the oxidized LDL as the enemy

Can you become vitamin e deficient?

Primary deficient is rare (fat malabsorption mainly) | -Can present in infants

What happens when you are vitamin e deficient?

Red blood cells break open due to oxidization of PUFAs in RBC membranes -causes Erythrocyte Hemplysis

Can you become toxic from vitamin e?

Very rare, liver regulated vitamin e | -may interfere with blood clotting because vitamin e is a blood thinner, thus interfering with vitamin k

What is the UL for vitamin e?

set 65x higher than the recommended value | -based on alpha tocopherol

What happens to vitamin e when there is an increase if PUFA?

There is an increase need for vitamin e

What is a source of vitamin e?

Mostly vegetable oils | -easily destroyed by heat and oxidation

What is vitamin c role in the body as an antioxidant?

Loses electrons easily to stop free radical damage -enhances iron absorption Cofactor for collagen -facilitates the binding of collagen fibres Stress -adrenal glands secrete vitamin c

What is the real name of vitamin c?

ascorbic acid | -anti scurvy

How much vitamin c do we need to prevent scurvy and to saturate tissue

10mg/day to prevent scurvy 100mg/day to saturate tissues

Why do smokers need more vitamin c?

Smokers are ingesting more chemicals that cause damage, in order to counteract the free radicals, more vitamin c is needed

What is the RDA for vitamin c?

It is set 7x higher than the amount deeded to prevent scurvy

Why is vitamin c harmful for kidneys?

Vitamin c is not stored in the body, and is excreted through the kidneys. If too much is being secreted it could damage kidneys

What does vitamin c deficiency look like?

Scurvy: bleeding gums and breaking capillaries inadequate collagen, wound heal thing stops, loose teeth, dry skin

What does vitamin c toxicity look like?

Very rare | -GI distress, diarrhea

What does vitamin c have adverse effects on?

Iron overload

Why is Se important in antioxidants?

Part of glutathione peroxidase | -works synergistically with vitamin E

Where do you find Se?

Found in soils and leaches into foods In some amino acids

Can you become deficient in Se?

Yes, but rare, ,most Canadians meet the RDA for Se | -UL set

Which vitamins work synergistically with each other?

E with Se E with A C with E -they don't work in isolation

What are the 2 lines of defence against free radicals?

1. Antioxidant enzyme defence system | 2. Antioxidant nutrients including photochemicals

What is atherosclerosis?

When LDL is oxidized to atherosclerosis