Selenium Flashcards Preview

Micronutrients > Selenium > Flashcards

Flashcards in Selenium Deck (19)
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1

Organic Selenium

Selenomethionine (supplements, plants)
Selenocysteine (animals)
Methionine (sulfur)
Cysteine (sulfur)

Carbon bonding. Already replaced sulfur.

2

Selenoproteins

Selenium within the structure or Se dependent proteins.

3

Sources/ RDA

Brazil nuts
Broccoli
Garlic BEST
Wheat
Fish (if low Mercury)

>80% selenoamino acids (selenomethionine > selenocysteine)

50-90% selenate & selenite

4

Enhancers

Vitamins A, C, and E.

Reduced glutathione in intestinal lumen.

5

Inhibitors

Heavy metals, especially Mercury.

Phytic acid (via chelation and precipitation).

6

Selenoprotein P

Forms in the liver from organic and inorganic forms of selenium.

Antioxidant and transporter.

Contains most of the body's selenium 50-80% plasma

3 hour half life

7

Glutathione peroxidase

Selenoprotein

Antioxidant
Protects against lipid radicals (peroxide & hydrogen-peroxide)

Spares vitamin E

Assess Se status

Transports 10-30% of Se in plasma

8

Where is selenium stored?

Thyroid gland
Kidneys
Liver
Heart
Muscle

9

Selenocysteine

Dietary selenocysteine cannot be used by the body.

Organic. "21st" AA. Needed for Se-dependent proteins. Has its own tRNA.

Catabolized into (inorganic) selenide.
Either methylated to be excreted via urine. Or converted back to selenocysteine (endogenous).

10

Selenomethionine

Enters AA pool. Used for protein synthesis.
Catabolized to make selenocysteine.

Best absorbed form of all selenoproteins.

AA transporters.

Organic.

11

Transport

Selenoamino acid are transported across basolateral membrane via AA transporters.

No one knows how inorganic selenium is transported.

12

Mercury binding

When selenium binds to mercury, it prevents mercury from being absorbed.

Mercury can replace selenium which means selenoproteins cannot develop. Mercury poisoning.

13

Inorganic Selenium

Selenite
Selenate
Selenide
Go directly to selenium pool and readily available.

Not incorporated into AA.

Pills, animal feed, cabbage, beets, yeast.

14

Supplements

Either selenocysteine or an inorganic selenium is optimal.

Inorganic is directly available for use.

Selenomethionine is stored in tissues and not readily used.

15

Pathway

1. Selenocysteine.
2. Selenide.
3. Selenoproteins.
4. Endogenous Selenocysteine.
5. Selenium dependent proteins produced.

16

Hexomonophosphate shunt

Reduces glutathione using niacin

17

Thioredoxin reductase

Helps reduce vitamin C and recycle it.

18

Iodothyronine 5' deiodinases

Helps remove iodine
Activates thyroid hormone to prevent goiter

19

Antioxidant nutrient interactions

Se increases vit C
Vit C recycles vit E
Se spares vit E