Selenium Flashcards
(100 cards)
Selenium is an…
Essential trace element
Primary function of Se
Incorporation into selenoproteins (25)
Inorganic selenium is found in…
Soil
Selenite
SeO32
(Inorganic)
Selenous acid
H2SeO3
(Inorganic)
Selenate
SeO42
(Inorganic)
Organic selenium is found in…
Plants & animals
Describe formation of organoselenium compounds (i.e. SeCys, SeMet)
Plants/microorganisms replace sulfur with selenium in the biosynthetic pathways for cysteine and methionine (sulfur-containing amino acids)
Selenoamino acids are defined as…
Se covalently bonded with carbon atoms (i.e. SeMet, SeCys)
Selenomethionine (SeMet) synthesis
Synthesized by plants/microorganisms
Selenocysteine (SeCys) synthesis?
Co-translationally synthesized in animals/humans
Inorganic selenide is activated and added in a co-translational conversion of serene –> SeCys while the AA is bound to a specific tRNA coding for the selenoprotein
Methionine =
Essential amino acid in humans/animals (diet only)
Cysteine =
Synthesized from methionine
Selenium RDA is…
Adults: 55 mcg/day
Infants: 15 mcg/day up to 20 mcg/day after 6 mos (based on breast milk)
Children: 20-40 mcg/day
Pregnancy: 60 mcg/day Lactation: 70 mcg/day
Selenium intakes of most Americans exceed the RDA
Selenium RDA mostly based on…
Maximal expression of glutathione peroxidase 3
What determines selenium content of plant-based foods?
Varies according to soil Se levels, which are affected by:
Soil pH
Organic matter in dirt
Form of selenium present
Se content of foods tends to correlate with…
Protein content; because SeCys and SeMet are mostly incorporated into proteins
Muscle meats contain…
0.3 to 0.5 mg Se/kg (fresh weight)
Organ meats contain __x higher/lower concentrations of Se
4x to 15x higher
Foods high in selenium
Brazil nuts, fish, organ meats, muscle meats, high protein foods
Absorption of inorganic Se from food is __% (selenite)
84%
Absorption of organic Se from food is __% for SeMet
98%
Inorganic Se (selenate/selenite) absorbed via…
Diffusion
Selenoaminoacids absorbed via…
Transport by amino acid transporters



