FINAL: selenium

Question 1

bioactive form of selenium

Answer 1

selenoproteins

Question 2

2 selenoamino acids present in proteins

Answer 2

1. selenomethionine (plants)
2. selenocytsteine (animals)

Question 3

what do selenoamino acids make

Answer 3

selenoproteins

Question 4

Se RDA increases with

Answer 4

age
pregnancy
lactation

Question 5

Se food source

Answer 5

brazil nuts
fish
meat

Question 6

can Se lead to toxicity

Answer 6

YES
only Se and vit A

Question 7

levels of Se in men and women are same but,

Answer 7

women consume less, so they must have better control

Question 8

Se toxicity inhibits

Answer 8

protein synthesis

Question 9

__% absorption of Se in gut

Answer 9

80-98% absorption of Se in gut

Question 10

selenium absorber

Answer 10

SLC26

Question 11

Se absorption in gut

Answer 11

1. selenate and selenite enter SLC26
2. Se-cysteine (animals) and Se-methionine (plants) enter B0AT and rBAT
3. some to functional pool, rest to portal circulation

Question 12

B(0)AT is dependent on

Answer 12

Na

Question 13

__ uptakes 50% Se

Answer 13

liver uptakes 50% Se

Question 14

most Se in post-hepatic circulation is transported by __

Answer 14

most Se in post-hepatic circulation is transported by selenoprotein P

Question 15

selenoprotein P is made in __ and secreted into __

Answer 15

selenoprotein P is made in liver and secreted into circulation

Question 16

elemental selenium in body is called

Answer 16

selenide

Question 17

what is the main transporter of selenium in circulation

Answer 17

selenoprotein P

Question 18

SEC =

Answer 18

selenocysteine

Question 19

selenide can be converted to __ by __

Answer 19

selenide can be converted to selenophosphate by selenophosphate synthetase

Question 20

All selenium we consume is converted to

Answer 20

selenide

Question 21

selenide pathway

Answer 21

1. selenide to selenophosphate
2. selenophosphate uses tRNA for Serine to become selenocysteine
3. selenocystine is used in translation and protein synthesis

Question 22

selenoprotein synthesis trxn

Answer 22

UGA (normally a stop codon) codes for seleno-cysteine when SECIS is present

Question 23

what must be present for UGA to not be read as a stop codon

Answer 23

SECIS

Question 24

high selenium is found in what organs and why

Answer 24

1. thyroid bc thyroid hormones
2. liver bc 1) it directs Se to where it needs to go and 2) liver has DI1 which makes T3

Question 25

Se homeostasis is controlled by

Answer 25

kidney

Question 26

se excretion

Answer 26

50-60% urinary (as selenosugar) 40-50% feces

Question 27

with high intake __ are secreted in urine as well as selenosugars

Answer 27

with high intake **di and tri-methyl metabolites** are secreted in urine as well as selenosugars

Question 28

3 functions of Se

Answer 28

1. defense against oxidative stress (glutathione peroxidase) 2. regulate thyroid hormones (5'-DI) 3. regulate redox status (thioredoxin reductases)

Question 29

glutathione peroxidase functions (2)

Answer 29

1. destroys free radicals 2. prevent oxidative damage produced by peroxidases

Question 30

4 types of glutathione peroxidases

Answer 30

GPX1: cells and plasma GPX2: GI cells GPX3: Se transport (milk, plasma) --> kidney GPX4: IC lipid peroxidase

Question 31

which GPX is most important

Answer 31

GPX4 bc it prevents membrane damage

Question 32

5-deiodinases function

Answer 32

activate and inactivate thyroid hormones

Question 33

different DIs

Answer 33

DI1: liver, produces circulating T3 DI2: brain, pituitary, IC production of T3 DI3: brain, fetus, inactivates T3

Question 34

thioredoxin reductases function

Answer 34

regulates IC redox state synthesis of deoxynucleotides (DNA synthesis)

Question 35

major plasma and EC selenoprotein

Answer 35

selenoprotein P

Question 36

selenoprotein P 2 roles

Answer 36

Se transport antioxidant

Question 37

assessing Se

Answer 37

1. enzyme activities (GPX3, GPX1, Selenoprotein P) 2. GPX activity in RBC (long-term) 3. Se levels (variable)

Question 38

Se deficiency associated with

Answer 38

1. cancer 2. cognitive decline 3. thyroid disease 4. CVD

Question 39

when to supplement Se

Answer 39

only in deficient individuals (not in ppl with normal levels)

Question 40

Keshan disease

Answer 40

chronic Se deficiency children and adolescents in China focal myocardial necrosis heart insufficiency heart enlargement and dysrhythmia pulmonary edema