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HUN 4221 EXAM 3 > Selenium > Flashcards

Selenium Flashcards

1
Q

Selenium shares chemical properties with what element?

A

Sulfur

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2
Q

How much selenium is needed

A

55 MICROgrams

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3
Q

What foods are high in Se?

A

Brazil nuts,

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4
Q

Why are brazil nuts high in Se?

A

It depends on the Se concentrations in soil

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5
Q

What are the Plan food forms of Se?

A

Selenomethionine and selenocysteine

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6
Q

What are the animal food forms of Se?

A

Selenocysteine

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7
Q

How are Organic forms of Se absorbed in the intestine?

A

Like AA via AA transporters

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8
Q

How are inorganic forms of Se absorbed?

A

Not known

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9
Q

Are selenomethionine and selenocysteine transported differently?

A

No

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10
Q

In Se deficiency what happens to absorption?

A

Nothing. Rate stays the same.

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11
Q

What is another name for Selenocytsteine?

A

The 21st Amino acid

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12
Q

Selenocysteine (Sec) occurs in how many proteins in the human proteome?

A

25 proteins

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13
Q

Conventional cysteine can do what that Sec can do?

A

fulfills a chemical function

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14
Q

What makes Sec different from other AA?

A

It is not coded for directly in the genetic code. It relies on independent SEC insertion machinery

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15
Q

What does SECIS stand for?

A

SelenoCysteine insertion sequence

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16
Q

What is SECIS?

A

A stemloop structure in the mRNA

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17
Q

How is sec put into proteins?

A

When an mRNA codes for UGA, the SECIS element binds to a SECIS binding protein which binds to elongation factors which is bound to a tRNA which will bring Sec in for UGA and keep moving.

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18
Q

The functions of the selenoproteins that we do know function in what?

A

antioxidant and anabolic processes

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19
Q

What is Selenoprotein P (SELP)?

A

Major Se transport protein

Accounts for 80% of plasma Se

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20
Q

Where SELP produced?

A

Liver

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21
Q

How many Se can SELP hold?

A

10 atoms/ molecule

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22
Q

What is a side function of SELP?

A

As an antioxidant for peroxynitrite radicals

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23
Q

What happens if you KO SELP?

A

Mice have neurological problems and trouble walking

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24
Q

What was the first selenoprotein identified in 1957?

A

Glutathione Peroxidase 1

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25
Q

Gluthione peroxidase 1 accounts for how much of total body Se?

A

more than 50%

26
Q

What is glutathione peroxidase 1?

A

An antioxidant enzyme

27
Q

What is Glutathione peroxidase 1 side function?

A

Function as a Se buffer

28
Q

How does Glutathione peroxidase function as an antioxidant enzyme?

A

It converts hydrogen peroxide to water

29
Q

Which GPx proteins work to detoxify H2O2?

A

GPx1 (cytosol), GPx2 (cytosol), GPx3 (plasma), GPx6 (cytosol).

30
Q

What does GPx4 function as?

A

protects lipids from H2O2 mediated oxidation

31
Q

What is thioredoxin reductase?

A

Enzyme that reduces thioredoxin

32
Q

How does thioredoxin protein act as an antioxidant?

A

By acting as an electron donor (reducing agent)

33
Q

What does thiredoxin reductase regenerate?

A

Thioredoxin

34
Q

What is SelenoproteinW? (SELW)

A

Small selenoprotein found in muscle (implicated in white muscle disease that affects sheep)

35
Q

How do you prevent white muscle disease?

A

Supplement soil with Se

36
Q

How much Se can the body store?

A

30 mg

37
Q

What tissue has the greatest concentration of Se?

A

The kidney

38
Q

What tissue has the most Se?

A

Muscle

39
Q

What form of excretion is important for maintaining homeostasis?

A

Urinary excretion

40
Q

Pharmacologic doses of Se are released how?

A

Expired in the breath as diemthylselenide

41
Q

What is the major form of Se in the urine?

A

Methylselenol

42
Q

Se def rat

A

Visually smaller, leg weakness, rough hair coat, display muscle degeneration, reporoductive failure and liver necrosis if also Vit. E def

43
Q

Se has been shown to correct what?

A

Liver necrosis cause by a lack of methionine, cysteine, or vitamin E

44
Q

Human Se def was first reported where?

A

In China

45
Q

What is Keshan Disease?

A

Human Se Def

Causes cardiomyopathy

46
Q

What causes Keshan disease?

A

Low levels of Se in certain area and viral infection

47
Q

What is Kashin-Beck disease?

A

Human Se def
Endemic disease of the cartilage
Due to low Se in soil (affects people in northern china and russia) and iodine def or toxic contamination may be involved.

48
Q

Does Se supps cure Kashin-beck?

A

No.

49
Q

What is Myxdematous Cretinism?

A

Disease characterized by thyroid enlargement and decreased intelligence

50
Q

What contributes to Myxedematous cretinism?

A

Se and Iodine deficiency

51
Q

Se status assessment

A

Intake indicators

  • plasma/serum selenium: reflects recent diet
  • red blood cell selenium: past 120 days
52
Q

Where was Se toxicity first identified?

A

In livestock0 they consumed plants grown in high-se soil

53
Q

Why are inorganic Se and amino acid forms toxic in excess?

A

Because they are highly bioavailable

54
Q

What is Selenosis?

A

Chronic Se toxicity

55
Q

What is commonly associated with selenosis?

A

Changes in nail structure, loss of nails, and hair

56
Q

Continued ingestion of Se during Selenosis leads to:

A
  • lesions of the skin and nervous system
  • nausea
  • weakness
  • diarrhea
57
Q

Symptoms of selenosis are present with what intake range?

A

3.2-6.7 mg /day

58
Q

What causes acute Se toxicity?

A

Caused by ingestion of gram quantities of Se

59
Q

What does acute Se toxicity cause?

A

GI and neurological disturbances
MI (Myocardial infarction)
Renal failure
Acute respiratory distress syndrome

60
Q

How do you fix Se overdose?

A

There is no cure, it is fatal

61
Q

What is Se strange? (LONG NOTECARD)

A
  • Se is taken up form soil by the plants and incorporated into Sec. Neither Se or Sec are required for plants.
  • Se takes the place of another atom (S) in cysteine and forming a new AA (Sec)
  • Sec is not encoded for in the genomes; SECIS element is used
  • Se absorption does not increase in deficiency
  • Se def and toxicity are due to inadequate/excessive intake (which are directly caused by [Se] in soil)

HUN 4221 EXAM 3 (9 decks)

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