Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

HUNT241 > Nutrition Lecture 4: Selenium > Flashcards

Nutrition Lecture 4: Selenium Flashcards

1
Q

What is selenium?

A

An essential trace element

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How does selenium intake range globally?

A

Large geographical intakes from deficiency to toxicity - China’s intake is extremely high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the RDI for selenium?

A

Women = 60ug/day
Men = 70ug/day

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the different species of selenium?

A

Organic and Inorganic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the two organic forms of selenium?

A

SeCys and SeMet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What form of selenium is found in animal products?

A

SeCys

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What form of selenium is found in plant products?

A

SeMet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the two inorganic forms of selenium?

A

Selenate (SeO2- 4)
Selenide (SeO2- 3)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the active part of selenium?

A

SeCys - responsible for 99% of the metabolic actions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are inorganic forms of selenium not attached to?

A

Not attached to amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How does Se enter the food chain?

A

Through plants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the Se content of plants affected by?

A

Availability of Se in soil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What matter in soil absorbs Se?

A

Organic matter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What binds Se?

A

Clay minerals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What form of Se do alkaline soils favour?

A

Selenate - more bioavailable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What form of Se fo acidic-neutral soils favour?

A

Selenide - less bioavailable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the three classifications of Se accumulation in plants?

A
  1. Hyperaccumulators
  2. Secondary-accumulators
  3. Non-accumulators
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are hyperaccumulators?

A

Accumulate >1000mg/Se/kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is an example of a hyperaccumulator plant?

A

Brazil nuts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are secondary-accumulators?

A

Accumulate up to 100-1000mg/Se/kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are examples of secondary-accumulators?

A

Brassica (rapeseed, broccoli, cabbage) Allium (garlic, onions, leeks)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are non accumulators?

A

Accumulate <100mg/Se/kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are examples of non-accumulators?

A

Wheat crops (wheat, oats, barley, rye) Rice

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Is NZ considered a deficient, low or rich region of Se?

A

Low region - we have moderate to low intakes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are good food sources of Se?

A

Brazil nuts, Seafood, kidney, livers and brains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What food sources do NZ’ers get their Se from?

A

Bread, seafood, chicken

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are the regional differences in Se intake in NZ?

A

Intake is significantly higher in the North Island

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Why are animal sources of Se more reliable than plant sources?

A

Plant sources are affected by soil variability, whereas animals have an absolute requirement for Se - If the soil is deficient in selenium, the animals must be fed it from somewhere else

29
Q

What is the absorption of Se?

A

High - 80% from food sources

30
Q

Where is selenium processed?

A

In enterocytes

31
Q

What is organic selenium converted into?

A

Into H2Se and then packaged into lipoproteins

32
Q

After selenium is packaged into lipoproteins where does it go?

A

Taken into the liver and converted into a functional protein - selenoprotein

33
Q

What does organic Se need to be converted into before it can be used in the body?

A

Selenoprotein

34
Q

What are inhibitors of Se absorption?

A

None are known

35
Q

How many classes of selenoproteins are there?

A

25 known classes

36
Q

What are the biological processes of selenoproteins?

A
  • Antioxidant defence
  • Inflammation
  • Muscle development
  • Reproduction
  • Thyroid hormone metabolism
  • Immune function
37
Q

What is selenocysteine?

A

The active part of a selenoprotein - an essential amino acid component in selenoproteins

38
Q

Is selenoprotein synthesis regulated?

A

Highly regulated - there is a maximum amount of selenoproteins that we can and will synthesise

39
Q

How do differences arise in selenoprotein function and usage between people?

A

Within the 3UTR you can sometimes get differences in polymorphisms which affects the function of the protein

40
Q

What are glutathione peroxidases (GPx)

A

selenium-containing antioxidant enzymes

41
Q

What are the different forms of GPx?

A

GPx1
GPx3
GPx4

42
Q

Where is GPx1 found?

A

in the cytosol of cells

43
Q

Where is GPx3 found?

A

is extracellular in the blood and plasma, and ECF

44
Q

Where is GPx4 found?

A

in phospholipids

45
Q

What is the main function of GPx?

A

Antioxidant defences

46
Q

What 2 main antioxidant defences does GPx carry out?

A
  • Reduces hydrogen peroxide and other organic hydroperoxides
  • Protects tissues from inflammatory and oxidative damage
47
Q

What are thioredoxin reductases?

A

Selenium containing enzymes

48
Q

What is the function of Thioredoxin reductases?

A

involved in vital cell processes, found everywhere

49
Q

What does liver disease reduce?

A

reduces selenoproteins

50
Q

What does kidney disease reduce?

A

GPx3

51
Q

What type of stress upregulates selenoprotein synthesis?

A

Oxidative stress

52
Q

What does inflammation reduce?

A

Plasma Se is reduced during acute phase

53
Q

What are selenium-containing proteins?

A

Differ from selenoproteins, proteins in the body that incorperate seleno-methionine

54
Q

What does SeMet stand for?

A

Seleno-methionine

55
Q

What happens when Se availability is limited?

A

Incorporation of Se into individual selenoproteins is prioritised

56
Q

What selenoprotein is at the top of the hierarchy (activities maintained when deficient)?

A

GPx4

57
Q

What selenoprotein is at the bottom of the hierarchy (activities drop when deficient)?

A

GPx1

58
Q

What body tissues does Se prioritise when deficient?

A

Brain, endocrinological, reproductive tissues

59
Q

What body tissues does Se disregard when deficient?

A

Heart, liver, kidney, lung tissues

60
Q

What body parts can Se concentration be measured in? (long term intake)

A

Urine, toenails, hair

61
Q

How is Se commonly measured? (short-medium term intake)

A

Plasma/serum Se concentration (SelP and GPx3)

62
Q

What plasma selenoprotein reflects liver concentration?

A

SelP

63
Q

What plasma selenoprotein reflects kidney concentration?

A

GPx3

64
Q

What is the relationship between plasma Se and dietary intake?

A

Plasma Se concentrations increase with increasing Se intake

65
Q

When do we see a sharper increase in plasma Se?

A

When Se intakes are less than 70ug/day

66
Q

When do plasma Se concentrations decrease?

A

During acute phase (inflammation/sickness)

67
Q

When does plasma GPx activity reach maximum? (plateus)

A

at Se intakes of 40-60ug/day (plasma Se of 85ug/L)

68
Q

When does plasma SelP concentration reach maximum? (plateus)

A

at Se intakes of 95ug/day (plasma Se of 120ug/day

69
Q

What is the relationship between selenium and all-cause mortality?

A

Risk of all cause mortality is highest risk at low and high concentrations - want to sit at recommended (U shape relationship)

HUNT241 (22 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions