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NUTR2101 > Week 12 > Flashcards

Week 12 Flashcards

1
Q

What are the two forms of iron in the body?

A

Heme iron (ferrous iron): Fe2 +, for absorption

Non-heme iron (ferric iron): Fe3 +, for transport

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2
Q

How and where is iron absorbed in the body?

A

In small intestine, mediated by carrier proteins

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3
Q

What converts Fe3+ to Fe2+?

A

Ferrireductase in the brush-border

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4
Q

What are the two carrier proteins for iron and what are their functions?

A

Ferritin: binds and stores iron in enterocytes (and other tissues)

Ferroportin: transports iron out of enterocytes when supplies are low for release into the blood

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5
Q

What are the ferroxidase enzyme used to convert Fe2+ to Fe3+

A

hephaestin in enterocytes

ceruloplasmin in the blood

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6
Q

How is iron transported?

A

As Fe3+

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7
Q

Where and how is iron stored?

A

In the liver, bone marrow, spleen, bound to ferritin or hemosiderin

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8
Q

What are the functions of iron

A
  1. Hemoglobin: Transport of oxygen and carbon dioxide
  2. Myoglobin: transport of oxygen
  3. Oxidation reduction reactions
  4. Immune system function
  5. Energy metabolism
  6. Alcohol and drug metabolism
  7. Cofactor in enzymes involved in making neurotransmitters
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9
Q

Where is iodine absorbed?

A

Small intestines

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10
Q

what decreases the absorption of iodine?

A

Goitrogens foods decrease iodine availability for absorption

Turnips, cabbage, brussels sprouts, broccoli, potatoes, cassava, peanuts, soy, peaches, strawberries

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11
Q

how is iodine transported?

A

Bound to thyroglobulin, taken to the thyroid gland

Sodium-dependent transport system traps iodine in thyroid gland for hormone synthesis

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12
Q

Where is iodine stored?

A

muscle, thryiod gland, skin

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13
Q

What are the two forms of iodine and what do they function as?

A

T4 is the form of thyroid hormone in the circulation

T3 is the active hormone form

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14
Q

A Goiter and cretinism is the result of what deficiency?

A

Iodine

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15
Q

How is the absorption of zinc increased?

A 
consumed in small amounts 
zinc defiency (increase need) 
certain amino acids 
presence of riboflavin
yeast in leavened bread increases absorption x 10 by cleaving phytates from Zn
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16
Q

What impairs the absorption of zinc?

A 
polyphenols, high fiber due to phytates
alcohol 
phytic acid and fiber in whole grains 
excessive zinc intake 
high non heme iron intake 
good zinc status
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17
Q

When absorbed: zinc promotes the synthesis of what?

A

metallothionein in enterocytes to bind zinc and keep it in there for controlled release

18
Q

What is Metallothionein?

A

a binding protein (similar to ferritin) that blocks zinc’s movement into bloodstream (prevents excess absorption into the bloodstream)

19
Q

What does zinc deficiency lead to?

A

Anorexia
Leads to: delayed growth, poor development in children
Dermatitis, impaired vitamin A, D and thyroid hormone function, alopecia, poor wound healing
Decreased taste and immune function

20
Q

where how is copper absorbed?

A

small instestion

diffusion and active transport

21
Q

What decreases copper absorption?

A

large intake of Cu, Fe and Zn, phytates

22
Q

How is copper transported in the body?

A

Bound to protein, e.g. albumin, taken to the liver -

Released to other tissues from the liver bound to ceruloplasmin

23
Q

Where is copper stored?

A

iver and kidney

24
Q

What can copper difficiency result from?

A

Menke’s disease: genetic disorder interfering with copper transport and adequate delivery to tissues

25
Q

What does toxicity lead to?

A

Wilson’s disease: genetic disorder where too much copper builds up in tissues rather than being excreted

26
Q

where and how is manganese absorbed?

A

Small intestine via diffusion and active transport

27
Q

How is manganese transported?

A

Taken to the liver bound to alpha-2 macroglobulin

From liver transported to pancreas, kidney, bone bound to
transferrin and alpha-2 macroglobulin

28
Q

Functions of manganese

A
  1. Cofactor in enzymes involved in:
    • Carbohydrate metabolism
    • Gluconeogenesis
    • Antioxidant defense
  2. Cholesterol synthesis
  3. Nitrogen metabolism: urea synthesis
  4. Cofactor to enzymes in the synthesis of proteoglycans required in formation of cartilage and bone
  5. Cofactor in wound healing processes
29
Q

What happens in manganese deficiency?

A

Poor growth, skeletal abnormality, impaired glucose metabolism, abnormal reproductive function

Bone resorption occurs to provide Mn

30
Q

What happens in manganese toxicity?

A

Severe neurological impairment (manganism), muscle stiffness, tremors, Parkinson’s like symptoms

31
Q

What is bound to selenium when it is absorbed?

A

methionine (selenomethionine) and cysteine (selenocysteine)

32
Q

What interfers with selenium absorption?

A

Phytates and presence of heavy metal (mercury)

33
Q

What enhances selenium absorption

A

Presence of vitamins A, C and E

34
Q

What is the biologically active form of selenium?

A

Selenocysteine

35
Q

Functions of selenium

A

Component of 25 enzymes and proteins

Is part of the antioxidant defense system as cofactor of: glutathione peroxidase. Helps prevent lipid peroxidation; spares vitamin E activity for other antioxidant functions

Thyroid metabolism: conversion of T4 to T3 as cofactor of iodothyronine deiodinase

36
Q

What is selenium toxicity called?

A

Selenosis

37
Q

When is chromium absorption increased

A

low intake and when vitamin C is present

38
Q

What are the functions of molybdenum?

A

Purine metabolism: xanthineoxydase breaks down nucleotide to form uric acid (also part of endogenous antioxidant capacity)

Conversion of sulfite to sulfate required in metabolism of sulphur containing amino acids: sulfite oxidase

Metabolism of medications (drugs) and toxins: aldehyde oxidase

39
Q

How is fluoride absorbed in the body?

A

rapidly from the stomach and small intestine by passive diffusion

40
Q

What are the functions of fluoride?

A

Promotes bone and dental health in childhood and adulthood:
- Deposition of calcium and phosphorous
- Preventing caries: hydroxyfluoroapatite crystals deposit
- Resistance to bacteria that convert CHO in mouth to organic acids that dissolve tooth enamel
- In the saliva:
- Helps remineralisation of enamel damage - Reduces loss of minerals from enamel
- Increase of spinal bone mass at pharmacological
dose.

41
Q

what does a fluoride defiency cause?

A

dental caries

42
Q

What does fluoride toxicity cause?

A

Mottling and fluorosis of tooth enamel, pitting of enamel

Gastric irritation and joint pain

NUTR2101 (14 decks)

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