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Nutrition and Metabolism > Micronutrition Metabolism > Flashcards

Micronutrition Metabolism Flashcards

1
Q

What are minerals?

A

inorganic elements that have physiological function within the body

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2
Q

What does it mean to say “essential” (mineral)?

A

must be supplied in diet (food/fluids) and vary in amounts

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3
Q

How much of the total body weight do minerals constitute %?

A

4%

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4
Q

What are the potential roles of the minerals, with its constraints?

A
  • difficult in assessing status, thereby, defining requirements
    myriad interactions among minerals and other nutrient and non-nutrients in diet
  • sometimes, natural experiments of genetic disorders can thrown light on potential roles of minerals in disease processes
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5
Q

Dietary sources of Calcium:

A
  • milk/milk products
  • cereal/cereal products
  • fish
  • tofu
  • green vege, dried fruit
  • nuts, pulses
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6
Q

What is the % of calcium in human body weight?

A

1-2%

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7
Q

What is the % calcium in body’s mineral mass?

A

40%

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8
Q

What is the kg of calcium in human body weight?

A

1 kg

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9
Q

How much calcium % is in bones and teeth?

A

99%

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10
Q

how much calcium % is in extracellular fluid, blood, muscle and other tissues?

A

1%

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11
Q

What formed must calcium be in for it to be absorbed?

A

ionized

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12
Q

What two routes are calcium absorbed in intestines?

A
  1. Paracellular: passive calcium transport through tight junctions between mucosal cells
  2. Transcellular route: involve active transport by mucosal calcium transport protein
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13
Q

What is the mucosal transport protein called?

A

calbindin

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14
Q

What is calbindin like?

A
  • saturable

- subject to physiological and nutritional regulation via vit. D

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15
Q

Is the paracellular route dependent on anything? Explain

A

Yes, dependable on concentration

But, No. It’s nonsaturable, independent of nutritional/physiological regulation,

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16
Q

Explain the process of calcium digestion, absorption and transport:

A
  1. Ca2+ cross bursh border membrane of enterocyte through calcium channel TRPV6
  2. Ca2+ binds to calbindin D which carries calcium across cytosol of enterocyte
  3. Ca2+ -ATPase pumps calcium across basolateral membrane for entrance into blood
  4. Some Ca2+ is absorbed between cells, typically with high luminal Ca2+ concentrations
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17
Q

In a mixed diet, how much % calcium is absorbed?

A

10-30%

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18
Q

What are examples of calcitropic hormones, and at what levels of calcium are they triggered?

A
  • parathyroid hormone (PTH) = low calcium
  • 1,25(OH)2D3 = low calcium
  • calcitonin = high calcium
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19
Q

What are the functions of calcium?

A
  • only nutrient whose storage form serves functional role = bone
  • muscle/nerve stimulation
  • blood clotting, wound healing
  • hormones
  • growth and metabolism
  • prevention of osteoporosis, hypertension and protection against colon cancer
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20
Q

What is the bone made of in %?

A

60-70% mineral

30-40% water and protein

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21
Q

What is the structure of bone?

A

crystalline structure of Ca + phosphate, laid down on organic matrix of collagen

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22
Q

What are the two types of bones and the % of it?

A
  • cortical bone (75%)

- trabecular bone (25%)

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23
Q

Which type of bone has a fast turnover rate? (t/o)

A

trabecular bone

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24
Q

What regulates bone metabolism?

A

osteoblast and osteoclast

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25
Q

How much % of adult skeleton is replaced each year?

A

10%

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26
Q

What are osteoblasts?

A
  • bone forming cells
  • secrete collagen and form matrix
  • become calcified
  • form osteocytes
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27
Q

What are osteoclasts?

A
  • resorb bone by dissolving Ca and phosphate

- release minerals to circulation

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28
Q

What is the purpose of bone remodelling?

A
  • prevent accumulation of damaged/fatigued bone by regeneration
  • allow bone to respond to changes in mechanical forces
  • facilitate mineral homeostasis and turnover
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29
Q

What is peak bone mass and when does it occur?

A

20-30yo

  • 90-95% achieved during growing years
  • declines after 30
  • greater in males and afro-caribbeans
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30
Q

What is the rate of calcium accumulation in skeleton?

A

150mg/day

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31
Q

What are some calcium metabolic functions?

A
  • promotes blood clotting
  • involved in muscle contraction (calmodulin)
  • involved in cellular reactions (cellular second messenger of hormonal action)
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32
Q

What is the recommended intake of calcium for pregnant women?

A

700mg/day

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33
Q

What is the recommended safe upper limit of calcium in adults?

A

2500mg/day

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34
Q

What is the recommended lower limit LRNI of calcium in adults?

A

400mg/day

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35
Q

What two things can possibility inhibit absorption of calcium?

A

phytates and fibre

36
Q

How much phosphorus is in the body in % and g?

A

0.65-1.2%

600g

37
Q

How much phosphorus % is in bone?

A

85%

38
Q

How much phosphorus is in soft tissues?

A

15%

39
Q

What are sources of phosphorus?

A
  • cheese/cheddar
  • yoghurt
  • lentils
  • milk
  • chicken, roasted
  • ground beef
  • soy milk, peanut butter
40
Q

What form is phosphorus usually found in?

A
  • combination with minerals

- commonly in pentavalent form in combination with oxygen (PO4^(3-))

41
Q

What is the value of plasma phosphorus?

A

3.5mg/100ml

42
Q

Name 7 phosphorus-containing compounds in the body?

A
  1. DNA
  2. RNA
  3. ATP
  4. Creatine phosphate
  5. c-AMP
  6. Inositol 3-phosphate
  7. Phospholipids
43
Q

What are the functions of phosphorus?

A
  • bone mineralisation
  • phospholipids (major mem. component)
  • activation of molecules
  • nucleotide/nucleoside phosphates
  • acid-base balance
  • temporary storage and transfer of energy derived from metabolic fuels
44
Q

What specifically are the functions of phosphates as nucleotides/nucleosides?

A
  • structural role
  • energy storage and transfer
  • intracellular second messenger
45
Q

But what are the (actual) functions of phosphorus?

A
  • support tissue growth (individual development OR through pregnancy/lactation)
  • replace excretory and dermal levels
46
Q

What are possible sources of magnesium?

A
  • almonds, cashews, peanuts
  • spinach
  • shredded wheat cereals
  • soymilk
  • black beans, edemame
  • peanut butter, bread, etc
47
Q

How is magnesium homeostasis maintained?

A

by controlling efficiency of intestinal absorption and magnesium losses through the urine

48
Q

What is the % absorption of Mg in small intestines?

A

20-70%

49
Q

What are the 3 mechanisms Mg crosses intestinal epithelium?

A
  • passive diffusion
  • solvent drag (following water movement)
  • active transport
50
Q

What are the functions of Mg?

A
  • neuromuscular activity transmission
  • cardiac muscle contraction
  • cellular (second messenger) role
51
Q

What specifically are the functions of Mg in cellular role?

A
  • activates enzymes for CHO and protein metabolism
  • transportation of Na and K across cell membranes
  • influences utilisation of K, Ca and protein
  • Mg deficits are frequently accompanied by K and/or calcium deficit
52
Q

Salt is widely used for?

A
  • modifying flavour
  • alter texture/consistency of food
  • control microbial growth
53
Q

Where is chloride mainly found?

A

ECF, and fully water soluble as chloride anion

54
Q

What enhances the uptake of sodium?

A

glucose and anions (citrate, propionates and bicarbonate enhance the uptake of sodium)

55
Q

In a 70kg male, how much sodium is in his body?

A

90g

56
Q

In a 70kg how much % sodium contained in mineral apatite of bone?

A

75%

57
Q

What conserves sodium and increases the Na reabsorption in kidney?

A

angiotensin and aldosterone

58
Q

What happens in Na depletion?

A
  • stimulate renal production of renin (generates active angiotensin in circulation)
  • stimulates vasoconstriction
  • increase blood pressure
  • decrease water loss
  • stimulates aldosterone release from adrenal cortex
59
Q

What does the atrial natriuretic hormone do?

A
  • counteracts the Na retention mechanisms by suppressing renin and aldosterone release - by inducing water/Na excretion
  • decreases bp and antagonize angiotensin
60
Q

What would be stimulated as a result of raised plasma sodium concentration?

A
  • renal reabsorption of water

- decreases urinary output via antidiuretic hormone from posterior pituitary

61
Q

This is in contrast to sodium, but how is chloride distributed?

A
  • passively distributed throughout the body

- moves to replace anions lost

62
Q

How much iron is in the body?

A

2-4g

63
Q

What are dietary sources of iron?

A
  • red meat, liver (haem form)
  • dark green, leafy vegetables
  • fortified breakfast cereals
64
Q

Describe haemoglobin:

A
  • Fe centrally located in Hb molecule
  • porphyrin ring
  • red blood cells
65
Q

Functions of haemoglobin:

A
  • Hb transports oxygen in red blood cells
  • necessary for all aerobic cells and tissue
  • vital for all aerobic physical activity
66
Q

Where are the iron stores?

A
  • stored as ferritin and haemosiderin

- in liver, bone marrow and spleen

67
Q

What is the DRV (dietary reference values) for iron in men and women?

A 
men = 8.7mg/d
women = 14.8mg/d
68
Q

What are the terms to describe toxicity in iron?

A 
haemochromatosis = Fe overload + tissue damage
haemosiderosis = Fe overload w/out tissue damage
69
Q

How much zinc in g is in the human body?

A

1.5-3.0g

70
Q

Where is it found?

A

all organs, tissues and body fluid

71
Q

What are some sources of zinc?

A
  • oysters
  • chicken
  • cheddar cheese
  • cashew, watermelon seeds, almond
  • milk, yoghurt
  • red meat, salmon
  • cocoa
72
Q

What are some functions of zinc?

A
  • metalloenzyme component
  • gene expression: zinc fingers
  • membrane/cytoskeletal stabilisation
  • immune function
  • sexual maturation
  • fertility and reproduction
73
Q

What are zinc fingers?

A

proteins with secondary structure of shape, due to presence of zinc atom linked through cysteinyl or histidyl residues in protein

74
Q

Where are zinc fingers found?

A

within transcription factors that bind to metal response/regulatory elements in promoter regions of genes to enhance/inhibit transcription

75
Q

What is the recommended intake of iodine in adults?

A

150mcg/d

76
Q

What is the recommended intake of iodine for pregnant/breastfeeding women?

A

250mcg/d

77
Q

What is the main result of excessive iodine intake?

A

thyroid problems

78
Q

What is the maximum intake of iodine?

A

600mcg/d

79
Q

What are the sources of iodine?

A
  • cow’s milk
  • sea fish and shell fish
  • seaweed
80
Q

What are iodine’s metabolic functions?

A
  • forms thyroid hormones (T3 and T4)
  • regulates BMR and cellular metabolism
  • needed for nervous system development in foetus, and pregnancy
81
Q

What are the physiological effects of thyroid hormones?

A
  • enhance lipolysis in adipose tissue
  • enhance contraction in muscle
  • promote anabolism in bone
  • increase heart rate
  • stimulate nutrient digestion and absorption
  • stimulate metabolic rate and cellular oxygen consumption in metabolically active tissues
82
Q

What are the functions of Manganese?

A
  • urea formation

- antioxidant enzymes

83
Q

What are the sources of Mn?

A
  • tea, nuts, cereals
84
Q

Deficiency of Mn:

A

interferes with absorption

85
Q

What happens in toxicity of Mn?

A
  • hallucinations, memory or motor coordination affected

- Parkinson’s like symptoms

Nutrition and Metabolism (14 decks)

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