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Nutrition 1 Part 2 > Vitamin D > Flashcards

Vitamin D Flashcards

(80 cards)

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1
Q

what form of vitamin D is cholecalciferol

A

Vitamin D3

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2
Q

What form of vitamin D is ergocalciferol

A

Vitamin D2

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3
Q

Vitamin D3 is synthesized where?

A

epidermis of the skin from UVB

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4
Q

Sources of Vitamin D3

A

fish, eggs, dairy, UVB

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5
Q

Sources of Vitamin D2

A

mushrooms, dairy

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6
Q

_____ absorbs UV photons producing provitamin D2

A

ergosterol

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7
Q

_____ has unstable bonds that rearrange with heat forming ergocalciferol

A

PREvitamin D2

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8
Q

where is provitamin d3 (7-dehydrocholesterol) synthesized

A

in the sebaceous glands of skin from cholesterol

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9
Q

what does provitamin d3 absorb

A

UV photons and is then converted to precalciferol (previtamin d3)

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10
Q

precalciferol has ____ bonds that rearrange in 2-3 days resulting in _____

A

precalciferol has UNSTABLE bonds that rearrange in 2-3 days resulting in CHOLECALCIFEROL

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11
Q

cholecalciferol diffuses from what?

A

skin, into blood

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12
Q

how is cholecalciferol transported to blood

A

by vitamin D binding protein DBP (transcalciferin)

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13
Q

dietary vitamin d in association with dietary fats in packaged into what? how?

A

into micelles with the aid of bile

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14
Q

vitamin d is absorbed how? where?

A

passive diffusion in the distal small intestine

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15
Q

vitamin d from the skin is transported how?

A

diffuses directly into the blood and id pick up by DBP for transport

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16
Q

where does vitamin d from the skin on the DBP travel

A

to the liver, but it can be picked up by other tissues (adipose, mm)

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17
Q

dietary vitamin d is incorporated into what for transport

A

chylomicrons within the enterocytes for transport

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18
Q

chyloomicron remnants deliver the vitamin D where?

A

liver

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19
Q

where else can the vitamin d in the chylomicrons be transferred to DBP for delivery?

A

to extrahepatic tissues

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20
Q

25-hydroxy vitamin D3 aka____

A

calcidiol

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21
Q

25-(OHD3) synthesized from vitamin d in the _____ by what?

A

25-(OHD3) synthesized from vitamin d in the liver by 25-hydroxylase

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22
Q

what cofactor is required for the synthesis of 25(OHD3) from vitamin d?

A

Mg

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23
Q

what is the main circulating form of vitamin d and most accurately reflects vitamin d levels

A

25-OHD3

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24
Q

1,25 dihydroxy vitamin d3 (1,25 (OH)2 D3) aka_____

A

calcitriol

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25
where is 1,25 (OH)2 D3 synthesized and from what and via what enzyme
in the kidney, from 25-OHD3, 1-hydrozylase
26
which is the active form of vitamin D
1,25 (OH)2 D3
27
1,25 (OH)2 D3 OR 25-OHD3 functions as a steroid hormone
1,25 (OH)2 D3
28
vitamin d activity is regulated by_____
1-hydrozylase activity
29
1-hydroxylase is stimulated by
PTH low plasma Ca low 1,25 (OH)2 D3 [ ]
30
1-hydroxylase is inhibited by
high 1,25 (OH)2 D3 [ ] high plasma Ca high K intake
31
when 1,25 (OH)2 D3 levels are high, there is an increased conversion into _______ and conversion of 25-OHD3 into _______
when 1,25 (OH)2 D3 levels are high,there is an increased conversion into 1,24,25 (OH)3 and conversion of 25-OHD3 into 24,25 (OH)2
32
cholecalciferol is sotred mainly in the :
liver and adipose tissue
33
25-OH is store primarily in the
blood and muscle
34
vitamin d functions as:
steroid hormone
35
Vitamin d actions are mediated through what
VDR
36
inside the cell 1,25 (OH)2 + VDR bind to what
VDREs
37
1,25 (OH)2 + VDR + VDREs do what
initiate a cascade of molecular interaction that modulate the transcription of specific genes.
38
Vitamin D is essential for the efficient utilization of ______ in the body
calcium
39
Parathyroid gland secrets PTH when calcium levels are ____
low
40
PTH stimulates the activity of
1-hydroxylase in the kidney
41
PTH of 1-hydroxylase int he kidney results in
increase conversion of 25-OH to the active calcitriol
42
increased calcitriol production restores normal serum calcium levels in what 3 ways
- activation vitamin d transport system - stimulating production and maturation of osteoclasts - increasing the reabsorption of calcium in the distan renal tubules
43
PTH increases or decreases calcium mobilization
increases
44
the process of calcium homeostasis is controlled by
negative feedback loop - where increasing serum calcium and calcitriol levels inhibit PTH secretion and calcitriol production
45
______ is required for the differentiation of many cell types
calcitriol
46
calcitriol is required for the differentiation of WHAT cell types
skin epidermis premyeloid WBCs, stem cells into macrophages and monocytes stem cell monocytes in the bone marrow into mature osteoclasrs
47
calcitriol inhibits what cell type proliferation
fibroblasts, keratinocytes, lymphocytes | abnormal intestinal lymphatic, mammary and skeletal cells
48
true or false: calcitriol can induce cell apotosis
true
49
low vitamin d levels are associated with increasde risk of developing and dying from several cancers including
``` prostate breast colon ovarion non-hodgkins lymphoma ```
50
________ is a potent immune system modulator
1,25 OH2
51
VDR is expressed by most cells including
t cells, APCs
52
inadequate vitamin d levels are linked with what other diseases
RA, crohns, MS, DM 1
53
____ plays a role in insulin secretion
1,25 OH2
54
T or F, adequate Vitamin D levels are important for decreasing risk of high BP
true
55
Vitamin D metabolites are excreted in the
feces (70%) and urine
56
the amount of vitamin d produced in the skin depends on what
``` season level of latitude time of day degree of pigmentation age ```
57
in vitamin D deficiency ______ absorption cannot be increased enough to satisfy the bodys needs
calcium
58
when calcium absorption is not enough to satisfy the bodys needs _____ is increase and calcium is mobilized from the skeleton to maintain normal serum calcium levels
PTH
59
In children vitamin D deficiency is called
rickets
60
signs and sx of rickets
``` bone mineralization defects dental abnormalities growth retardation muscle weakness seizures ```
61
bone minerailzation defects in rickets result in
``` enlarged joints legs bow, knees knock spine becomes curved pelvic and thoracic deformities delayed closure of fontanels ```
62
in adults vitamin d deficiency is called
osteomalacia
63
signs and sx of osteomalacia
``` bone mineralization defects mm weakness low back pain/ aches fatigue sweating ```
64
increased risk of vitamin D deficiency in
``` insufficient sun exposure exclusively breast fed infants dark skin aging obesity fat malabsorption syndromes ```
65
people with dark coloured skin synthesize LESS OR MORE vitamin D than light colour skin
less
66
the elderly have a INCREASED OR REDUCED capacity to synthesize vitamin D when exposed to UVB
reduced
67
once vitamin d is synthesized in the skin or ingested, it is deposited _____
body fat stores
68
the vitamin D in body fat stores makes vitamin d LESS OR MORE bioavailable
less
69
vitamin D supplementation is clinically indicated for
osteoporosis | cancer prevention
70
the preferred form for supplementation is
cholecalciferol (D3)
71
hypervitaminosis D induces what
abnormally high serum calcium levels
72
abnormally high serum calcium levels could result in
kidney stones | calcification of soft tissues
73
certain medical conditions can increase the risk of hypercalcemia in response to vitamin D.....what are they
``` hyperparathyroidism sarcoidosis TB lymphoma * increased caution should be taken when supplementing these individuals ```
74
which is more toxic D2 or D3
D2
75
T OR F - excessive sun exposure is not associated with risk of vitamin d toxicity
true
76
signs and sx of hypervitaminosis D
``` hypercalcemia hypercalciuria loss appetite, constipation, n/v mm weakness hypertension and cardiac arrythmias calcification of soft tissues renal dysfxn mental confusion death ```
77
Vitamin D increased the intestinal absorption of what two minerals
Ca and P - promotes deposition into bone
78
what mineral is required for the conversion of vitamin d3 to 25(OH)D3
Mg
79
synthesis of what vitamin dependent proteins are stimulated by 1,25OH2
Vitamin K
80
what is the best indicator of vitamin d status
serum 25 (OH)

Nutrition 1 Part 2 (23 decks)

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