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Nutrition 1 Part 2 > Vitamin D > Flashcards

Flashcards in Vitamin D Deck (80):
1

what form of vitamin D is cholecalciferol

Vitamin D3

2

What form of vitamin D is ergocalciferol

Vitamin D2

3

Vitamin D3 is synthesized where?

epidermis of the skin from UVB

4

Sources of Vitamin D3

fish, eggs, dairy, UVB

5

Sources of Vitamin D2

mushrooms, dairy

6

_____ absorbs UV photons producing provitamin D2

ergosterol

7

_____ has unstable bonds that rearrange with heat forming ergocalciferol

PREvitamin D2

8

where is provitamin d3 (7-dehydrocholesterol) synthesized

in the sebaceous glands of skin from cholesterol

9

what does provitamin d3 absorb

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

10

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

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

11

cholecalciferol diffuses from what?

skin, into blood

12

how is cholecalciferol transported to blood

by vitamin D binding protein DBP (transcalciferin)

13

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

into micelles with the aid of bile

14

vitamin d is absorbed how? where?

passive diffusion in the distal small intestine

15

vitamin d from the skin is transported how?

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

16

where does vitamin d from the skin on the DBP travel

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

17

dietary vitamin d is incorporated into what for transport

chylomicrons within the enterocytes for transport

18

chyloomicron remnants deliver the vitamin D where?

liver

19

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

to extrahepatic tissues

20

25-hydroxy vitamin D3 aka____

calcidiol

21

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

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

22

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

Mg

23

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

25-OHD3

24

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

calcitriol

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)