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NUTR2101 > Revision questions - week 9 > Flashcards

Revision questions - week 9 Flashcards

1
Q

How does vitamin K help in the formation of blood clots?

A

as a cofactor of the carboxylase enzyme in the synthesis of blood clotting factors and the conversion of preprothrombin to prothrombin in the liver

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2
Q

How does Warfarin ( blood thinning medication) interfere with vitamin K activity?

A

?

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3
Q

Vitamin A - various forms in diet and where found

A 
retinoids 
 - retinal
 - retinol
 - retinoic acid
 - found in liver, beef, eggs, dairy
carotenoids
 - alpha - carotene
 - beta - carotene
 - beta - cryptoxanthin
found in orange veges/fruits and spinach
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4
Q

Vitamin A - bioloigcally active form

A

retinoids

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5
Q

Vitamin A - deficiency and toxicity

A 
deficiency
 - xerophthalmia - dryness of eye
 - keratomalacia - blindness
toxicity
 - acute - upset GI and muscle incoordination
 - chronic - liver damage and bone loss
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6
Q

VItamin A - functions with mechanisms on the light-dark adaptations of eye

A
  • in our cones we have rhodopsin, which is a combination of opsin and II cis-retinal. when it absorbs light converts to II-cis-retinal to aII-trans-retinal. this AII - trans retinal will convert back to rhodopsin
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7
Q

Vitamin A - IU equivalent

A

1IU = 0.3ug

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8
Q

Vitamin A - digestion

A
  • retinyl esters split into retinol and fatty acids in GIT via bile and pancreatic lipase activity
  • provitamin A carotenoids usually bind to protein molecules ini food and is split via enzyme activity in GIT for absoprtion
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9
Q

Vitamin A - Absorption

A
  • 90% retinol intake via carrier proteins

- 5-60% carotenoids by passive diffusion

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10
Q

Vitamin A - transport

A

Enterocytes
- reinyl esters reformed, packaged in chylomicrons, transported via the lymphatic system to bloodstream and liver
- retinoic acid enters bloodstream directlu and is transported to liver
- carotenoids can also enter circulation directly (those not transformed carried by VLDL)
From liver
- retinoids bound to retinol binding protein for transport to cell

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11
Q

Vitamin A - storage

A
  • > 90% liver

- small amounts in adipose tissue, kidney, bone marrow, testicles, eyes

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12
Q

Vitamin A - excretion

A
  • small amounts in urine

- carotenoid as bile

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13
Q

Vitamin A - activation

A
  • Carotenoids cleaved to form retinal or retinoic acid

- Retinal converted to retinol and retinoic acid

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14
Q

Vitamin A - RDI and UL

A 
RDI 
 - men:900ug or 3000IU
 - women: 700ug or 2333IU
UL
 - men and women : 3000ug or 10000IU
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15
Q

Vitamin D - biologically active form

A

calcitriol

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16
Q

Calcitriol from endogenous precursor

A
  • conversion of 7-dehydrocholesterol in skin to vitamin D3 upon UVB exposre
  • hydroxylation in liver to 25 hydroxy vitamin D3
  • hydroxylation in kidney to 1,25hydroxy vitamin D3 (calcitriol)
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17
Q

Vitamin D - IU equivalent

A

1ug = 40IU

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18
Q

Calcitriol in calcium homeostasis

A

maintains blood concentration of clacium and phosphorus

- aids in increasing absorption of dietary calcium from GIT and in releasing calcium from bone if required

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19
Q

Vitamin D - food source

A

D3 - fish/fish oil
D2 - supplementationor fortified foods
also from sunlight and cholesterol

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20
Q

Vitamin D - absorption

A
  • micelles and enterocytes (dependant on bile and pancreatic lipase)
  • into chylomicrons thorugh lymphatic system and into circulation to the liver
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21
Q

Vitamin D - deficiency

A
  • rickets
  • Osteomalacia - soft sore bones
  • Related to: season, location, ageing skin, liver and kidney disease, dark skin, intestinal disease
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22
Q

Vitamin D - toxicity

A
  • hypercalcemia - bone demineralisation
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23
Q

Vitamin D - transport

A

from liver via lipoproteins for tissue delivery

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24
Q

vitamin D - storage

A

in adipose tissue, liver and kidney

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25
Q

Vitamin D activaation

A

Conversion to active form regulated by parathyroid hormone – takes place in liver and kidneys

26
Q

Vitamin E - food source

A

sunflower seeds and oil, mayonaise

27
Q

Vitamin E digestion

A
  • depends on dietary fat and amount consumed

passive diffusion

28
Q

vitamin E absorption

A

20-70% dietary intake is usually absorbed

29
Q

Vitamin E transport

A
  • Micelles to enterocytes: dependent on bile and pancreatic lipase 

  • Chylomicrons, through lymphatic system and into circulation, peripheral tissues and to the liver 

  • Transported from liver via lipoproteins (VLDL, LDL, HDL,) for tissue delivery 

30
Q

Vitamin E - Storage

A

90% stored in adipose tissue

31
Q

Vitamin E - excretion

A

bile, urine, skin

32
Q

Vitamin E activation

A

Alpha tocopherol – most biologically active form

33
Q

Vitamin E AI

A

men 10mg or 15IU

women 7mg or 10.5IU

34
Q

Vitamin E UL

A

300mg or 450IU

35
Q

Vitamin E toxicity

A

Interferes with vit K activity in blood clotting therefore may increase risk of hemorrhaging

36
Q

Vitamin E deficiency

A
  • Hemolytic anemia – premature hemolysis of red blood cells
  • Impaired immune function, neuropathy, retinal damage
  • Oxidative stress related
37
Q

What are the various forms and sources of vitamin E?

A

Alpha, beta, gamma and delta of tocopherols and tocotrienols

alphatocotrienols (natural form) - most potent

38
Q

What is an IU of vitamin E worth?

A 
1IU = 0.667mgalpha-tocopherol(naturalsource)
1IU = 0.45mg alpha-tocopherol (synthetic source) 

39
Q

Vitamin K food source

A
  • Phyloquinones – plants (green leafy veges, broccoli, beans etc) K1 - most potent
  • Menaquinones – bacterial synthesis (produces 10% of daily requirement K2
40
Q

Vitamin K absorption

A
  • Best in presence of fat (since K1 is mainly found in green leafy vegetables), or consumed as vegetable oils (some are rich)
  • 80% of dietary vitamin K absorbed in small intestine, via micelle (lipase and bile activity required)

41
Q

Vitamin K transport

A
  • Taken in chylomicrons through the lymphatic system to the circulation
  • Colonic bacteria can produce menaquinones: absorbed in the colon by passive diffusion
- Transported via lipoproteins (VLDL and LDL) to peripheral tissue
42
Q

Vitamin K storage

A

some in liver

most recycles rapidly in the K-epoxide cycle for optimal use

43
Q

Vitamin K excretion

A

mainly bile and faeces

small amounts in urine

44
Q

Vitamin K activation

A

phylloquinones - most bioloigcally active

45
Q

vitamin K toxicity

A

none

46
Q

vitamin K deficiency

A
  • long term antibiotic use, or fat malabsorption
  • high dose of A can interfere with absorption from GIT
  • high dose of E can interfere with activity on clotting factors
47
Q

Vitamin D mechansim of action involved in bone health

A

Increased calcium absorption in the GIT by upregulating the expression of calcium receptors and transporters in the enterocyte. Increase phosphorous absorption

48
Q

• Evaluate pros and cons of vitamins supplementation in general terms, such as for “antioxidant function”

A

??

49
Q

Vitamin D excess consumption of Vit D supplementation

A

o Can cause over absorption of calcium therefore hypercalcaemia, calcium deposit in kidney, joints, blood vessels, heart
o Can also lead to bone demineralization
o Can be fatal in chronic excess

50
Q

Why would someone taking warfarin have moderate intake of green leafy vege

A

blood thinning medication
because these vegetables contain high concentration of vitamin K which counteracts the activity of Warfarin. This is because this medication inhibits the enzyme that reduces vitamin K (and thus recycles it) after vitamin K acted as a cofactor to the enzyme that gamma-carboxylates pre-prothrombin to prothrombin to produce blood clotting factors.

51
Q

What vitamin is most potent in natural for compared to synthetic form

A

Vit E

52
Q

What vitamin can result in death in both deficiency and toxicity

A

Vit A

53
Q

Why would someone taking blood thinning medication also need to avoid vitamin e supplements

A

because vitamin E in supplements enhances the activity of Warefrin by interfering with vitamin K activity, resulting in a high risk of hemorrhaging when the blood is too thin.

54
Q

The two ways vitamin D assists in blood calcium homeostasis when it has dropped is

A

1) promoting bone resorption to release bone calcium into the blood; 2) increasing the calcium transporter expression in the enterocytes in order to absorb more calcium from the diet

55
Q

provitamin A are ___ that can be converted to ___, and a rich food source would be ___

A

carotenoids;retinoids; mango, sweet potato

56
Q

Preformed vitamin A are __, and a rich food source is ___

A

retinoids;liver or meat

57
Q

The reason new baby are given a vitamin K injection at birth is to

A

to prevent risk of uncontrolled hemorrhaging because their GIT is sterile, and thus they don’t have bacterial production of vitamin K yet and wont consume green leafy vegetables for a while.

58
Q

The RDI for vitamin A is expressed in ____ this means that ?

A

retinol equivalent
the RDI accounts for the retinoids and the carotenoids in the diet, since carotenoids can be converted to retinoids and thus have vitamin A activity.

59
Q

Carotenoids are ____ in value to retinoids

A

not equal

E.g: 6 micrograms of betacarotene are equivalent to 1 microgram of retinol in the conversion.

60
Q

main function of Vit E

A

as an antioxidant - prevents propagation of; free radicals in cell membrane, and LDL through oxidation of lipids

61
Q

main function of Vit K

A

cofactor of carboxylase enzyme in the synthesis of blood clotting factors - conversion of preprothrombin to prothrombin in liver

62
Q

Vit A function with mechanism on the target cells

A
  • vit A enters
  • binds to cellular retinoid binding protein
  • released
  • enters nucleas and binds to RAR and RXR
  • this binds to DNA – activating gene transcription
  • resulting in mRNA
  • protein produces cellular response

NUTR2101 (35 decks)

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