Revision questions - week 9 Flashcards
(62 cards)
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
2
Q
How does Warfarin ( blood thinning medication) interfere with vitamin K activity?
A
?
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
4
Q
Vitamin A - bioloigcally active form
A
retinoids
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
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
7
Q
Vitamin A - IU equivalent
A
1IU = 0.3ug
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
9
Q
Vitamin A - Absorption
A
- 90% retinol intake via carrier proteins
- 5-60% carotenoids by passive diffusion
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
11
Q
Vitamin A - storage
A
- > 90% liver
- small amounts in adipose tissue, kidney, bone marrow, testicles, eyes
12
Q
Vitamin A - excretion
A
- small amounts in urine
- carotenoid as bile
13
Q
Vitamin A - activation
A
- Carotenoids cleaved to form retinal or retinoic acid
- Retinal converted to retinol and retinoic acid
14
Q
Vitamin A - RDI and UL
A
RDI - men:900ug or 3000IU - women: 700ug or 2333IU UL - men and women : 3000ug or 10000IU
15
Q
Vitamin D - biologically active form
A
calcitriol
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)
17
Q
Vitamin D - IU equivalent
A
1ug = 40IU
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
19
Q
Vitamin D - food source
A
D3 - fish/fish oil
D2 - supplementationor fortified foods
also from sunlight and cholesterol
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
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
22
Q
Vitamin D - toxicity
A
- hypercalcemia - bone demineralisation
23
Q
Vitamin D - transport
A
from liver via lipoproteins for tissue delivery
24
Q
vitamin D - storage
A
in adipose tissue, liver and kidney
25
Vitamin D activaation
Conversion to active form regulated by parathyroid hormone – takes place in liver and kidneys
26
Vitamin E - food source
sunflower seeds and oil, mayonaise
27
Vitamin E digestion
- depends on dietary fat and amount consumed
| passive diffusion
28
vitamin E absorption
20-70% dietary intake is usually absorbed
29
Vitamin E transport
- 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
Vitamin E - Storage
90% stored in adipose tissue
31
Vitamin E - excretion
bile, urine, skin
32
Vitamin E activation
Alpha tocopherol – most biologically active form
33
Vitamin E AI
men 10mg or 15IU
| women 7mg or 10.5IU
34
Vitamin E UL
300mg or 450IU
35
Vitamin E toxicity
Interferes with vit K activity in blood clotting therefore may increase risk of hemorrhaging
36
Vitamin E deficiency
- Hemolytic anemia – premature hemolysis of red blood cells
- Impaired immune function, neuropathy, retinal damage
- Oxidative stress related
37
What are the various forms and sources of vitamin E?
Alpha, beta, gamma and delta of tocopherols and tocotrienols
| alphatocotrienols (natural form) - most potent
38
What is an IU of vitamin E worth?
```
1IU = 0.667mgalpha-tocopherol(naturalsource)
1IU = 0.45mg alpha-tocopherol (synthetic source)
```
39
Vitamin K food source
- Phyloquinones – plants (green leafy veges, broccoli, beans etc) K1 - most potent
- Menaquinones – bacterial synthesis (produces 10% of daily requirement K2
40
Vitamin K absorption
- 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
Vitamin K transport
- 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
Vitamin K storage
some in liver
| most recycles rapidly in the K-epoxide cycle for optimal use
43
Vitamin K excretion
mainly bile and faeces
| small amounts in urine
44
Vitamin K activation
phylloquinones - most bioloigcally active
45
vitamin K toxicity
none
46
vitamin K deficiency
- 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
Vitamin D mechansim of action involved in bone health
Increased calcium absorption in the GIT by upregulating the expression of calcium receptors and transporters in the enterocyte. Increase phosphorous absorption
48
• Evaluate pros and cons of vitamins supplementation in general terms, such as for “antioxidant function”
??
49
Vitamin D excess consumption of Vit D supplementation
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
Why would someone taking warfarin have moderate intake of green leafy vege
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
What vitamin is most potent in natural for compared to synthetic form
Vit E
52
What vitamin can result in death in both deficiency and toxicity
Vit A
53
Why would someone taking blood thinning medication also need to avoid vitamin e supplements
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
The two ways vitamin D assists in blood calcium homeostasis when it has dropped is
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
provitamin A are ___ that can be converted to ___, and a rich food source would be ___
carotenoids;retinoids; mango, sweet potato
56
Preformed vitamin A are __, and a rich food source is ___
retinoids;liver or meat
57
The reason new baby are given a vitamin K injection at birth is to
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
The RDI for vitamin A is expressed in ____ this means that ?
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
Carotenoids are ____ in value to retinoids
not equal
| E.g: 6 micrograms of betacarotene are equivalent to 1 microgram of retinol in the conversion.
60
main function of Vit E
as an antioxidant - prevents propagation of; free radicals in cell membrane, and LDL through oxidation of lipids
61
main function of Vit K
cofactor of carboxylase enzyme in the synthesis of blood clotting factors - conversion of preprothrombin to prothrombin in liver
62
Vit A function with mechanism on the target cells
- 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
