Term
| What is/are the function(s) of Vit D? |
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Definition
-precursor for forming calcitrol
-can also bind directly to cell surface receptor to control cell signaling |
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Term
| What is/are the function(s) of Vit K? |
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Definition
| -post translational modification of proteins so that they can bind to calcitrol |
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Term
| What is calcitriol/what does it do? |
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Definition
| A regulator of cellular function, binds to VDR & controls gene expression |
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Term
| What is/are the function(s) of Calcium? |
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Definition
-support & storage in bones in the form of hydroxyapatite
-cell signaling, nervous transmission, muscle contraction |
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Term
| What is/are the function(s) of Phosphorous? |
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Definition
| -key role in protein phosphorylation (post-translational control) |
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Term
| What is/are the function(s) of Fluoride? |
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Definition
| -forms fluoroapatite, found in dentine layer of teeth and also in bone |
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Term
| What happens if calcium levels in blood / extracellular regions drops or drastically increases? |
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Definition
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Term
| What are the common sources of vit D? |
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Definition
-from plants
-in/from animals
-sun exposure
-supplementation
-fortification |
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Term
| Where is 7-dehydrocholesterol found, and what vitamin is it related to? |
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Definition
| in sebaceous glands of animals' skin, or keratinocytes of epidermis |
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Term
| What happens when 7-dehydrocholesterol is exposed to heat / UV? Where can this product be found in natural food sources? |
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Definition
converted to cholecalciferol (D3)
-can be found in fish & fish liver oils |
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Term
| If supplementing Vit D in the diet, what form should be used and how is it best absorbed? |
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Definition
| D3 should be used, in conjunction with a lipid for best absorption as it is fat soluble |
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Term
| Describe the absorption of Vit D from the sun |
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Definition
-skin absorbs UV & IR, 7-dehydrocholesterol converted to vit D3
-Vit D3 goes to adipose tissue then to liver when needed, or directly to liver
-Vit D converted to calcidiol, travels through bloodstream to kidney where it is converted to calcitriol
-calcitriol is targeted to bones, intestinal mucosa or stored in kidneys |
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Term
| What is the concentration of circulating calcidiol reflective of? |
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Definition
| -nutritional status in terms of vit D, varies with diet/sun |
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Term
| Describe the absorption of dietary vit D |
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Definition
-vit D travels from SI lumen through intestinal mucosa via icelle
-vit D is bound to chylomicron, when becomes chylomicron remnant and is targeted to liver
-vit D is converted to calcidiol, circulates in bloodstream, travels to kidneys
-converted to calcitriol and either targeted to bone, intestinal mucosa or stored in kidneys |
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Term
| What is the active hormone of Vit D? |
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Definition
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Term
| That stimulates the synthesis of calcitriol? |
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Definition
| secretion of parathyroid hormone (PTH) |
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Term
| What is Path 1 in calcitriol signaling? |
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Definition
-calcitriol enters cell's nucleus, binds to vit D receptor (VDR) to form a transcripion factor
-promotes transcription, synthesis of calcium binding proteins
- |
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Term
| What is Path 2 in calcitriol signaling? |
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Definition
-calcitriol binds to cell surface receptor
-stimulates protein phosphorylation
-signals regulation of various proteins including Ca transporters |
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Term
| What does MARRS stand for? What is it? |
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Definition
Membrane-Associated Rapid Response Steroid
-cell surface receptor for calcitriol |
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Term
| What are the effects of calcitriol signaling in bone? |
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Definition
calcitriol + PTH causes osteoblasts to increase expression of RANK ligand
-RANK ligand activates/ increases activity of osteoclasts |
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Term
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Definition
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Term
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Definition
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Term
| Why are osteoclasts active when calcitronin & PTH levels are low? |
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Definition
| to increase resorption of calcium |
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Term
| What are the effects of calcitriol signaling in intestinal mucosal cells & kidney tubules? |
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Definition
-Ca binding proteins are synthesized, which require vit K dependent gamma-carboxylation
-Ca binding proteins cause increase absorption & reabsorption of calcium |
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Term
| Gamma-carboxylation is dependent on what? |
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Definition
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Term
| Where does absorption of Vit D / Calcium occur, and how does it happen? |
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Definition
-in small intestine
-transporters carry across mmb into mucosal cell, and also across mmb into blood stream |
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Term
| Proper absorption of calcium depends on what? |
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Definition
| expression of calcium binding proteins in epithelial cells |
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Term
| Where does reabsorption of Vit D / Calcium occur and how does it happen? |
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Definition
| -in kidneys -molecules circulate in blood, reach kidney, pass through filter, will either enter urine or be reabsorbed -reasorption removes molecules from filtrate and releases them into blood |
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Term
| Where does resorption of calcium occur, and what is it? |
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Definition
in the bone
-calcitriol & PTH stimulate osteoclasts to dissole bone structure & release calcium into bloodstream |
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Term
| What are the calcium hormonal control systems? Specify their effect on blood calcium |
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Definition
Parathyroid Hormone (increases)
Vitamin D (increases)
Calcitonin (decreases) |
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Term
| What does parathyroid hormone do, and from where is it secreted? |
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Definition
secreted from parathyroid glands
-increase blood calcium
-stimulates calcitriol production in kidneys
-maximizes tubular reabsorption of calcium in kidney |
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Term
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Definition
-increases blood calcium
-stimulates resorption of bone
-facilitates absorption of Ca from SI
-maximizes tubular reabsorption of calcium in kidney |
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Term
| What does calcitonin do, and from where is it secreted? |
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Definition
secreted by parafollicular cells
-decreases blood calcium
-suppresses tubular reabsorption of calcium in kidney
-inhibits bone resorption, facilitates remineralization |
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Term
| What are the effects of a vit D deficiency? |
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Definition
-decreases intestinal calcium absorption
-decreases tubular calcium resorption
-decreased bood resorption (due to PTH) |
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Term
| What is Rickets disease, and what age group is most affected? |
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Definition
-soft bone due to lack of minerals, bone malformation
-infants are at risk |
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Term
| What is osteomalacia, and what age group is most affected? |
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Definition
demineralization of properly formed bones, can lead to fractures
-adolescents & adults are at risk |
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Term
| What is osteoporosis, and what age group is most affected? |
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Definition
-weaknening of bones which is enhanced by Ca/Vit D deficiency, can lead to fractures
-elderly are at risk |
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Term
| Why is there no risk of vit D toxicity due to sun exposure? |
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Definition
| production of vit D is limited by amounts of 7-dehydrocholesterol in skin |
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Term
| What are the effects of a dietary intake of vit D beyond the UL? |
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Definition
D is absorbed, incorporated into chylomicrons, remnants deliver vit D to liver, it is hydroxylated, returns to bloodstream
-excess can cause hypercalcemia, possible calcification of soft tissues |
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Term
True or False
there is very little storage of vit K in the body, so newborn babies are given vit K injections to prevent hemorrhaging |
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Definition
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Term
| What are the forms of vit K in plants and bacteria? Are their sidechains saturated / unsaturated? |
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Definition
Plants: phylloquinone, saturated
Bacteria: menaquinone, unsaturated |
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Term
| What is the function of vit K on gamma carboxylase enzymes? |
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Definition
| acts as a prosthetic group, enabling gamma carboxylation of proteins to produce calcium binding proteins |
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Term
| What vitamin is involve with blood clotting? |
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Definition
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Term
| What inhibits the conversion of inactive vit K to the active form? |
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Definition
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Term
| Describe the processes vit D & K are involved with in the production of calcium binding proteins |
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Definition
1. Vit D enables transcription & translation of a pre-calcium binding protein
2. Vit K enables post-translational modification, adding a gamma-carboxyglutamate sidechain
3. Result is a Ca-binding protein |
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Term
| What are the symptoms of vit K toxicity? |
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Definition
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Term
| What are the symptoms of vit K deficiency? |
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Definition
-impaired blood clotting
-impaired activation of calcium binding proteins |
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Term
| Where is intracellular calcium stored? |
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Definition
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Term
| how is intracellular calcium released? |
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Definition
| binding of receptor causes release to transduce signal for neurotransmission, gene expression etc. |
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Term
| Compare the concentration of intracellular calcium to blood calcum |
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Definition
Intracellular: low & variable
Blood: high & constant |
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Term
True or False
All blood calcium is bound in proteins |
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Definition
False
Approx. 1/2 is bound in proteins |
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Term
| Describe the storage of calcium in bones |
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Definition
99% in mineral phase
1% in a pool which can exchange w/ extracellular calcium |
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Term
True or False
the concentration of blood calcium is almost identical to that of phosphorous |
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Definition
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Term
| What are some effects of calcium deficiency? |
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Definition
-inadequate bone mineralization
-decreased muscle strength, motor nerve function
-associated with hypertension & colon cancer |
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Term
| What are some effects of calcium toxicity? |
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Definition
constipation
hypercalcemia (kidney stones) |
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Term
| What is the function of phosphorous? |
|
Definition
-mineralization in bone
-central to all forms of metabolism
-important in protein phosphorylation/posttranslational control of proteins |
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Term
| What are some effects of phosphorous deficiency? |
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Definition
| this kind of deficiency is very rare |
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Term
| What are some effects of phosphorous toxicity? |
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Definition
| very rare, but high intake can encourage loss of Ca+ |
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Term
True or False
If intake of other nutrients is adequate, the intake of phosphorous is also likely to be adequate |
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Definition
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Term
| What are the functions of fluoride? |
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Definition
-formation of fluroapatite (in tooth enamel)
-this increases resistance of enamel to bacteria-induced degradation |
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Term
| What are some effects of fluoride deficiency? |
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Definition
| -increased evidence of tooth decay |
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Term
| What are some effects of fluoride toxicity? |
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Definition
| -dusty white patches on teeth |
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Term
True or False
There is a fine line between maximum protection from bacterial degradation & fluorosis |
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Definition
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