Term
| What are the fat-soluble vitamins? |
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Definition
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Term
| What are the essential macrominerals? |
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Definition
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Term
| What are the essential microminerals? |
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Definition
Fe
I
Zn
Se
Cu
Mn
Mo
Co
F (controversial) |
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Term
| What are the functions of micronutrients? |
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Definition
-cofactors in enzymatic reactions
-metalloenzymes (e.g. Fe in redox rxns)
-Binding & transport
-Oxidant defense
-Hormone & Cell Signaling Functions
-Structural Roles
-various brain functions |
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Term
| What are Group I Mictronutrients? |
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Definition
Control type II steroid hormone receptors
iodide, Vit A, Vit D |
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Term
| What are Group II Micronutrients? |
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Definition
work together in oxidant defense
Vit E
Selenium
Vit C |
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Term
| What are Group III Micronutrients? |
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Definition
they act as enzyme cofactors
e.g. thiamin, niacin, riboflavin, biotin, pantothenic acid, B12, B6 folate |
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Term
| What are Group IV Micronutrients? |
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Definition
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Term
| What is the main distinction between vitamins & minerals? |
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Definition
| vitamins are organic, minerals are inorganic |
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Term
| What are the characteristics for classification as a vitamin? |
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Definition
1. exogenous supply is required
2. needed in small amounts
3. organic
4. distinct structure & function from fats, sugars & AA's
5. performs at least 1 unique & essential biochemical function
6. characteristic disease results when it is lacking, poorly absorbed or poorly used |
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Term
| What are steroid hormone receptors? |
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Definition
| intracellular proteins which bind to hormones & become transcription factors |
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Term
| What are the two types of steroid hormone receptors? Where are they localized in the cell, and what do they bind to? |
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Definition
Type I: cytosolic, respond to estrogens, testosterone, progesterone, glucocorticoids
Type II: nuclear, bind to steroid & non-steroid ligands e.g. thyroid hormone retinoic acid, calcitriol |
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Term
| What is the circulating form of iodine? |
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Definition
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Term
| How does iodide move from the GIT into the bloodstream? |
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Definition
| passive diffusion through transporters |
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Term
| How does iodide enter the thyroid? |
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Definition
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Term
| Describe the action of the thyroid gland & TSH |
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Definition
1. Iodide is incorporated into hormones T3 & T4 by post-translational modification
2. T4 is targeted to liver, converted to T3
3. T3 from thyroid & liver interacts with THR, regulates metabolic rate
4. If T3 levels are low, pituitary releases TSH
5. TSH signals for increased T3 & T4 production |
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Term
| What happens if there is not enough iodide available to support the demand for T3 hormone? |
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Definition
| metabolic rate decreases, pituitary will continue to secrete thyroid stimulating hormone (TSH) which leads to hyperplasia of the thyroid (goiter) |
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Term
| What is more regulated, the release of T3 directly from the thyroid, or the conversion T4 stored in the liver to T3? |
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Definition
| direct release from thyroid |
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Term
| What is the bioactive form of thyroid hormone? |
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Definition
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Term
| If thyroid hormone receptors do not have any bound T3, what happens? |
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Definition
| gene expression / production of growth hormone is suppressed (THR acts as a repressor) |
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Term
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Definition
| irreversible mental retardation from fetal hypothyroidism |
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Term
True or False
Both goiter & cretinism are curable |
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Definition
False
Goiter is, cretanism is not. |
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Term
| What protein is modified in the synthesis of T3 & T4? |
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Definition
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Term
| Describe the synthesis of intermediates and their action during the early stages of T3/T4 synthesis |
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Definition
-iodide + hydrogen form iodide intermediates
-intermediates cause iodination & polymerization of tyrosine residues on surface of thyroglobulin |
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Term
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Definition
-increases thyroglobulin synthesis
-increases iodide peroxidase activity
-increases proteolysis of modified thyroglobulin/release of T3 & T4 |
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Term
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Definition
| organic compound from a plant/animal source which is ingested and will either be directly used, or converted to an active metabolic form or storage form |
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Term
True or False
The conversion of retinal to retinol is reversible |
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Definition
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Term
True or False
the conversion of retinol to retinoic acid is reversible |
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Definition
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Term
| What can retinol be converted to? |
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Definition
| retinoic acid or retinyl palmitate |
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Term
| What are the 2 possible fates of beta carotene? |
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Definition
1. go to chylomicron for storage
2. converted to retinyl palmitate to form retinol |
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Term
True or False
Dietary carotenoids can can cause vitamin A toxicity |
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Definition
False
High levels of Vit A will downregulate the conversion of B-carotene to retinol, it will instead be sent to chylomicrons for storage |
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Term
| What is the inactive form of retinol? |
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Definition
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Term
| What is hypercarotenosis? |
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Definition
| high levels of beta carotene stored in adipose tissue can cause subcutaneous fat to turn yellow/orange |
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Term
| Describe the passage of beta carotene/Vit A through the body to its target tissue, assuming that it will not be stored in adipose tissue |
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Definition
-B carotene is converted to retinal, then to retinol, then to retinyl palmitate in stellate cells
-retinyl palmitate is converted to retinol, which binds to RBP
-retinol is released from RBP when needed and targeted to the necessary tissue
-tissue converts retinol to 11-cis-retinal or retinoic acid |
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Term
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Definition
| fibroblasts which store vitamin A |
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Term
| What pigment in the rod cells of retina is important in night vision |
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Definition
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Term
| Describe the importance of Vit A status on the formation of rhodopsin |
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Definition
| Vit A is eventually converted into all-trans retiinol and then 11-cis retinal, combines with opsin forms, rhodopsin |
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Term
| What happens when light strikes rhodopsin pigment in the retina? |
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Definition
-11-cis retinal is converted to all-trans retinol
-all trans form cannot interact with opsin, degradation into free opsin & free all-trans retinal occurs
-degradation releases nerve impulse into optic nerve which enables night vision |
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Term
| What happens when animals are fed only retinoic acid? |
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Definition
-retinoic acid cannot be converted back to retinol or retinal
-rhodopsin cannot be formed
-poor night vision |
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Term
| What is effect of Vit A deficiency on vision? |
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Definition
-poor night blindness (no rhodopsin formed)
-build up of keratin in conjunctiva |
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Term
| What is the effect of Vit K deficiency on growth, fertility & fetal development? |
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Definition
| -impaired growth of long bones, tooth decay -decreased sperm formation -increased fetal resorption -fetal developmental defects due to impaired cell differentiation |
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Term
| What is effect of Vit A deficiency on epithelial cell differentiation? |
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Definition
poor differentiation of various cells for different functions e.g. lungs, trachea, cornea, sclera, GIT, esophagus, skin
-can cause blindness, life threatening infections |
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Term
True or False
Fetal developmental defects are a risk with both too little & too much Vitamin A |
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Definition
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Term
| What are the effects of excessive Vit A intake? |
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Definition
-retinyl palmitate is stored in stellate cells of the liver
-cells get filled to capacity, can cause liver cell death & liver failure |
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Term
True o False
Excessive Vit A intake can be lethal |
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Definition
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Term
| What is the importance of retinoic acid signaling? |
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Definition
| -RA can bind to various receptors, heterodimerize with other receptors etc. to regulate growth pathways & cell differentiation |
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Term
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Definition
estimate average requirement
-meets the needs of 1/2 the population |
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Term
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Definition
recommended daily allowance
-meets the needs of 97-98% of the population |
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Term
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Definition
adequate intake
-used when an EAR & RDA cannot be determined, estimates the amount required to promote health |
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Term
True or False
A nutrient has either an RDA or an AI but never both |
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Definition
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Term
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Definition
tolerable upper intake level
-highest possible intake of a nutrient with no risk of adverse health effects |
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Term
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Definition
acceptable macronutrient distribution range
-% range of protein, fat & CHO that is associated with reduced risk of chronic disease while providing adequate intake of essential nutrients |
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Term
| What is TI? Is a larger or smaller TI better? At what point is a TI considered to be problematic for population health? |
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Definition
Therapeutic Index
UL/RDA
-proportionate safety range for nutrient intake
-the bigger the better
-less than 10 is problematic |
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Term
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Definition
Retinol Activity Equivalents
ug of dietary retinol + (ug dietary b carotene /12) + (ug other carotenoids / 24) |
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