Week 3 (2) Micronutrient Lectrues Flashcards
what are micronutrients?
nutrients that are only required in SMALL (micro) amounts
can we take make micronutrients in sufficient quantitiies?
no, we cannot make them in sufficient quantities
what is the major difference between micronutrients and macronutrients?
micronutrients are not metabolized directly to provide energy
what are the two large classes of micronutrients?
fat soluble (ADEK) and water soluble (C and B complex)
what is another word for micronutrients? 2
vitamins and minerals
what is unique about vitamin A? what is the purpose?
highly conjugated, able to absorb visible light
like any lipid soluble molecule, the lipid soluble vitamins (ADEK) have to be transported how in blood?
via lipoproteins/carrier proteins (chylomicrons, VDL, HDL), but they can easily diffuse across plasma membranes
chylomicrons–>liver–>VLDL(LDL)–>Tissue
where do lipid soluble vitamins accumulate?
in body tissues/organs/fat
what is the danger of lipid soluble vitamin accumulation?
mega-doses (100x RDA), can lead to metabolic consequences
Vitamin D deficiency is linked to which bone disorder?
rickets
Vitamin D is derived from what?
sterols
what is a pro-vitamin?
a vitamin that is not yet in its active form
how is the vitamin D3 pro-vitamin activated?
UV light
Vitamin D3 is the precursor for what active endgoenous metabolite?
calcitriol
in order for vitamin D3 to be converted/activated to calcitriol what must occur
- pro-vitamin is activated by UV light to form vitamin D3
2. D3 must be hydroxylated twice (in liver and then in kidney) to form the active calcitriol
the formation of calcitriol is regulated at what level?
in the kidney/bone during the second hydroxylation event
what is the function of calcitriol?
maintains plasma calcium homeostasis in conjunction with PTH (promotes transcription of genes associated with calcium uptake from duodenum)
a decrease in plasma Ca will cause what?
an increase in parathyroid hormone–>an increase in calcitriol–>increase in Ca absorption in intestines
vitamin D deficiency can lead to what in adults?
osteoporosis. a decrease in bone mass and fragile bones
what are some conditions associated with vitamin D toxicicty (>10X RDA)
hypercalcemia, calcium deposits in kidney and heart
when we say that vitamins are a family of molecules what does that mean?
A mixture of forms all of which have some activity. Ex. Vitamin A comprises a family of molecules containing a 20 carbon structure….retinal and retinoic acid
what is the biologic function of vitamin A? 2
vision: retinol binds rhodopsin and when light hits it, it is converted to the all trans form
gene expression: retinoic acid binds receptor and regulates expression of genes associated with proliferation and differentiation (integrity of epithelial cells, maintain immune function, embryonic development)
what is the active from of Vitamin A? (2)
retinol (eyes), retinoic acid (gene expression)
Vit A deficiency causes? 2
night blindness, skin lesions
vitamin E has how many naturally occurring forms?
8, all hydrophobic in nature
what is fxn of Vit E?
anti-oxidant (non-specific) protect poly-unsaturated FAs from becoming oxidized. a specific metabolic fxn has yet to be found
where do you find Vit E most commonly?
found in commercially produced oils and lotions to preserve them
Vitamin K is acquired how?
diet and intestinal bacteria
what is the role of Vit K? 2
cofactor in carboxylation reactions (plays role in calcium binding). carboxylated products important in coagulation and stimulation of bone and mineral maturation
if you are def in VIt K?
bleeding, lack of clotting
is vit K def common?
rare in adults but more common in infants due to sterile guts
what is vitamin E def?
none discovered
compared to the fat soluble vitamins, the water soluble vitamins are much more
polar (O, N, charged)
which water soluble vitamin is conjugated?
Vitamin B (light sensitive, store in dark to prevent degradation)
how are water soluble micronutrients absorbed
CANT diffuse across membranes, need membrane transporters
are water soluble micronutrients easy to overdose on?
no, they are more easily excreted than the lipid soluble ones AND they saturate membrane transport proteins (M-M kinetics)
in general, the water soluble vitamins and minerals play an important role in…
once processed, serve as co-factors for different metabolic (energy producing) pathways. NAD, FAD, CoA
Thiamin is also called
B1
what is the active form of B1
TPP
what is the fxn of thiamin?
important co-factor for metabolic enzymes. Ex: pyruvate dehydrogenase complex
what is the fxn of thiamin?
important co-factor for metabolic enzymes. Ex: pyruvate dehydrogenase complex…others
what is the source of thiamin? 3
whole grains, enriched flour, meats
factors that destroy thiamin? 3
heat, thiaminase (raw fish), tannins
thiamin deficiency**
Beriberi (be able to associate beriberi and thiamin deficiency)
vitamin B2 is also called
riboflavin
what is riboflavin converted to?
FAD (succinate dehydrogense requires this)
where can we get riboflavin? 5
milk, grains, meat, poultry, fish
another name for B3 is
niacin
niacin is converted to?
NAD and NADP
Niacin can be made from…
Tryptophan
niacin deficiency disease***
the 3 D’s Dermatitis, Dementia, Diarrhea
B5 is aprecursor for
CoA (TCA cycle!, beta oxidation)
B6 is a family of
a group of 6 pyrimidine derivatives
are vitamin B deficencies commonq
no, they are in abundance in our diets
are vitamin B deficencies commonq
no, they are in abundance in our diets
B6 fxn?
a coenzyme for >100 enzymes. w/o B6 all AA become essential
Vitamin B7 AKA
biotin
role of biotin
coenzyme in carboxylation reactions (pyruvate carboxylase)
B9 aka
Folic acid
folic acid role
carbon metabolism (AA, purine and thymidine synthesis)
B12 family role
involved in methionine synthesis (coenzyme for methionine synthetase)
what is unique about B12 absorption?
unlike other water soluble vitamins, it requires a protien (intrinsic factor) to be absorbed in the intestines
Vitamin C aka
ascorbic acid
role of Vit C (2)
anti-oxidant, aids hydroxylation (important in collagen formation)
Vit C deficiency
Scurvy: failure to cross-link collagen (weak bones)
important Minerals
Fe (Hb), I (thyroid), Zn, Se
Keshan disease associated with what mineral def?
Se
Selenium role?
forms selenoproteins that play a role in defending against oxidative damage, disulfide bond homeostasis, thyroid hormone metabolism
Zn fxn
essential in fxn of many enzymes and TFs
