Micronutrients Part 3 Flashcards
What is the third group of micronutrients? Example?
- act as enzyme cofactors
- Niacin, Thiamin, Riboflavin, B6, folate, B12, biotin, pantothenic acid
What are the sources of niacin (vitamin B3)?
- fish, meats
- breads
- cereals
- coffee (roasted beans)
What is the active form of Vit B3 in plants? What about animals?
Plants:
- nicotinic acid
Animals:
- NAD
- NADP
- nicotinamide
How is vit B3 absorbed?
- NAD and NADP is hydrolyzed by glycohydrolase.
- Nicotinic acid and nicotinamide circulate freely and cross membranes by simple diffusion (except kidneys and red blood cells)
- used to synthesis NAPH and NADPH !
Describe the conversion of nicotinic acid to NAD(P)+
- converted to amide (addition of amino group)
- build into dinucleotide structure (ribose + base + phosphate)
Why are populations that consume primarily corn deficient in niacin? How can this be reversed?
- corn is high in niacin, but is bound to non-digestible carbohydrates
- corn is also low in tryptophan (1/60 tryptophan can be converted to niacin)
How is the RDA for niacin calculated? What are the symptoms of niacin deficiency?
- NE (niacin equivalent)
= mg from preformed niacin + mg Trp/60 - 4 D’s : dermatitis, dementia, diarrhea, death
(reversible) - under the term: pellagra
What is the primary form of riboflavin (B2)?
- FAD (60-90%)
What is the relation between iodine intake and riboflavin?
- T3 regulates Riboflavin
- T3 activates Flavokinase
- Iodine is required to produce T4 and T3!
- therefore an iodine deficiency will inhibit the activation of riboflavin.
True or false: there are higher concentrations of NAD+(oxidized) than NADH (reduced) in the cell?
True:
- NAD+ is required in higher amounts to participate in CATABOLISM - glycolysis, Krebs, B-oxidation
- NAD+ is reduced in these processes
True or false: there are higher concentrations of NADP+ than NADPH in the cell?
False:
- NADPH is oxidized to NADP+
- used in the regeneration of glutathione
Why do men need more riboflavin than women?
- Men have larger body size and typically more muscle
–> greater energy expenditure and therefore more cofactor such as FAD to metabolic pathways
TRUE OR FALSE:
The upper limit for riboflavin is 35mg?
FALSE:
there is no upper limit for riboflavin, as any excess is excreted in the urine.
What are some food sources of vitamin B2?
milk, milk products and meats
Where is thiamine (vit B1) found?
- meats
- whole fortified or enriches grain products
What are the 2 major metabolic pathways in which thiamine (TPP) plays a role?
- pyruvate dehydrogenase (pyruvate –> acetyl coA)
- Alpha-ketoglutarate dehydrogenase ( Krebs cycle)
What are the sources of biotin (bit B7)?
- made by intestinal bacteria
- in foods bound to proteins
what must occur for biotin to be absorbed from foods?
- proteolysis by pepsin in the stomach breaks down the proteins and releases biotin?
what is a key metabolic reactions involving Vit B7?
- Pyruvate carboxylation (production of oxaloacetate)
what amino acid residue is involved in the peptide bond with biotin?
- lysine residue in the enzyme
- allows the enzyme to “swing over” to collect and drop off the carboxyl group
What is the role of biotin in pyruvate carboxylation?
- lysine residue is bound to biotin, which picks up the carboxyl group
(active site 1) - the biotin transfers the carboxyl group to another molecule
(active site 2)
What is the common name for Vitamin B9
Folate/ folic acid
What are the differences in folate and folic acid
Folic acid
- high absorption
- found in fortified food/ supplements
Folate
- natural, found in food
- less efficiency absorption
What are the 3 components of folate?
- Pterin ring, PABA, glutamic acid
- humans can form all of these, but cannot join them together (therefore folate is an essential nutrient)
