by bnbond


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Best sources of Bit B1
Meats and Grains
Absorbtion of Vit B1 at the brush border
sodium active transport
Vit b1 absorbtion at the basolateral memrane
active proton transport (an antiport)
Functions and mechanisms of action of Vit B1?
*energy transformation (plays a part in E1 mechanishm--pyruvate dehydrogenase and alpha keto glut dehydrogenase)
*pentose phosphate pathway (transktolase)
*membrane and nerve conduction (thiamin activates chloride ion transport in nerve membranes...also may regulate sodium channels in nerve impules)
How is thiamin excreted?
in the urine-intact or metabolized
Def. of Vit B1 causes....
*beri beri and wernicke-Korsakoff syndrome

(remember that alcohol inhibits basolateral absorbtion)
Toxicity of V B1
NONE
What are the best sources of V-B2
animal products
What mechanism/enzymes require Riboflavin/B2
*redox reaction
*succinyl dehydrogenase (ETC complex 2)
*pyruvate dehydrogenase (E3)
*alpha ketoglut dehydrogenase
*beta oxidation
*xanhine oxidase (uric aced synthesis)
*peridoxine phosphate oxidase
*NO synthase
*glutathione reductase
Metabolism of Riboflavin/B2
Its metabolites are excreted in the urine...urine color change from B complex is a breakdown product of riboflavin
Def. of V-B2
Ariboflavinosis
Toxicity and upper limits of B2
None and None
clinical uses (large doses)
Migraine headaches
Three types of B6
pyridoxine, pyridoxal, and pyridoxamine
what has to happen before V-B6 is absorbed
dephosphorylated
Which B-6 enzyme(s) can be oxidized to pyridoxal?
pyridoxine and pyridoxanine
How is B6 taken up by the liver
passive diffusion
The unphosphorylated form of B6 can be taken up by what>?
RBCs
Muscles store about ---% of B6 bound to -----------?
75-80% bound to glycogen phosphate
Functions of B6
*intermediate to the oxaloacetate-alpha ketoglut, asp-glutamate, AST-ALT reactions
*decarboxylation reactions
*transulfhydration (the other way to get rid of cysteine--which is conditionally essential on methionine)
*cleavage (of serine hydroxymethyltransferase)
*racemase (interconverts D and L configurations---prop CoA to Suc CoA {know this pathway})
*heme synthesis (rate limiting step making heme requires B6)
*carnitine synthesis (made in liver)
*taurine synthesis (made in liver)
*cofactor for glycogen phosphorylase in muscle
*steroid hormone modulation (bings to steroid hormone receptor site, diminishes teh effect of steroids, b6 decreases cancer in these types)
Excretion of B6
its metabolite (which is useless) is excreted in urine
Def. of B6
fatigue, seizures, anemia,
Toxicity of b6
doses greater than 500 mg/day can cause peripheral neuropathies (demyelinates, degeneration of sensory fibers in peripheral nerves and dorsal root ganglia)
two types of V-B3 (niacin)
nicotinic acid vs. nicotinamide
best sources of B3
meat, fish, chicken
Where is NAD sythesized?
May be synthesized in the liver from Tryptophan. But you dont make enough, so you mush eat it.
Kynourian pathway?
At low concentrations, niacin it absorbed how?
Taken up by sodium dependent (carrier mediated?) facilitated diffusion.
At high concentration, niacin is absorbed how?
Passive diffusion
How does niacin move into the cell?
Simple diffusion.
b2 interactions with others?
may decrease the synthesis of coenxyme form of B6 and niacin (NAD)
Transport of Niacin?
1/3 of all nicotinic acid in plasma bound is bound to protein (mainly albumin)
-nicotinamide and nicotinic acid enter blood cells by simple diffusion
Storage of B3
-nicotinamide serves as a precursor for NAD and is synthesized in all tissues.
-small amounts of NAD are stored in the liver not bound to enymes
Functions of B3
-many enzymes require NAD and NADP as a coenzyme
--oidation reactions (glycolosis, oidative decarboxylation of pyruvate, oxid of acetyl CoA via Krebs cycle, beta oxidation of fatty acids, malate/pyruvate shuttle)
--NADPH generation used in...(fatty acid synthesis, steroid hormone synthesis, and glutathione synthesis)
glycohydrolase role and B3
NAD and NADP can be degraded by glycohydrolase
Excretion of B3
variety of metabolites are excreted in the urine
Def. of Niacin
Causes pellegra (4 D's--dermatisis, diarrhea, dementia, and death)
Toxicity of Niacin
--may cause heart burn, nausea, and gout.
Clinical uses of niacin
--large does of nicotinic acid are used to treat hypercholesterolemia
Best source of pantothenic acid?
in most plants and animal food sources
Absorbion of Pantothenic acid
--mainly in jejunum through passive diffusion
--50% of it is absorbed
Storage of Pantothenic acid
-found free in bloom plasma/serum
-highler inercellular concentration than extracellular concentration
Function of Pantothenic acid?
used in the synthesis of CoA

-TCA: pyruvate-->acetyle coA (pyrucvate dehydrogenase)
-TCA: alpha-ketoglutarate-->succinyl CoA (alpha-ketoglut. dehydrogenase)
-FA synthesis: acetyl CoA + CoA + CO2-->malonyl CoA--> malonyl CoA (acetly CoA carboxylase)
Metabolism and Excretion of Pantothenic acid
Excreted intact in the urine.
Def. of pantothenic acid
"burning feet syndrome"--characterized by numbness and burning sensation in the feet.
Toxicity
None reported
Sources of Biotin
-mainly in meats
-produced by intestinal bacteria in the large intestines
What happens to biotin before absorbtion?
biocytin must be hydrolyzed to release free biotin and lysine (via biotinidase). Biocytin is found on the intestinal brush border.
How is biotin absorbed?
across the brush border of the SI and the colonocytes via carrier mediated and sodium dependent transport
-crosses basolateral membrane via carrier mediated transport
-bacteria synthesized biotin is absorbed in the proximal and mid-transverse colon.
How is biotin transported
-unbound biotin is typically found in plasma, lesser amounts bound to albumin
-uptake of biotin into tissue is via active sodium dependent carrier transport.
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