thiamin, riboflavin, niacin Flashcards
what type of vitamins are thiamin, riboflavin and niacin (what letter)?
vitamin B (B1 B2 B3)
what are the general functions of B vitamins
macronutrient metabolism energy production energy release energy metabolism transfer of single carbon units
B vitamins are part of the structure of _____ that are needed for _____, which drive many reactions and pathways
co-enzymes
enzymes
what are the 5 intermediary metabolism activities that vitamins are involved in?
CHO
-glycolysis and gluconeogenesis
PRO
-protein synthesis and AA oxidation
FATS
-FA synthesis and beta oxidation
ATP GENERATION
-respiratory chain and oxidative phosphorylation
NUCLEIC ACIDS/FA/STEROIDS
-pentose phosphate pathway
what is Vit B1
thiamin
what needs to happen to thiamine in order for it to act as a coenzyme
it needs to have two phosphates added to it
study reminder
know structure of thiamine
what is the co-enzyme form of thiamin
thiamin pyrophosphate (TPP)
what are the metabolic roles of thiamin
- facilitiates energy release from foods
- central role in CHO metabolism
- oidative decarboxylation
- -> pyruvate dehydrogenase
- -> alpha-ketogluterate dehydrogenase
- -> pyruvate dehydrogenase
- transketolase reactions
- -> also req. Mg
CHO PRO and FAT all oxidize to ______, which is central in macronutrient metabolism
acetyl CoA
what deficiency is associated with BERI-BERI (“ I cant I cant”)
thiamin (B1) deficiency
what are general symptoms of thiamin deficiency
- dec fluid intake
- anorexia with weight loss
- neurological symptoms
- paralysis
- cardiovascular and respiratory
can a thiamin deficiency be easily reversed
yes, with thiamin
what was done to flour in canada that has made thiamin deficiencies rare?
fortification of flour
what are the 3 types of BERI-BERI
WET (edema)
DRY (no edema)
INFANTILE
what are symptoms of WET BERI-BERI
- cardiovascular, respiratory
- heart swelling
- pulmonary congestion
what are symptoms of DRY BERI-BERI
- CNS impairment
- alcoholics (Wernicke-Korsakoff Syndrome)
- confusion, memory loss, confabulation (clear memory of something that never happened)
what are signs of INFANTILE BERI-BERI
- brest fed infants of deficient mothers (or formula that doesnt have thiamin)
- vomiting, diarrhea, convulsions
- aphonia–crying but no sound coming out
- sudden death
- responds to thiamin quickly
what is the EFSA
European Food Safety Authority
panel on dietetic products, nutrition and allergies
which vitamin contributes to normal CHO and energy-yielding metabolism, and maintenance of normal neurological function
thiamin
what is Vit B2, and why is it called B2
riboflavin
it was the second one that was discovered
what are the coenzyme forms of riboflavin
FMN (flavin mononucleotide)
FAD (flavin adenine dinucleotide)
is riboflavin water or lipid soluble
water soluble
what are two characteristics of the appearance of riboflavin
yellow
fluorescent
what vitamin needs riboflavin to function?
why is it needed
Vit B6
riboflavin is essential for conversion of B6 to its co-enzyme form
metabolic roles of FMN and FAD
-accept and donate hydrogens
- part of flavin-dependent enzymes
- called AA oxidases
- respiratory chain/energy production
- TCA cycle
food sources for riboflavin
milk and milk products
-photolabile… need to keep out of light
liver, meat
milling of wheat results in significant losses
fortified flour in canada
riboflavin deficiency
never fatal
lesion symptoms
- cheilosis (lesions around mouth)
- magenta tongue
- angular stomatitis
- seborrheic dermatitis
also affects vit B6
what is the nutrient nutrient interaction between riboflavin and iron?
*good exam question
riboflavin deficiency can impair mobilization of iron from its storage protein (ferritin)
and
impair iron absorption
what are the two chemical structures of niacin (B3) ?
which one is the major form in the blood?
nicotinic acid
nicotinamide (major form in blood)
what are the co-enzyme forms of niacin
NAD (H) (nicotinamide adenine dinucleotide)
NADP (H)
what AA can niacin be synthesized from?
tryptophan…an essential AA!
what is the conversion of tryptophan to niacin?
60mg tryptophan = 1mg niacin
what is the units used for niacin
niacin equicalents (NE)
what do we have to take into consideration when calculating niacin intake?
protein intake
what is the beginning and end result in the Kynurenin Pathway?
tryptophan—->niacin (co enzyme forms; NAD/NADP
what two vitamins does the Kynurenine pathway need
riboflavin
Vit B6
we can replace the need for niacin in the diet of rodents, dogs and pigs, by putting _____ in the diet
tryptophan
why is it called the kynurenine pathway
because kynurenine is a key intermediate in the conversion of tryptophan to niacin (in its coenzyme form)
niacin transfers _____ during metabolic reaction
what types of reactions are these
hydrogen
oxidation/reduction
study reminder
review how and where niacin is used in: Glycolysis/gluconeogenesis TCA cycle ETC pentose phosphate pathway
during oxidation, Niacin acts as a hydrogen (acceptor/donor)
acceptor
NAD(P) –> NAD(P)H
during reduction, niacin acts as a hydrogen (acceptor/donor).
donor
NAD(P)H becomes NAD(P)
pentose phosphate pathway is an alternative route of ______metabolim
glucose
what are the 2 purposes or the pentose phosphate pathway
generate NADPH, then used for syntehsis of FA and steroids
generate ribose for synthesis of nucleic acids
what are the four D’s? (symptoms)
diarrhea
dermatitis
dementia
death
Niacin deficiency
- pellagra (rough skin)
- four D’s
study reminder
go over pellagra case study
what is hartnup’s disease
autosomal recessive disorder
-development of pellagra due to defect in absorption process for tryptophan
Niacin and the plague of corn
what is corn limiting in?
niacin is bound and unavailbe
limiting in tryptophan
this leads to pelllagra
what is the solution to the plague of corn
alkali treatment;
breaks the bond and makes niacin available
what nutrients would impact niacin status
protein
riboflavin
Vit B6
what nutrient has been used as a cholesterol lowering agent?
nicotinic acid
Niacin and CVD
unique among lipid-lowering drugs like statins as it has been shown to not only reduce LDL-cholesterol but also increase HDL-cholesterol and decrease lipoprotein (a) levels
what are some side effects of niacin treatment?
abdominal pain, rash, liver toxicity
