Lecture 9 - Riboflavin Flashcards
what is the main food source of riboflavin for most people
dairy products
how much riboflavin would you get from one cup of blue milk
0.7mg (around 60% of RDI)
common sources of riboflavin
egg, dairy products, fortified milk, weetbix and other cereals
what are the two component molecules of riboflavin
ribose sugar and ‘flavin’
what are the characteristics of riboflavin
yellow - orange crystalline solid
fluorescent under UV light
what is the solubility of riboflavin (B2) compared to other B vitamins
poor solubility in water compared to other B vitamins
but you would still lose a lot if you were to boil it
what rapidly inactivates riboflavin (B2)
UV and visible light
if riboflavin is bound to proteins in food what happens
removed by HCL and proteases
where is most riboflavin absorbed
in the proximal small intestine
riboflavin is absorbed into and out of enterocyte via what
riboflavin vitamin transporters (RFVT)
at high doses of riboflavin what type of absorption occurs
passive diffusion
what is the bioavailability of riboflavin
high, ~95% absorbed
how is riboflavin typically transported
on proteins (primarily albumin)
where is riboflavin found in the body
widely distributed in body tissues
how well and where is riboflavin stored
stored only in small amounts in the liver, heart and kidney
how long will storage of riboflavin last
enough for 2-6 weeks
what is a function of riboflavin
intergral component of flavocoenzymes
what are two examples of flavocoenzymes
- flavin mononucelotide (FMN)
- flavin adenine dinucleotide (FAD)
what are the three major roles of FMN and FAD
- oxidation-reducation (redox) reactions
- antioxidant functions
- metabolism of several B vitamins (including folate, vitamin B6 and niacin)
flavocoenzymes are involved in redox reactions, especially in what pathways
pathways metabolising carbohydrates, lipids and proteins
what is flavin mononucelotide (FMN) part of
the electron transport chain (specifically complex 1)
what is FMN’s role in the electron transport chain
able to take on board high energy electrons from NADH and transfer them to the iron-sulfur complex which then takes them to ubiquione
what do antioxidants protect the body from
protect the body from free radicals
what are free radicals
unpaired electrons so highly unstable
free radicals (including reactive oxygen species ) damage what
damage DNA, proteins and lipids = causing multiple inflammatory diseases
glutathione reductase is a what dependent enzymes and what cycle is it apart of
FAD-dependent enzymes in the glutathione redox cycle
what does glutathione reductase do in the glutathione redox cycle
maintains supply of reduced glutathione which counteracts reactive oxygen species
xanthine oxidase is a what dependent enzyme and what does it catalyse
FAD-dependent enzyme and catalyses the oxidation of hypoxanthine and xanthine to uric acid
uric acid is one of the most effective what
one of the most effective water soluble antioxidants in blood
what is reduced glutathione and what is this able to do
2GSH = this is available and ready to react with different sorts of peroxides
what converts peroxides and reduced glutathione to oxidised glutathione and water
glutathione peroxidase
flavocoenzymes are required by proteins for the metabolism of what B vitamins
metabolism of folate, vitamin B6 and niacin
5,10-methylTHF reductase is a what dependent enzyme and what is its role
FAD-dependent enzymes with important role in maintaining the specific folate coenzyme required to form methionine from homocysteine
conversion of most naturally available vitamin B6 to its co-enzyme form (what is this and what does it reqiure)
co enzyme form = pyridoxal 5-phosphate (PLP)
requires the FMN dependent enzyme pyridoxine 5-phosphate oxidase (PPO)
synthesis of the niacin containing coenzymes (NAD and NADP) from the amino acid tryptophan requires what
a FAD dependent enzyme
If there isn’t enough riboflavin what might happen to the levels of 5-methyl tetrahydrofolate?
have problems making enough 5-methyl THF
If there isn’t enough riboflavin what would happen to the levels of homocysteine?
levels will increase because not enough 5-methyl THF to keep convert homocysteine to methionine
If there isn’t enough riboflavin what major functional pathway could be affected due to increased levels of homocysteine
DNA methylation
what are symptoms of deficiency of riboflavin
- redness and swelling of the lining of mouth and throat
- cracks or sores at corners of the moth (angular stomatitis)
- inflammation and redness of the tongue (magenta tongue)
- moist, scaly skin inflammation
what may also you observe in riboflavin deficiency
formation of blood vessels in the clear covering of the eye (vascularisation of the cornea)
decreased RBC count with cells of normal size and normal levels of haemoglobin = this is hard to detecrt
risk factors for riboflavin deficiency
alcohol dependency
vegans, lactose intolerance, limited access
poorly controlled hypothyroidism and adrenal insufficiency
very active physically
what is the RDI for riboflavin for adult men
1.1mg/day
what is the RDI for riboflavin for adult women
0.9mg/day
what is the upper limit of riboflavin
no upper limit set
