Lecture 9- Riboflavin Flashcards by Harriet Lynch

what is the main food source of riboflavin for most people

dairy products

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how much riboflavin would you get from one cup of blue milk

0.7mg (around 60% of RDI)

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common sources of riboflavin

egg, dairy products, fortified milk, weetbix and other cereals

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what are the two component molecules of riboflavin

ribose sugar and ‘flavin’

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what are the characteristics of riboflavin

yellow - orange crystalline solid

fluorescent under UV light

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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

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what rapidly inactivates riboflavin (B2)

UV and visible light

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if riboflavin is bound to proteins in food what happens

removed by HCL and proteases

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where is most riboflavin absorbed

in the proximal small intestine

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riboflavin is absorbed into and out of enterocyte via what

riboflavin vitamin transporters (RFVT)

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at high doses of riboflavin what type of absorption occurs

passive diffusion

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what is the bioavailability of riboflavin

high, ~95% absorbed

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how is riboflavin typically transported

on proteins (primarily albumin)

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where is riboflavin found in the body

widely distributed in body tissues

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how well and where is riboflavin stored

stored only in small amounts in the liver, heart and kidney

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how long will storage of riboflavin last

enough for 2-6 weeks

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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 upper limit of riboflavin

no upper limit set