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HUNT241 > Lecture 9- Riboflavin > Flashcards

Lecture 9- Riboflavin Flashcards

1
Q

what is the main food source of riboflavin for most people

A

dairy products

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2
Q

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

A

0.7mg (around 60% of RDI)

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3
Q

common sources of riboflavin

A

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

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4
Q

what are the two component molecules of riboflavin

A

ribose sugar and ‘flavin’

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5
Q

what are the characteristics of riboflavin

A

yellow - orange crystalline solid

fluorescent under UV light

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6
Q

what is the solubility of riboflavin (B2) compared to other B vitamins

A

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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7
Q

what rapidly inactivates riboflavin (B2)

A

UV and visible light

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8
Q

if riboflavin is bound to proteins in food what happens

A

removed by HCL and proteases

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9
Q

where is most riboflavin absorbed

A

in the proximal small intestine

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10
Q

riboflavin is absorbed into and out of enterocyte via what

A

riboflavin vitamin transporters (RFVT)

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11
Q

at high doses of riboflavin what type of absorption occurs

A

passive diffusion

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12
Q

what is the bioavailability of riboflavin

A

high, ~95% absorbed

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13
Q

how is riboflavin typically transported

A

on proteins (primarily albumin)

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14
Q

where is riboflavin found in the body

A

widely distributed in body tissues

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15
Q

how well and where is riboflavin stored

A

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

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16
Q

how long will storage of riboflavin last

A

enough for 2-6 weeks

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17
Q

what is a function of riboflavin

A

intergral component of flavocoenzymes

18
Q

what are two examples of flavocoenzymes

A

flavin mononucelotide (FMN)
flavin adenine dinucleotide (FAD)

19
Q

what are the three major roles of FMN and FAD

A

oxidation-reducation (redox) reactions

antioxidant functions

metabolism of several B vitamins (including folate, vitamin B6 and niacin)

20
Q

flavocoenzymes are involved in redox reactions, especially in what pathways

A

pathways metabolising carbohydrates, lipids and proteins

21
Q

what is flavin mononucelotide (FMN) part of

A

the electron transport chain (specifically complex 1)

22
Q

what is FMN’s role in the electron transport chain

A

able to take on board high energy electrons from NADH and transfer them to the iron-sulfur complex which then takes them to ubiquione

23
Q

what do antioxidants protect the body from

A

protect the body from free radicals

24
Q

what are free radicals

A

unpaired electrons so highly unstable

25
Q

free radicals (including reactive oxygen species ) damage what

A

damage DNA, proteins and lipids = causing multiple inflammatory diseases

26
Q

glutathione reductase is a what dependent enzymes and what cycle is it apart of

A

FAD-dependent enzymes in the glutathione redox cycle

27
Q

what does glutathione reductase do in the glutathione redox cycle

A

maintains supply of reduced glutathione which counteracts reactive oxygen species

28
Q

xanthine oxidase is a what dependent enzyme and what does it catalyse

A

FAD-dependent enzyme and catalyses the oxidation of hypoxanthine and xanthine to uric acid

29
Q

uric acid is one of the most effective what

A

one of the most effective water soluble antioxidants in blood

30
Q

what is reduced glutathione and what is this able to do

A

2GSH = this is available and ready to react with different sorts of peroxides

31
Q

what converts peroxides and reduced glutathione to oxidised glutathione and water

A

glutathione peroxidase

32
Q

flavocoenzymes are required by proteins for the metabolism of what B vitamins

A

metabolism of folate, vitamin B6 and niacin

33
Q

5,10-methylTHF reductase is a what dependent enzyme and what is its role

A

FAD-dependent enzymes with important role in maintaining the specific folate coenzyme required to form methionine from homocysteine

34
Q

conversion of most naturally available vitamin B6 to its co-enzyme form (what is this and what does it reqiure)

A

co enzyme form = pyridoxal 5-phosphate (PLP)

requires the FMN dependent enzyme pyridoxine 5-phosphate oxidase (PPO)

35
Q

synthesis of the niacin containing coenzymes (NAD and NADP) from the amino acid tryptophan requires what

A

a FAD dependent enzyme

36
Q

If there isn’t enough riboflavin what might happen to the levels of 5-methyl tetrahydrofolate?

A

have problems making enough 5-methyl THF

37
Q

If there isn’t enough riboflavin what would happen to the levels of homocysteine?

A

levels will increase because not enough 5-methyl THF to keep convert homocysteine to methionine

38
Q

If there isn’t enough riboflavin what major functional pathway could be affected due to increased levels of homocysteine

A

DNA methylation

39
Q

what are symptoms of deficiency of riboflavin

A

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

40
Q

what may also you observe in riboflavin deficiency

A

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

41
Q

risk factors for riboflavin deficiency

A

alcohol dependency

vegans, lactose intolerance, limited access

poorly controlled hypothyroidism and adrenal insufficiency

very active physically

42
Q

what is the upper limit of riboflavin

A

no upper limit set

HUNT241 (19 decks)

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