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HUNT 241 > 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

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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
  1. oxidation-reducation (redox) reactions
  2. antioxidant functions
  3. 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 RDI for riboflavin for adult men

A

1.1mg/day

43
Q

what is the RDI for riboflavin for adult women

A

0.9mg/day

44
Q

what is the upper limit of riboflavin

A

no upper limit set

HUNT 241 (19 decks)

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