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HUNT241 > Nutrition Lecture 9: Riboflavin > Flashcards

Nutrition Lecture 9: Riboflavin Flashcards

1
Q

What are rich sources of riboflavin?

A

Main source = dairy products
Fortified sources: weet-bix, soy milk

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2
Q

What is the structure of riboflavin?

A

Ribose sugar and Flavin structure

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3
Q

What does riboflavin look like?

A

A yellow-orange crystalline solid

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4
Q

What is riboflavin rapidly inactivated by?

A

UV and visible light

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5
Q

What is the solubility of riboflavin?

A

Poor solubility in water compared to other B-vitamins

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6
Q

What is the bioavailability of riboflavin?

A

High - 95% absorbed

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7
Q

When does riboflavin absorption decline?

A

High doses > 27 mg

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8
Q

Where is most riboflavin absorbed?

A

In proximal small intestine

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9
Q

How is riboflavin absorbed into and out of enterocytes?

A

via riboflavin vitamin transporters (RFVT)

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10
Q

How are high doses of riboflavin absorbed?

A

by passive diffusion

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11
Q

How is riboflavin transported?

A

On proteins - primarily albumin

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12
Q

Where is riboflavin stored?

A

Stored in only small amounts in the liver, heart and kidney - enough for 2-6 weeks

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13
Q

What is the main function of riboflavin?

A

An integral component of flavocoenzymes

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14
Q

What are flavocoenzymes?

A

a group of enzymes that contain flavin cofactors derived from riboflavin (vitamin B2)

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15
Q

What are the flavocoenzymes that riboflavin are part of? (2)

A

FMN and FAD

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16
Q

What does FMN stand for?

A

Flavin mononucleotide

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17
Q

What does FAD stand for?

A

Flavin adenine dinucleotide

18
Q

What is the more common flavocoenzyme that riboflavin is converted into?

A

FMN = 60-90% of riboflavin in cells

19
Q

What is the less common flavocoenzyme that riboflavin is converted into?

A

FAD = 5-20% of riboflavin in cells

20
Q

What is the structure of Flavin mononucleotide (FMN)?

A

Riboflavin with an added phosphate group

21
Q

What is the structure of Flavin adenine dinucleotide?

A

Riboflavin with a phosphate group (FMN) and an AMP

22
Q

What is an AMP?

A

Adenosine and a monophosphate

23
Q

What are the three major roles of FMN and FAD?

A
  1. Redox reactions
  2. Antioxidant
  3. Metabolism of B-vitamins
24
Q

What is OIL RIG?

A

Oxidation is Loss
Reduction is Gain
- of electrons

25
Q

Which flavocoenzyme is part of the ETC?

A

FMN

26
Q

What part of the ETC is FMN part of?

A

Complex 1 - it is able to take on board the high energy electrons from the NADH, 4 hydrogen ions are being pumped into the intermembrane space

27
Q

FMN is also important for some co-enzymes that metabolise…

A

drugs and toxins in the body

28
Q

What do antioxidants protect the body from?

A

Free radicals - molecules with an unpaired electron so highly unstable and reactive

29
Q

What do free radicals damage?

A

DNA, proteins and lipids

30
Q

What are two FAD-dependent enzymes?

A
  1. Glutathione reductase
  2. Xanthine oxidase
31
Q

What is the glutathione peroxidase assay?

A

test used to measure the activity of the enzyme glutathione peroxidase (GPx) in biological samples

32
Q

What B vitamins does Riboflavin help metabolise?

A

Folate, B6 and niacin

33
Q

How is riboflavin involved in folate metabolism?

A

MTHFR is an FAD-dependent enzyme which maintains the specific folate co-enzyme required to form methionine from homocysteine

34
Q

How is riboflavin involved in Vitamin B6 metabolism?

A

Conversion of most naturally available B6 to its coenzyme form, requires the FMN dependent enzyme PPO

35
Q

How is riboflavin involved in niacin metabolism?

A

Synthesis of niacin containing coenzymes, NAD and NADP requires a FAD-dependent enyme

36
Q

What are symptoms of riboflavin deficiency?

A
  • Redness and swelling of mouth and throat
  • Cracks or sores on mouth
  • Inflammation of tongue
  • Dermatitis
37
Q

What are the risk factors for riboflavin deficiency?

A
  • Alcoholism
  • No dairy intake
  • Poorly controlled hypothyroidism
  • Very physically active
38
Q

What is the EAR for riboflavin?

A

Men = 1.1mg/day
Women = 0.9mg/day

39
Q

What is the RDI for riboflavin?

A

Men = 1.3mg/day
Women = 1.1mg/day

40
Q

What is the upper level of riboflavin intake?

A

No upper level of intake set

HUNT241 (22 decks)

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