riboflavin Flashcards

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1
Q

name some properties of riboflavin

A

Water soluble, - So leaches out when cook in water and lost

heat stable, -

light sensitive- so light exposure destroys riboflavin

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2
Q

what does FMN stand for and what is it

A

Flavin MonoNucleotide = Cofactor of enzymatic reactions – redox reactions

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3
Q

what vitamin is riboflavin

A

B2

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4
Q

what are the coenzymes called that are formed from dietary riboflavin

A

flavin mononucleotide (FMN) and
flavin adenine dinucleotide (FAD).

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5
Q

what are the cofactors formed from dietary riboflavin involved in

A

a variety of diverse redox reactions in body systems.

Its involved in energy gen

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6
Q

what food sources is riboflavin principally derived from, and what form is the riboflavin found in within these foods

A

derived principally from animal products (milk and dairy products) and, therefore, mostly in FAD or FMN form, attached to protein.

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7
Q

FAD & FMN cleaved by what, and where

A

phosphatases in intestine.

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8
Q

absorption of riboflavin is of what type of riboflavin and what process does it go through for absorption

A

Absorption is of free riboflavin (found in significant amounts only in milk and eggs) by active transport (small intestine; saturation ≈ 30 mg).

Flavin cnat be absorbed in the structure its in in the food source or body

Only free riboflavin form can be absorbed

Absorption is in small intestine at 30mg, Any other saturation is lost

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9
Q

what happens to riboflavin in the body

A

riboflavin is phosphorylated to FMN by flavokinase, then attached to adenine to form FAD by FAD synthetase (blood principally riboflavin; albumin transport).

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10
Q

whats the EAR for riboflavin in men and in females

A

0.9 mg/day for females; 1 mg/day for males

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11
Q

what is the RNI for riboflavin in men and females

A

1.1 mg/day for females;
1.3 mg/day for males (LRNI 0.8 mg/day).

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12
Q

explain the biochemical measurement of riboflavin

A

urinary excretion of riboflavin

erythrocyte riboflavin (take blood sample and look at how much the red blood cells contain)

EGRAC; erythrocyte glutathione reductase activity coefficent

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13
Q

write the EGRAC - erythrocyte glutathione reductase activity coefficent- reaction

A

GSSG + NADPH —FAD–> 2GSH + NADP

GSSG – glutathione

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14
Q

explain the EGRAC reaction process (erythrocyte glutathione reductase activity coefficent)

A

stimulated by incubation with known quantity of FAD. The ratio of stimulated to unstimulated activity = activation coefficient, which indicates FAD saturation of the enzyme (reflection of riboflavin intake).

EGRAC value of 1 = saturation of enzyme by riboflavin

≥ 1.3 = riboflavin deficiency

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15
Q

what are problems with the EGRAC reaction

A

negative nitrogen balance –

significant amount of flavoproteins in lean tissue.

Tissue breakdown = released

increased urinary excretion of riboflavin and saturation of glutathione reductase

Its not a reliable measurement or riboflavin value

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16
Q

food sources of riboflavin

A

milk, yoghurt, cheeses

mushrooms, dark green leafy vegetables

offal (liver)

wholegrains

almonds

salmon, mackerel,herring, sardines

Often associated with wholegrains, animal products, and specific plant products

17
Q

what happens to riboflavin content when cereal products refined

A

riboflavin content is reduced. So its usually fortified in these foods

18
Q

what does riboflavin deficiency look like

A

cheilosis

angular stomatitis (sores at side of mouth, easily infected)

seborrhoeic dermatitis(inflammation of skin)

purple fissured tongue + glossitis

vascularised cornea (lots fine blood vessels in eye)

Photophobia (react adversely to bright light)

peripheral neuropathy (inflamartion of sensory nerve ending, giving tingling or burning sensation, leading to numbness)

Not common clinical deficiency state

19
Q

what is riboflavin deficiency known as

A

ariboflavinosis

20
Q

who is highly at risk of riboflavin deficiency

A

elderly

21
Q

intakes below the LRNI where found in what gender and age groups and why

A

female 11 to 18 years of age (due to puberty) and women aged 19 to 64 years. (due to reproductive age)

22
Q

adequate riboflavin intake is required in the synthesis of what

A

of niacin from tryptophan

23
Q

what causes increased riboflavin requirements

A

phototherapy for hyperbilirubinaemia as riboflavin is light sensitive (445-450 nm).

Premature neonate particularly susceptible (neonatal jaundice; under-developed enteral absorptive capacity).