riboflavin

Question 1

name some properties of riboflavin

Answer 1

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

heat stable, -

light sensitive- so light exposure destroys riboflavin

Question 2

what does FMN stand for and what is it

Answer 2

Flavin MonoNucleotide = Cofactor of enzymatic reactions – redox reactions

Question 3

what vitamin is riboflavin

Answer 3

B2

Question 4

what are the coenzymes called that are formed from dietary riboflavin

Answer 4

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

Question 5

what are the cofactors formed from dietary riboflavin involved in

Answer 5

a variety of diverse redox reactions in body systems.

Its involved in energy gen

Question 6

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

Answer 6

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

Question 7

FAD & FMN cleaved by what, and where

Answer 7

phosphatases in intestine.

Question 8

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

Answer 8

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

Question 9

what happens to riboflavin in the body

Answer 9

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

Question 10

whats the EAR for riboflavin in men and in females

Answer 10

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

Question 11

what is the RNI for riboflavin in men and females

Answer 11

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

Question 12

explain the biochemical measurement of riboflavin

Answer 12

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

Question 13

write the EGRAC - erythrocyte glutathione reductase activity coefficent- reaction

Answer 13

GSSG + NADPH —FAD–> 2GSH + NADP

GSSG – glutathione

Question 14

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

Answer 14

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

Question 15

what are problems with the EGRAC reaction

Answer 15

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

Question 16

food sources of riboflavin

Answer 16

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

Question 17

what happens to riboflavin content when cereal products refined

Answer 17

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

Question 18

what does riboflavin deficiency look like

Answer 18

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

Question 19

what is riboflavin deficiency known as

Answer 19

ariboflavinosis

Question 20

who is highly at risk of riboflavin deficiency

Answer 20

elderly

Question 21

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

Answer 21

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

Question 22

adequate riboflavin intake is required in the synthesis of what

Answer 22

of niacin from tryptophan

Question 23

what causes increased riboflavin requirements

Answer 23

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

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