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IHN: Biochemistry 2 > Riboflavin (B2) > Flashcards

Riboflavin (B2) Flashcards

1
Q

riboflavin is not an __, it does not have a __ function

A

riboflavin is not an active molecule, it does not have a biological function

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2
Q

riboflavin is a precursor of __ and __

A

riboflavin is a precursor of FMN and FAD

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3
Q

riboflavin in the form of __ is a __ in many rxns

A

riboflavin in the form of FAD is a coenzyme in many rxns

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4
Q

most enzymes use __ (75%) rather than __ (25%) and bind the cofactor covalently

A

most enzymes use FAD (75%) rather than FMN (25%) and bind the cofactor covalently

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5
Q

flavin groups transfer __ or __

A

flavin groups transfer electrons or protons

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6
Q

most flavin in our body is bound to

A

oxidoreductase enzymes

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7
Q

more than 90% of flavin-dependent enzymes are __
most use __ rather than __

A

more than 90% of flavin-dependent enzymes are oxidoreductases
most use FAD rather than FMN

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8
Q

food form of riboflavin

A

dairy
grains
meat, eggs
vegetables
high protein!

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9
Q

riboflavin is unstable with __ and __

A

riboflavin is unstable with light exposure and alkaline conditions (baking soda)

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10
Q

transporter of riboflavin

A

RFVT 1, 2, and 3

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11
Q

__ transporters uptake and excrete riboflavin

A

3 RFVT transporters uptake and excrete riboflavin

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12
Q

circulation of riboflavin is mostly attached to __ (mainly __)

A

circulation of riboflavin is mostly attached to proteins (mainly albumin)

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13
Q

dietary form

A

flavoprotein

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14
Q

which transporter has high affinity for riboflavin?

A

RFVT3

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15
Q

RFVT 1 and 2 __ riboflavin
RFVT 3 __ riboflavin to __

A

RFVT 1 and 2 uptake riboflavin
RFVT 3 send riboflavin to urine

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16
Q

immunoglobulins vs albumin
which has higher affinity?
which is main transporter?

A

immunoglobulins have higher affinity
BUT there is more albumin, so it is the main transporter

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17
Q

absorption, transport, and excretion

A
  1. dietary flavoprotein –> FAD (proteases)
  2. FAD –> FMN (pyrophosphatase)
  3. FMN –> riboflavin (phosphatase)
  4. RFVT3 on apical surface brings free riboflavin into cell
  5. free riboflavin enters blood through RFVT1+2 OR riboflavin in cell becomes FAD/FMN and is used by cell
  6. in portal blood, riboflavin binds immunoglobulins and albumin
  7. RBC uptake riboflavin
  8. remaining to liver and other cells
18
Q

main riboflavin transporter?

A

albumin

19
Q

95% of flavin intake is absorbed, at this point, plasma levels __ and absorption __

A

95% of flavin intake is absorbed, at this point, plasma levels peak and absorption plateaues

20
Q

over-excess riboflavin excreted via

A

feces

21
Q

4 factors that interfere with digestion and absorption of flavins

A
  1. alcohol consumption
  2. metals: copper, zinc, iron
  3. caffeine
  4. vitamins, nicotinamide, ascorbic acid
22
Q

how does alcohol interrupt flavins

A

destroys vitamin transporters

23
Q

metabolism of riboflavin in tissue (3 steps)

A

riboflavin –> FMN –> FAD

24
Q

__ hormones impact expression and action of riboflavin enzymes

A

thyroid hormones impact expression and action of riboflavin enzymes

25
Q

RFT1

A

expressed mostly in placenta, intestine, kidney
low transport activity

26
Q

RFT2

A

expressed in most tissues, highest in brain, salivary glands, intestine, and colon

27
Q

RFT2 is highly active with (3)

A

riboflavin, FAD, FMN

28
Q

RFT2 is inhibited by

A

chlorpromazine (anti-psychotic drug)

29
Q

RFT3

A

expressed in intestine, prostate, testis, stomach, pancreas

30
Q

RFT3 is highly homogenous with

A

RFT1

31
Q

riboflavin is found in most tissues mainly

A

liver kidneys and heart

32
Q

riboflavin is secreted in

A

milk

33
Q

almost all riboflavin in tissues is __

A

almost all riboflavin in tissues is enzyme bound

34
Q

body stores enough riboflavin for

A

2-6 weeks

35
Q

unbound flavins are rapidly __ to __ riboflavin which __ from cell

A

unbound flavins are rapidly hydrolyzed to free riboflavin which diffuses from cell

36
Q

intracellular phosphorylation of riboflavin is a way to

A

trap riboflavin and maintain homeostasis

37
Q

FMN and FAD are used in 2 types of rxns

A
  1. REDOX
  2. lipid and drug metabolism
38
Q

FAD has a role in __ to donate __

A

FAD has a role in ETC to donate electrons

39
Q

assessment of flavin status

A

erythrocyte glutathione reductase activity coeffiency (EGRAC) ratio

40
Q

why use glutathione reductase to measure flavin activity

A

it uses riboflavin as a cofactor

41
Q

groups at risk for riboflavin deficiency

A
  1. schoolchildren: low intake of milk and meat
  2. elderly
  3. athletes: vigorous exercise

IHN: Biochemistry 2 (38 decks)

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