Riboflavin (B2)

Question 1

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

Answer 1

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

Question 2

riboflavin is a precursor of __ and __

Answer 2

riboflavin is a precursor of FMN and FAD

Question 3

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

Answer 3

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

Question 4

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

Answer 4

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

Question 5

flavin groups transfer __ or __

Answer 5

flavin groups transfer electrons or protons

Question 6

most flavin in our body is bound to

Answer 6

oxidoreductase enzymes

Question 7

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

Answer 7

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

Question 8

food form of riboflavin

Answer 8

dairy
grains
meat, eggs
vegetables
high protein!

Question 9

riboflavin is unstable with __ and __

Answer 9

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

Question 10

transporter of riboflavin

Answer 10

RFVT 1, 2, and 3

Question 11

__ transporters uptake and excrete riboflavin

Answer 11

3 RFVT transporters uptake and excrete riboflavin

Question 12

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

Answer 12

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

Question 13

dietary form

Answer 13

flavoprotein

Question 14

which transporter has high affinity for riboflavin?

Answer 14

RFVT3

Question 15

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

Answer 15

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

Question 16

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

Answer 16

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

Question 17

absorption, transport, and excretion

Answer 17

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

Question 18

main riboflavin transporter?

Answer 18

albumin

Question 19

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

Answer 19

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

Question 20

over-excess riboflavin excreted via

Answer 20

feces

Question 21

4 factors that interfere with digestion and absorption of flavins

Answer 21

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

Question 22

how does alcohol interrupt flavins

Answer 22

destroys vitamin transporters

Question 23

metabolism of riboflavin in tissue (3 steps)

Answer 23

riboflavin –> FMN –> FAD

Question 24

__ hormones impact expression and action of riboflavin enzymes

Answer 24

thyroid hormones impact expression and action of riboflavin enzymes

Question 25

RFT1

Answer 25

expressed mostly in placenta, intestine, kidney low transport activity

Question 26

RFT2

Answer 26

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

Question 27

RFT2 is highly active with (3)

Answer 27

riboflavin, FAD, FMN

Question 28

RFT2 is inhibited by

Answer 28

chlorpromazine (anti-psychotic drug)

Question 29

RFT3

Answer 29

expressed in intestine, prostate, testis, stomach, pancreas

Question 30

RFT3 is highly homogenous with

Answer 30

RFT1

Question 31

riboflavin is found in most tissues mainly

Answer 31

liver kidneys and heart

Question 32

riboflavin is secreted in

Answer 32

milk

Question 33

almost all riboflavin in tissues is __

Answer 33

almost all riboflavin in tissues is **enzyme bound**

Question 34

body stores enough riboflavin for

Answer 34

2-6 weeks

Question 35

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

Answer 35

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

Question 36

intracellular phosphorylation of riboflavin is a way to

Answer 36

trap riboflavin and maintain homeostasis

Question 37

FMN and FAD are used in 2 types of rxns

Answer 37

1. REDOX 2. lipid and drug metabolism

Question 38

FAD has a role in __ to donate __

Answer 38

FAD has a role in **ETC** to donate **electrons**

Question 39

assessment of flavin status

Answer 39

erythrocyte glutathione reductase activity coeffiency (EGRAC) ratio

Question 40

why use glutathione reductase to measure flavin activity

Answer 40

it uses riboflavin as a cofactor

Question 41

groups at risk for riboflavin deficiency

Answer 41

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