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IHN: Biochemistry 2 > Biotin > Flashcards

Biotin Flashcards

1
Q

biotin foods

A

ALL FOODS
liver, beef

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2
Q

food form of biotin

A

free or covalently bound to proteins like biocytin

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3
Q

small amount of biotin is produced by __ in __

A

small amount of biotin is produced by bacteria in colon

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4
Q

SMVT aka

A

shared multivitamin transporter

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5
Q

biotin transporter

A

SMVT

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6
Q

SMVT is inhibited by

A

excess biotin

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7
Q

SMVT is a

A

Na-depdent symporter

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8
Q

biotin enters cell from

A

intestinal lumen (mainly jejunum)

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9
Q

biotin is found mostly __ in __ with small amounts bound to __, __, and __

A

biotin is found mostly free in plasma with small amounts bound to albumin, globulins, and biotinidase

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10
Q

biotin uptake in __ and other cells is likely mediated by __ carrier and __

A

biotin uptake in liver and other cells is likely mediated by SMVT carrier and monocarboxylate transporter (MCT)

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11
Q

biotin is present in small amounts in

A

brain
liver
muscle

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12
Q

biotin has __ and __ functions

A

biotin has coenzyme and non coenzyme functions

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13
Q

4 coenzyme functions of biotin

A
  1. pyruvate carboxylase
  2. acetyl CoA carboxylase
  3. propionyl CoA carboxylase
  4. beta-methylcrotonyl CoA carboxylase
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14
Q

1 nonenzyme function of biotin

A

regulation of gene expression

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15
Q

the enzyme __ covalently attaches __ groups to target proteins (__ and __)

A

the enzyme holocarboxylase synthetase (HCS) covalently attaches biotin groups to target proteins (enzymes and histones)

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16
Q

HCS deficiency

A

within hours to weeks of birth
emesis, hypotonia, lethargy, metabolic ketolactic acidosis

17
Q

similar diagnosis to HCS (they are often confused)

A

biotinidase deficiency (appears after 3 months)

18
Q

2 non-coenzyme roles of biotin

A
  1. biotinylation of proteins and gene regulation
  2. cell cycle
19
Q

biotinylation of proteins and gene regulation (3)

A
  1. histones: biotinylation opens up DNA-histones
  2. over 2,000 genes depend on biotin expression
  3. non-histone proteins are also targets for biotinylation
20
Q

biotinidase function

A

recycles biotin to be used by the body

21
Q

biotin is an essential coenzyme for 5 __

A

biotin is an essential coenzyme for 5 carboxylases

22
Q

what vitamin is involved in carboxylase activity?

A

biotin

23
Q

biotin in cell cycle

A

required for progression
biotin deficiency causes cell arrest in G1 phase

24
Q

the biotin cycle

A
  1. biotin enters from diet
  2. HCS helps biotin find and bind targets (holocarboxylases)
  3. once active, holocarboxylases participate in protein, lipid, and carb metabolism
  4. once used, holocarboxylases are degraded
  5. biocytin remains after degradation
  6. biotinidase releases biotin for next round of activation
25
Q

biotin is essential in __, __, and __ metabolism

A

biotin is essential in protein, lipid, and carb metabolism

26
Q

excretion metabolites produces from __ of __
via __

A

excretion metabolites produced from oxidation of valeric acid
via urine, some in feces

27
Q

assessment of biotin status (2)

A
  1. plasma and urinary biotin
  2. urinary excretion of 3-hydroxy-isovaleric acid
28
Q

is biotin deficiency common?

A

no, very rare but lethal if untreated

29
Q

groups at risk for deficiency

A

alcohol addiction
diets high in raw eggs
genetic mutations (biotinidase)

30
Q

groups at risk for deficiency

A

alcohol addiction
diets high in raw eggs
genetic mutations (biotinidase)

31
Q

biotin deficiency symptoms

A

neurologic: lethargy, depression, hallucinations
skin abnormalities: dermatitis around eyes, mouth, and eyes

32
Q

how to treat biotin deficiency

A

free biotin daily

33
Q

all biotin are attached to a

A

lysine

34
Q

biotinidase is present

A

everywhere!

35
Q

SMVT requires what to transport biotin into cell

A

Na

36
Q

biotin cycle: HCS binds to __ and biotinylates them making other enzymes biologically active

A

biotin cycle: HCS binds to histones and biotinylates them making other enzymes biologically active

37
Q

biotin is mainly secreted as an __ product

A

biotin is mainly secreted as an oxidized product

IHN: Biochemistry 2 (38 decks)

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