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IHN: Biochemistry 2 > TBL: choline > Flashcards

TBL: choline Flashcards

1
Q

the gene for the enzyme that catalyzes choline biosynthesis is induced by

A

estrogen

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2
Q

choline 3 functions

A
  1. source of methyl groups for SAM
  2. acetylcholine
  3. part of main phospholipid in membranes
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3
Q

dietary sources of choline

A

eggs
liver
wheat germ (membrane rich components)

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4
Q

betaine is a

A

choline metabolite

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5
Q

betaine can’t be converted to __ but can be used as a __, sparing some __

A

betaine can’t be converted to choline but can be used as a methyl donor, sparing some choline requirements

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6
Q

good source of betaine

A

beets

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7
Q

is human breast milk rich in choline?

A

YES

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8
Q

__ degrade choline to make __ and __ before it can be absorbed

A

gut bacteria degrade choline to make betaine and methylamines before it can be absorbed

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9
Q

free choline that survives the gut bacteria is absorbed by the __ by __ transport

A

free choline that survives the gut bacteria is absorbed by the intestine by carrier-mediated transport

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10
Q

what 2 items contain enzymes that hydrolyze phosphoatidylcholine in the diet

A

pancreatic secretions
intestinal mucosal cells

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11
Q

what enzyme hydrolyzes phosphatidylcholine

A

phospholipases (A1, A2, and B)

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12
Q

after hydrolyzing phsophatidylcholine, the free choline formed enters __

A

after hydrolyzing phsophatidylcholine, the free choline formed enters portal circulation of the liver

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13
Q

how is choline transported to the placenta?

A

in large amounts, choline is pumped against a concentration gradient

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14
Q

all tissues accumulate choline by __ and __

A

all tissues accumulate choline by diffusion and mediated transport

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15
Q

choline uptake is especially important in (5 tissues)

A
  1. liver
  2. kidney
  3. mammary gland
  4. placenta
  5. brain
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16
Q

only a small fraction of dietary choline is __ by __

A

only a small fraction of dietary choline is acetylated by choline acetyltransferase

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17
Q

availability of __ and __ influence choline acetyltransferase activity

A

availability of choline and CoA influence choline acetyltransferase activity

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18
Q

in the brain, what determines the rate of acetylcholine synthesis and why

A

choline availiability bc it is unlikely for choline acetyltranferase to be saturated

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19
Q

choline taken up by the brain may firest enter a __ before it is converted to __

A

choline taken up by the brain may firest enter a storage pool before it is converted to acetylcholine

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20
Q

methyl groups of choline can be used for (2)

A
  1. one-carbon metabolism
  2. conversion to betaine
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21
Q

main sites of choline oxidation

A

liver and kidney

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22
Q

purpose of choline oxidation

A
  1. decrease choline availability to tissues
  2. scavenges methyl groups
  3. ATP generation
23
Q

in utero, fetus is exposed to __ concentrations of choline

A

in utero, fetus is exposed to high concentrations of choline

24
Q

__ is one of the few non-nervous tissues to store large amounts of choline as __

A

placenta is one of the few non-nervous tissues to store large amounts of choline as acetylcholine

25
Q

choline acetyltransferase acetyaltes a __ fraction of dietary choline

A

choline acetyltransferase acetyaltes a small fraction of dietary choline

26
Q

choline acetyltransferase is concentrated in __ and __

A

choline acetyltransferase is concentrated in cholinergic neurons and placenta

27
Q

choline acetyltransferase depends on availabilityof (2)

A
  1. choline
  2. CoA
28
Q

large precursor pool of choline used for acetylcholine synthesis is found in __ in cholinergic neurons

A

large precursor pool of choline used for acetylcholine synthesis is found in choline phospholipids in cholinergic neurons

29
Q

main sites of choline oxidation

A

liver and kidney

30
Q

choline oxidation forms __

A

choline oxidation forms betaine

31
Q

oxidation of choline steps

A
  1. Choline is oxidized to Betaine aldehyde in the inner mitochondrial membrane
  2. Betaine aldehyde dehydrogenase oxidizes betaine aldehyde to form betaine.
  3. Betaine cannot be reduced back to choline; oxidation pathway diminishes availability of
    choline
32
Q

mice without choline dehydrogenase couldn’t produce

A

ATP

33
Q

making phosphatidylcholine: enzyme 1

A

choline kinase

34
Q

making phosphatidylcholine: enzyme 2

A

CTP PC

35
Q

rate limiting step in phosphatidylcholine biosynthesis

A

CTP PC

36
Q

deficiency of CTP PC in lungs of premature infants causes

A

respiratory distress syndrome

37
Q

cholesterol __ CTP PC

A

cholesterol inhibits transcription of CTP PC

38
Q

cholesterol stimulates __, which __ transcription of CTP PC gene

A

cholesterol stimulates SRE, which inhibits transcription of CTP PC gene

39
Q

alternative pathways of phosphatidylcholine production can occur in (3)

A

liver
brain
mammary glands

40
Q

choline defieicny compromises __ and __ function

A

choline defieicny compromises liver and kidney function

41
Q

choline is necessary for __ transport

A

choline is necessary for carnitine transport

42
Q

when is demand for choline extra high?

A

pregnancy and lactation

43
Q

premenopausal women have __ capacity for synthesis of choline
choline prevents __ dysfunction in them

estrogen

A

premenopausal women have enhanced capacity for synthesis of choline
choline prevents developing organ dysfunction in them

44
Q

ppl with enough folate and B12, but not enough choline had

A

liver damage and muscle damage

45
Q

choline and brain development

A

essential!
brain extracts choline best during neonatal period (first 4 weeks of life)

46
Q

epigenetics: choline deficiency decreases __ concentrations, resulting in DNA __

A

epigenetics: choline deficiency decreases SAM concentrations, resulting in DNA hypomethylation

47
Q

DNA methylation is necessary during __ development for __

A

DNA methylation is necessary during fetal development for neurogenesis

48
Q

in adults, choline accelerates the synthesis and release of __ in nerve cells

A

in adults, choline accelerates the synthesis and release of acetylcholine in nerve cells

49
Q

phosphatidylcholine is carried into neurons as part of

A

apolipoprotein E

50
Q

reduced phosphatidylcholine and choline is associated with __

A

reduced phosphatidylcholine and choline is associated with Alzheimer’s disease

51
Q

in mice, choline-rich diet diminished __ loss

A

in mice, choline-rich diet diminished memory loss

52
Q

in rodents, choline (and methyl) deficiency led to __ in the liver which leads to liver __

A

in rodents, choline (and methyl) deficiency led to lipid accumulation in the liver which leads to liver fibrosis

53
Q

choline deficiency sensitizes hepatocytes to __ and __ carcinogens

A

choline deficiency sensitizes hepatocytes to liver and breast carcinogens

IHN: Biochemistry 2 (38 decks)

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