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NUTR3210 > Micronutrients (Enzyme Cofactors) > Flashcards

Micronutrients (Enzyme Cofactors) Flashcards

1
Q

What are the sources of biotin?

A
  • made by intestinal bacteria (not enough tho)
  • found in foods bound to proteins
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2
Q

How does biotin circulate in the blood?

A

freely, some bound to albumin

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3
Q

Why is there no RDA or deficiency for Biotin?

A

It’s very prevalent

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4
Q

What B vitamin is Biotin?

A

B7

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5
Q

What are the 3 key reaction involving biotin?

A
  1. pyruvate carboxylation
  2. malonyl CoA
  3. Propionate -> glucose conversion (ruminants)
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6
Q

What does the carboxyl group of biotin react with in an enzyme?

A

NH2 group of a lysine side chain
(carboxyl group then gets transferred)

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7
Q

What B vitamin is Folate?

A

B9

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8
Q

Where is folate found?

A
  • folate - in food
  • folic acid - in supplements and fortified foods (synthetic)
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9
Q

What are the three parts of folate?

A

Pterin ring, PABA, glutamic acid

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10
Q

What is the importance of folate?

A
  • nucleic acid precursor formation
  • amino acid formation
  • methylation reactions
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11
Q

Natural folates have multiple ____ residues that must be removed for absorption (folic acid is already in this form, so no digestion required)

A

glutamate

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12
Q

Most natural folates and folic acid are converted into bioactive ____ in the intestine

A

5-methyltetrahydrofolate (5-methyl THF)

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13
Q

How is folate absorbed?

A

proton-coupled folate transporter (PCFT)

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14
Q

How is folate transported in the blood?

A

bound to proteins like albumin

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15
Q

What is the active form of folate?

A

5-methyl THF

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16
Q

What is the difference between folic acid and folate?

A
  • folate = 1 glutamate residue
  • folic acid = multiple glutamate residue
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17
Q

What B vitamin is Cobalamin?

A

B12

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18
Q

Cobalamin is a generic term for ____

A

corrinoids ; named for corrin nucleus with cobalt

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19
Q

Where is cobalamin found?

A
  • made by bacteria ONLY
  • animal products
  • NO plant provitamin
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20
Q

What other micronutrient does a cobalamin deficiency affect?

A

folate

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21
Q

How is cobalamin absorbed?

A
  • in the stomach
  • binds to intrinsic factor secreted from stomach lining
  • B12-IF complex goes to small intestine receptor
  • complex broken down, B12 absorbed, IF released back into intestinal lumen
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22
Q

What are the “key players” in single carbon metabolism?

A
  • folate (N5-methyl THF or N5,N10-methylene THF)
  • Vit. B12
  • S-adenosyl methionine (SAM)
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23
Q

In simple terms, what happens in single carbon metabolism?

A

methyl transfers, to eventually form dTTP that is involved in DNA synthesis and cell division, and the SAM cycle - also involved in DNA processing

24
Q

The folate trap is an absence of ____ that causes ____

A
  • vit. B12
  • inhibition of the SAM cycle (arrest at N-5-methyl THF production from free folate
25
Q

What is the main form of vitamin B6 in blood

A

pyridoxal phosphate (PLP)

26
Q

Vit. B6 exists as ____ vitamers called:

A
  • 6
  • pyridoxine (plant provitamin)
  • pyridoxal
  • pyridoxamine
    all can be phosphorylated or dephosphorylated
27
Q

Vit. B6 is ____ before absorption

A

dephosphorylated

28
Q

high levels of vit. B6 are found in ____

A

muscle

29
Q

What B vitamin is niacin?

A

B3

30
Q

In what form is niacin found in plants?

A

nicotinic acid (provitamin)

31
Q

In what form is niacin found in animal-derived food

A
  • nicotinamide
  • nicotinamide adenine dinucleotide (NAD)
  • nicotinamide adenine dinucleotide phosphate (NADP)
32
Q

nicotinic acid and nicotinamide are precursors for ____ in the body

A
  • NAD
  • NADP
33
Q

How does niacin circulate in the plasma

A

free nicotinamide

34
Q

NAD+ reduced to NADH has a role in _____

A

catabolism

35
Q

What has to happen to nicotinic acid before it can be converted to NAD(P)?

A
  1. converted to amide
  2. build into dinucleotide structure
36
Q

Where is riboflavin found?

A

animal-derived

37
Q

How is riboflavin absorbed?

A
  • must be released from bound proteins (by HCl in stomach)
  • absorbed from gut lumen by active transport: riboflavin transporter 2 (RFT2)
38
Q

How are riboflavin, FAD and FMN transported in the body?

A

bound to proteins like albumin

39
Q

production of riboflavin is positively regulated by the hormone:

A

T3 which increases flavokinase enzymatic activity

40
Q

Order FMN, FAD and riboflavin in order of their conversion from the diet

A

riboflavin -> FMN -> FAD

41
Q

What is riboflavin’s role in glutathione reductase?

A

FAD accepts electrons from NADPH and gets reduced to FADH2, then FADH2 gives its electrons to GSSG to regenerate GSH

42
Q

How does thiamine exist in plants?

A

thiamine provitamin

43
Q

how is thiamine found in animals?

A

in its phosphorylated form; thiamine pyrophosphate (TPP) - ACTIVE FORM

44
Q

How is thiamine (TPP) found in plasma?

A

in free form or bound to albumin

45
Q

What enzyme converts the plant provitamin version of thiamine to TPP and how?

A

thiamine diphosphokinase ; adds two phosphate groups

46
Q

What are the two parts of TPP, which is the active site?

A
  • carbanion -> active
  • 2 phosphate groups
47
Q

Which oxidative decarboxylation steps is TPP important in?

A
  1. pyruvate dehydrogenase complex
  2. a-ketoglutarate dehydrogenase
48
Q

Where is pantothenic acid found?

A

EVERYWHEREEEE

49
Q

What B vitamin is pantothenic acid?

A

B5

50
Q

How is pantothenic acid found in the blood?

A

freely

51
Q

How is pantothenic acid absorbed?

A

sodium-dependent multivitamin transporter (SMVT)

51
Q

what is pantothenic acid a precursor for?

A

CoA

52
Q

What are the functions of pantothenic acid?

A

energy metabolism ; allowing Kreb’s cycle to take place

52
Q

What is the active form of pantothenic acid in fatty acid synthesis?

A

4-phosphopantetheine

53
Q

What is the active form of pantothenic acid in oxidative reactions?

A

CoA

54
Q

What is Beriberi caused by?

A

Thiamine deficiency

55
Q

What is pellagra caused by?

A

Niacin deficiency

NUTR3210 (13 decks)

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