2. Thiamin, riboflavin, niacin Flashcards Preview

Nutrition 3330 > 2. Thiamin, riboflavin, niacin > Flashcards

Flashcards in 2. Thiamin, riboflavin, niacin Deck (92):
1

General functions of B vitamins (4)

1. micronutrient metabolism
2. energy production ATP
3. energy release
4. carbon metabolism - transfer of single carbon units

2

Coenzymes

required for the activity of enzymes

3

enzymes

at as catalysts, drive many reactions and pathways

4

relation of B vitamins and coenzymes?

part of the "structure" of coenzymes

5

T/F
B vits work together?

True

6

Vitamins are involved in Intermediary Metabolism of ...? (5)

1. Carbs
2. Proteins
3. Fats
4. ATP Generation
5. Nucleic Acids/Fatty Acids/Steriods

7

Carb metabolism pathways vitamins are involved in?

glycolysis and gluconeogenesis

8

Protein metabolism pathways vitamins are involved in?

Protein synthesis and amino acid oxidation

9

Fat metabolism pathways vitamins are involved in?

FA synthesis and Beta oxidation

10

ATP generation metabolism pathways vitamins are involved in?

Respiratory chain and oxidative phosphorylation

11

Nucleic Acids/Fatty Acids/Steriods metabolism pathways vitamins are involved in?

pentose phosphate pathways

12

What is added to thiamine to synthesize its coenzyme form?

Phosphates

13

What is thiamines coenzyme form?

Thiamine pyrophosphate (TPP)

14

Thiamine's main metabolic role

- facilitates energy release from foods
- central role in carb metabolism

15

Reactions thiamine is involved in?

2 types
multiple enzymes

1. Oxidative decarboxylations:
- pyruvate dehydrogenase
- alpha-ketoglutarate dehydrogenase

2. Transketolase Reactions:
- transketolase (requires magnesium)

16

Thiamines short form?

B1

17

thiamine requires what other vitamin to perform transketolase reactions?

Magnesium

18

TCA cycle full name?

Citric Acid Cycle

19

Thiamine deficiency?

Beri-Beri

20

Translation of beri-beri?

i can't i cant

21

Symptoms of beri beri?

*** anorexia + weight loss
neurological symptoms
paralysis
cardiovasc + resp

22

What deficiency causes beri-beri?

thiamine

23

T/F
-disease can't be reversed

False:
Thiamine reverses disease rapidly

24

Why is beri beri rare?

Thiamine is fortified in Canadian flour since 1949

25

What is thiamine fortified in?

Canadian Flour

26

3 types of beri-beri?

1. Wet (edema)
2. Dry (no edema)
3. Infantile

27

Symptoms Wet beri-beri (edema)

cardio-resp
- heart swelling
- pulmonary congestion

28

Symptoms dry beri-beri (no edema)

-central nervous system impairment
-(alcohol - Wernicke-Korsakoff Syndrome)
-confusion, memory loss, confabulation

29

What does edema mean?

Swelling

30

What does "confabulation" mean?

memory disturbance

-fabricated, distorted or misinterpreted memories about oneself or the world, without the conscious intention to deceive

31

Cause of Infantile beri-beri?
Symptoms?

breast fed infants of deficient mothers

- vomiting, diarrhea, convulsions
- aphonia
- sudden death can occur

32

what is "aphonia" ?

inability to produce voice

33

Thiamine deficiency has been identified in what major disease? (Why?)

Diabetes

(Consider role of thiamine in glucose metabolism)

34

3 benefits of thiamine? (particularly in diabetes patients)

improved glucose metabolism, imflammatory status and vascular function

35

2 Health claims in Europe regarding thiamine?

- Normal carb and energy-yeilding metabolism
- Maintenance of normal neurological function

36

Why is riboflavin called B2

2nd B vit discovered

37

3 forms of riboflavin?

1. Riboflavin
2. Flavin Mononucleotide FMN (added Phosphate)
3. Flavin Adenine Dinucleotide FAD (added phosphate, ribose and adenine)

*FMN and FAD are the coenzyme forms

38

Riboflavin essential for what conversion?

conversion of B6 to is co-enzyme forms

39

Riboflavins coenzyme forms?

FMN - Flavin Mononucleotide
FAD - Flavin Adenine Dinucleotide

40

Riboflavin's metabolic roles?

accept/donate hydrogen (on OH 3)
- FAD

Flavin-dependent enzymes (flavoproteins)
- Electron Transport Chain (Respiratory Chain)

41

Riboflavin involvement in TCA cycle?
Relation to the electron transport chain?

TCA Cycle
- FAD accept 2H+ from Succinate --> Fumarate

Electron transport chain
- FADH2 involved with coenzyme Q

42

Riboflavin involvement in TCA cycle?
Relation to the electron transport chain?

TCA Cycle (OH 1 and 4)
- FAD accept 2H+ from Succinate --> Fumarate

Electron transport chain
- FADH2 involved with coenzyme Q

43

Photolabile

susceptible to change with light

44

Riboflavin food sources?
Fortified in?

Milk products, liver, meat

fortified flour in Canada

45

What processing destroys thiamine and riboflavin?

Milling of wheat

46

True/False
Riboflavin deficiency can be fatal?

False
Deficiency is non specific and never fatal

47

Symptoms of riboflavin deficiency

lesion symptoms
- cheilosis
- megenta tongue
- angular stomatitis (mouth)
- soborrheic dermatitis (skin)

48

**What other vitamin could riboflavin def affect?

Iron

Why??

49

Iron status can be interfered with from what vitamin deficiency

riboflavin

50

How does riboflavin deficiency affect iron? (2)

1. Impairs mobilization of iron from its storage protein (ferritin)
2. Impairs iron absorption

51

Studies of women show correcting a marginal riboflavin deficiency improves _____ status

(other than but related to iron)

hemoglobin status

52

B3 name

Niacin

53

Niacins other name

B3

54

2 chemical structures of niacin?
(where are they found)

Nicotinic Acid (drug form)
Nicotinimide (major blood circulating form)

55

2 Co-enzyme forms of niacin?

NAD(H) - Nicotinamide adenine dinucleotide
NADP(H)

56

Where does the action occur for the coenzymes of Niacin?

at the Nitrogen

57

Niacin can be synthesized from what amino acid?

tryptphan

58

What ratio is niacin synthesized from tryptophan?

60mg tryptophan = 1mg of niacin

59

What macronutrient must be considered when calculating niacin intake?

Protein
- niacin can be synthesized from the amino acid tryptophan

60

meaning of Niacin Equivalent?

units used to express niacin content of food. It represents preformed niacin plus tryptophan equivalents (60 mg tryptophan = 1 mg niacin).

61

Kynurinine Pathway

a metabolic pathway leading to the production of nicotinamide adenine dinucleotide (NAD+) from the degradation of the essential amino acid tryptophan

62

What is the key intermediate in kynurenine pathway

kynurenine

63

What vit(s) are needed in the Kynurinine Pathway?

riboflavin + B6

64

Does Kynurinine Pathway produce enough niacin?

No, niacin still essential in the diet

* completely replaces need in rodents dogs and pigs

65

Major steps and vitamins involved in the Kynurinine Pathway

Tryptophan --> Kynurine --> NAD/NADP

(riboflavin and B6 needed for Kynurine --> NAD/NADP)

66

Metabolic role of niacin (3)

- macronutrient metabolism
- transfers hydrogen during metabolic reactions
- oxidation/reduction reactions

67

How many enzyme is niacin involved with?

Atleast 200

68

Where is niacin used in the TCA cycle?

all NAD+ --> NADH+H+

1. ** Pyruvate --> Acetyl CoA

2/3. Isocitric Acid --> alpha ketoglutaric acid --> succinyl-Coa

4. Malic Acid --> Oxaloacetic Acid
(final step, re-enters TCA cycle)

69

Niacin in the Electron Transport Chain?

10 NADH enter the start from 1 molecule of glucose

Decarboxylation reactions:
2 NADH glucose--> pyretic acid (Glycolysis)
2 NADH pyruvate --> acetyl CoA
6 NADH (TCA cycle)

70

Niacin in Glycolysis/Gluconeogenesis

Glycolysis:
Glyceraldehyde-3-phosphate --> 1,3 Biphosphoglycerate

NAD+ --> NADH+H+

Gluconeogenesis:
reverse

71

Niacin in Pentose Phosphate Pathway

Glucose-6-phosphate --> Ribose-5-phosphate

2x NADP --> NADPH + H+

72

2 purposes of the pentose phosphate pathway?

1. generate "NADPH" used for synthesis of "FA and steroids"
2. generate "ribose" for synthesis of "nucleic acids"

73

Oxidation means hydrogen ______ ?

Acceptor
ex. NAD(P) --> NAD(P)H

74

Reduction means hydrogen ______?

Donor
ex. NAD(P)H --> NAD(P)

75

Niacin "oxidation" is used for the metabolism of? (4)

NAD(P) --> NAD(P)H

Pyruvate, TCA intermediates, glycolysis intermediates, pentose phosphate pathway

76

Niacin "reduction" is used for?

NAD(P)H --> NAD(P)

Reductive biosynthesis of fatty acids and steroids

77

Where is NADPH generated?

Pentose Phosphate Pathway

78

Pellagra is italian for?

rough skin

79

What disease is associated with Niacin deficiency

pellagra

80

Pellagra is associated with a deficiency of what vitamin

Niacin (B3)

81

Symptoms of pellagra

4 D's
-diarrhea
-dermatitis
-dementia
-death

*case study OH 7

82

Hartnup's Disease

Improved with?

- Autosomal recessive disorder
- Develop pellagra (niacin deficiency) due to defect in absorption process for Tryptophan

improved with nicotinamide treatment

83

Causes of pellagra symptoms in absence of dietary niacin deficiency? (2)

- Isoniaizid; prolonged treatment (drug competes with B6, needed in the Kururenine pathway)

- Hartnup's Disease (autosomal recessive disorder, defect in tryptophan absorption)

84

Problem with niacin in corn?
How to fix it?

Niacin bond and unavailable
- also low in tryptophan

Alkali treatment (ex. lime water) breaks bond

85

Niacin requirement is expressed as?

Niacin Equivalent (NE)

86

Niacin (Nicotinic Acid) typically used to treat what disease? Why?

CVD
Cholesterol lowering agent

87

Why is Nicotinic Acid unique among lipid-lowering drugs (such as statins)

Reduce LDL cholesterol (typical)

Increase HDL cholesterol
Decrease Lipoprotein (a)

88

Benefits of niacin (nicotinic acid) with cardiovascular disease?

-lowers LDL and lipoprotein (a)
-increase HDL
-prevents progression of atherosclerotic lesions in coronary arteries

often used in combination with other drugs

89

Did increase HDL studies (from niacin) show decrease in heart attacks, strokes or need for angioplasty?

no
LDL lowering showed greater heart stability but no correlation to HDL levels

90

Niacin Flush

common side effect to niacin treatment
- abdominal pain, rash, liver toxicity
- rapidly absorbed GI tract

91

How to reduce niacin flush symptoms?

take with meals
avoid hot liquids + alcohol
work dose up gradually
-- Extended-release niacin (Niaspan)

92

Large scale niacin flush problem?

Uncle Ben's Rice
- excessive Niacin when served in food service establishments