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Nutr 3330 > Midterm 1 (Lec 2 > Flashcards

Midterm 1 (Lec 2 Flashcards

1
Q

Thiamin structure

A

REFER TO DIAGRAM ON SLIDE 2
Pyrimidine, methylene bridge, thiosol ring

Phosphates are added in order to synthesize the coenzyme thiamin pyrophosphate (TPP)

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2
Q

Thiamin (B1) Metabolic role

A

Facilitates energy release from foods (like all other micronutrients)
Central role in carbohydrate metabolism
Coenzyme form is thiamin pyrophosphate

Thiamin pyrophosphate is needed by three enzymes:
Pyruvate dehydrogenase, alpha KG dehydrogenase ( oxidative decarboxylations) and transketolase

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3
Q

TPP needed for pyruvate dehydrogenase

A

Pyruvate dehydrogenase is central in carb metabolism (oxidative decarboxylation)

It enables Pyruvate to acetyl CoA which lets acetyl coA finally enter the TCA cycle

MAGNESIUM ALSO NEEDED
|NIACIN AND PANTOTHENIC ACID ALSO INVOLVED (LECTURE 3)|

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4
Q

Acetyl CoA

A

Central in macronutrient metabolism (carbs protein and fat all oxidized to acetyl CoA
Another fate is entrance into citric acid cycle (final common pathway for oxidation of macronutrients)

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5
Q

TPP NEEDED FOR ALPHA KETOGLUTARATE DEHYDROGENASE

A

Alpha kg dehydrogenase is part of the TCA cycle (oxidative decarboxylation)
Since TPP is needed for the function of alpha kg dehydrogenase, and alpha kg dehydrogenase is part of the TCA cycle, we can say thiamin is needed to facilitate the metabolism of carbohydrates

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6
Q

TPP needed for Transketolase

A

Transketolase is in the penthouse phosphate pathway ( carb metabolism and alternative route for glucose metabolism)

NADPH is generated which is then used for fatty acid synthesis and steroid synthesis

Ribose also generated for nuclei acid synthesis

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7
Q

Thiamin (B1) Deficiency

A

Discovered in chicks
BERI BERI
- anorexia with weight loss
- neurological symptoms
- paralysis
- cardiovascular and respiratory

Rapidly reversed with thiamin but rare due to enrichment of Canadian flour - an example of regulatory activity

More common degrees of deficiency found in diabetics and hyper metabolism and hindered carb metabolism

THREE TYPES

WET (Edema)
-cardiovascular, respiratory
- heart swelling
- pulmonary congestion

DRY (no edema)
- central nervous system impairment
- alcoholics (wernicke korsakoff syndrome)
- memory loss, confusion, confabulation (honest lying)

INFANTILE
- breast fed infants of deficient mothers
- vomiting, diarrhea, convulsions
- aphonia (silent crying)
- sudden death can occur
- responds to thiamin quickly

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8
Q

Thiamin deficiency and diabetes

A

Related to need for thiamin as a coenzyme in carb metabolism

Thiamin replacement in diabetes is linked to improvements in glucose metabolism, inflammatory status and vascular function

Transketolase (a thiamin dependent enzyme) can be used to assess thiamin status) but it also NEEDS MAGNESIUM

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9
Q

Thiamin Health Claims in Europe

A

Thiamin contributes to normal carbohydrate and energy yielding metabolism (infants to 18)

Thiamin contributes to maintenance of normal neurological function ( infants to 3) -related to dry BERI BERI?

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10
Q

Riboflavin (B2)

A

Water soluble, yellow, fluorescent
Essential for conversion of vitamin b6 to its coenzyme forms

COENZYME FORMS
- FAD
-FMN

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11
Q

FMN AND FAD metabolic roles

A

Accept and donate hydrogen atoms (redox reactions)

Part of flavin dependent enzymes (flavoproteins) eg; amino acid oxidases

Needed in many places of the TCA cycle and energy production - crucial in conversion of food energy to ATP

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12
Q

Riboflavin is involved in H transfer

A

REFER TO PDF

PDF shows:
- components of riboflavin structure
- Illustrates hydrogen transfer
- action is at the nitrogen

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13
Q

Riboflavin (b2) food sources

A

Milk products
Photolabile
Eggs
Meat
Fortified flour in Canada

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14
Q

Riboflavin (b2) deficiency

A

No specific term

  • lesions and dermatitis of lips and mucosa of mouth
  • cheilosis and angular stomatitis (cracks at mouth)
  • Magenta tongue
  • Sore throat

RIBOFLAVIN DEFICINCY AFFECTS VITAMIN B6
- if there’s no riboflavin then B6 will accumulate in the body and can’t be broken down
- study shows riboflavin is a limiting nutrient for maintaining adequate vitamin b6

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15
Q

Riboflavin and iron

A

Riboflavin deficiency can interfere with iron status

Riboflavin deficiency can
- impair mobilization of iron from its storage protein
- impair iron absorption
- increase intestinal loss of iron
- impair iron utilization for synthesis of hemoglobin

Riboflavin supplements may help anemia (improves hemoglobin status)

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16
Q

Riboflavin and migraines

A

Riboflavin supplements shown to help migraines by:
- keeping glutathione in its reduced state
- anti inflammatory effect

Active dose is 400 mg riboflavin/day (way higher than what we need)

17
Q

Niacin (B3) Structure

A

Two chemical structures
- nicotinic acid (drug form)
- nicotinamide (major form in blood)

COENZYME FORMS
- NAD(H)
- NADP(H)
Action at the nitrogen

B3 is unique because it can be synthesized from tryptophan (essential AA)

18
Q

Kynurenine Pathway *** important

A

Kynurenine is a key intermediate of tryptophan becoming niacin

Kynurenine needs riboflavin (B2) and vitamin B6

Replaces need for niacin in animals

Tryptophan (eaten) -> kynurenine-> vitamin b6 -> NAD/NADP (coenzyme forms of niacin)

19
Q

Niacin (b3) Metabolic role

A

Central in macronutrient metabolism
Transfers hydrogen during metabolic reactions
Reduction and oxidation reactions
At least 200 enzymes (niacin involved in a lot of pathways)

20
Q

Niacin (b3) redox reactions

A

Reduction
- acts as hydrogen DONOR
- NADPH Becomes NADP
- reductive biosynthesis of fatty acids and steroids

Oxidation
- acts as hydrogen ACCEPTOR
- NADP becomes NADPH
- oxidation of numerous fuel molecules (Pyruvate TCA intermediates etc)

21
Q

NiacIn (b3) deficiency

A

PELLAGRA (rough skin)

Four D,s
- diarrhea
- dermatitis
- dementia
- death

22
Q

Groups at risk for niacin deficiency regardless of intake

A

Long term treatment for tuberculosis with isoniazid - drug interferes with Kynurenine pathway

Hartnups disease (genetic disorder)
- defect in absorption of tryptophan

Carcinoid syndrome
- tryptophan used for serotonin synthesis which compromises Kynurenine pathway

Nicotinamide treatment helps

23
Q

Niacin- plague of corn

A

Corn was replaced as main protein source in 1900,s
But niacin is bound as niocytin in corn and nutritionally unavailable AND corn is low in tryptophan

Led to pellagra and more deaths than any nutrition related disorder

Alkali treatment breaks bond and makes niacin available (corn is washed with lime water)

24
Q

Niacin and CVD

A

Nicotinic acid is a long time cholesterol lowering drug
Decreases LDL cholesterol, increases HDL cholesterol
Prevents progression of atherosclerotic lesions in coronary arteries
Inexpensive, used with other drugs

25
Q

Niacin flush

A

Common side effect of niacin treatment
- ab pain, rash, liver toxicity
Rapidly absorbed by GI tract

Can be reduced by
- taking niacin with meals
- avoiding hot liquids and alcohol after dose
- working dose up gradually
Extended release niacin released by FDA and reduces side effects

Nutr 3330 (21 decks)

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