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Flashcards in B complex Deck (37):
1

B1

thiamine

2

B2

riboflavin

3

B3

niacin

4

B5

pantothenic acid

5

B6

pyridoxine

6

B12

cobalamin

7

Thiamine/B1 RDA

F - 1.1 mg/day
1.5 mg/day needed in pregnancy and lactation
M - 1.2 mg/day

8

Thiamine/B1 active form

thiamine pyrophosphate (TPP)
= 95% of B1 in animals
[plants = non-phosphorylated form]
requires Mg and ATP for phosphorylation to active form

9

Thiamine/B1 functions

coenzyme
- energy transformation
- synthesis of NADP
- synthesis of RNA and DNA
- nerve conduction (regulates sodium channels)

10

Thiamine/B1 functions: energy transformation

enzymes:
- PDH
- alpha ketoglutarate dehydrogenase
(also require B2, B3, and lipoid acid)
- transketolase (NADPH and pentose synthesis)

11

Thiamine/B1 deficiency

mild = fatigue, insomnia, HAs
beriberi
- dry: peripheral neuropathy, diminished reflexes, muscle spasm/pain/tenderness
- wet: CV manifestions - tachycardia, cardiomegaly, peripheral edema, CHF
- cerebral (W-K syndrome): ophthalmoplegia, ataxia, memory loss/confusion

12

Thiamine/B1 food sources

whole grains
enriched flour
nuts/seeds = esp sunflower
legumes
peas

13

Coenzymes made with riboflavin/B2

FAD - flavin adenine dinucleotide
FMN - flavin mononucleotide

14

Riboflavin/B2 RDA

F - 1.1 mg/day
M - 1.3 mg/day

15

Riboflavin/B2 absorption

bound to protein, must be released by HCl and peptidases
95% absorbed in proximal SI up to 25 mg
stored for 2-6 weeks

16

Riboflavin/B2 functions

FMN and FAD = part of flavoproteins
- metabolism of carbs, lipids, proteins
- redox rxns: ETC, CYP450 metabolism, beta-oxidation
Dopamine synthesis (monoamine oxidase)
Uric acid metabolism (xanthine oxidase)
Glutathione regeneration (glutathione reductase)
Vitamin metabolism (B6, B3, folate)

17

Riboflavin/B2 excess

none known

18

Riboflavin/B2 deficiency

= rare, called ariboflavinosis
cheilosis
angular stomatitis
glossitis
seborrheic dermatitis

may lead to high homocysteine levels

19

Increased risk for riboflavin/B2 deficiency

DM
stress
OCP
alcoholism

20

Riboflavin/B2 food sources

dairy (highest)
eggs
mushrooms
meat
almonds
leafy greens
grains

21

Niacin/B3 RDA

F - 14 mg/day
M - 16 mg/day
can be synthesized endogenously from tryptophan (2-3%)
[aka nicotinic acid/niacinamide]

22

Niacin/B3 bioavailability

stable in foods (minimal loss from cooking/storing)
bound in complex carbs - corn/wheat
- only 10% available for absorption

23

Niacin/B3 functions

Redox rxns
- pyruvate decarboxylase
- oxidation of acetylCoA in TCA cycle
- beta-oxidation
- oxidation of alcohol
- biosynthesis of FAs and cholesterol
- proline synthesis
- glutathione and vit C regeneration
- folate synthesis
NADP used for anabolism/NAD used for catabolism

24

Niacin/B3 excess

= from supplementation
hepatotoxicity and incr liver enzymes
niacin flush d/t histamine release, PGE2 and PGD2
GI distress - N/V

25

Niacin/B3 deficiency

= pellagra
dermatitis - symmetrical, thick, scaly
diarrhea - N/V, glossitis, angular stomatitis
dementia - HA, apathy, disorientation
death

26

Niacin/B3 food sources

meat
fish
peas
peanuts
mushrooms
eggs
enriched grains

27

Pantothenic Acid/B5 adequate intake

5 mg/day
US consumption = 4-7 mg/day

28

Pantothenic acid/B5 absorption

85% = bound to CoA in food
absorbed as pantothenic acid in jejunum via sodium-dependent multivitamin transporter

29

Pantothenic acid/B5 absorption

component of CoA
= necessary for synthesis of lipids, cholesterol, steroid hormones, ACh, melatonin
- component of intermediaries in TCA cycle and beta-oxidation
Acetylation rxns:
- changes in protein structure
- cell signaling
- DNA replication
- gene expression

30

Pantothenic acid/B5 deficiency

very rare
burning feet syndrome

31

Pantothenic acid/B5 food sources

meat
egg yolk
mushrooms
potatoes
avocado
cruciferous vegetables
yogurt
whole grains

32

Pyridoxine/B6 absorption

active form = pyridoxal 5-phosphate (PLP)
75% absorbed
destroyed by milling, refining, cooking

33

Pyridoxine/B6 RDA

F - 1.5 mg/day
M - 1.7 mg/day

34

Pyridoxine/B6 metabolism

liver = primary site; stores 5-10%
muscle stores 75-80%
half-life = 3-4 weeks

35

Pyridoxine/B6 functions

Protein metabolism
- AA biosynthesis: trans/deamination
- Neurotransmitter synthesis: Serotonin, DA, GABA
- Hemoglobin synthesis
- Glucose metabolism: gluconeogenesis and glycogenolysis
- nucleic acid synthesis: homocysteine metabolism

36

Pyridoxine/B6 deficiency

hyperhomocysteinemia
depression/depressed mood
sideroblastic anemia, usu normocytic or macrocytic

37

Pyridoxine/B6 food sources

fish - salmon, tuna
meat
sunflower seeds
spinach
grains
potatoes
bananas
nuts