Vitamin B Flashcards by Angela Luo

what are the 3 major functions of thiamin?

energy transformation (remove CO2), synth of pentoses and NADPH (PPP), membrane and nerve conduction

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what is the noncoenzyme form of thiamine associated possibly with beriberi?

TTP

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what is the coenzyme form of thiamine?

TPP

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what are food sources of thiamine?

whole grains, seeds and legumes, pork, enriched white flour and minute rice, veg and fruit

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2 situations where beriberi occurs?

1) lack of thiamin in diet

2) alcoholism (secondary)–>Wernicke encephalopathy

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examples of foods with thaminase?

raw fish, raw ferns/Nardoo

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examples of foods with anti-thiamin factors?

fermented tea and betel nut (polyhydroxyphenols)

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what are symptoms of Wernicke enephalopathy?

ocular motor signs, ataxia, derangement of mental functions

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what is the static test of thiamin? What is the functional test?

urinary excretion (recent intake); RBC transketolase activity (measures usage thru stimulation test)

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what is the enzyme stimulation test?

erythrocyte transketolase activity test: in vitro stimulation–>if stimulated activity >20%=marginal deficiency, if >25% = deficient

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what is the EAR and what is based on?

1.0 mg for men, 0.9 for women; depletion/repletion ETKA

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what is the RDA?

1.2 in men and 1.1 in women

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What is the name of vitamin B2?

riboflavin

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what coenzymes are riboflavin involved in?

FMN, FAD

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what are the three components of a nucleotide?

base, sugar, phosphate

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FMN+AMP=?

FAD

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what are the two functions of riboflavin?

1) add or remove hydrogens

2) metabolism of other vitamins

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glutathione reductase is found in____

red blood cells

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if low in riboflavin, will have 2ndary deficiency in:

B6, folate, vit A, niacin, choline

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what reactions need FAD?

succinate–>fumarate; pyruvate–>Acetyl CoA

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what reactions need FADH2?

GSSG–>2GSH; breakdown fatty acids

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what are food sources of riboflavin?

milk, whole grains, enriched grains, meat

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What is deficiency in riboflavin called?

ariboflavinosis

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what is the key symptom of ariboflavinosis?

cheilosis

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what is the static test? what is the functional test? (For riboflavin)

urinary riboflavin; EGR stimulation test

what is EGRAC?

Erythrocyte glutathione reductase activity coefficient-->determined thru stim test: % above unstimulated enzyme activity

what is the EAR for riboflavin? what is the RDA?

1.1mg M/0.9mg F; 1.3mg M/1.1mg F (2 SDs away from EAR)

what is vitamin B3?

niacin

an AC for riboflavin > ___ shows deficiency

1.4

what are the two chem forms of niacin?

nicotinic acid and nicotinamide

what are some noncoenzyme roles for niacin?

donates ADP ribose to chromosomal proteins, histones (gene silencing)

what are 5 coenzyme roles of niacin?

1) pyruvate dehydrogenase 2) synth of f.a.(donate H) 3) krebs cycle (3 rxns) 4) regenerate antioxidants 5) activate other vitamins

what are the 3 rxns in Krebs that use niacin as coenzyme?

malate-->oxaloacetate; isocitrate-->alphaketoglutarate; alphaketoglutarate-->succinyl coA

Niacin is an inhibitor of ____ , preventing gene silencing

sirtuin (Sir-2)

what are the 2 ways to obtain niacin?

exogenous (food), endogenous (made from tryptophan)

what is the bound form of niacin?

niacytin

1 NE= __ mg niacin = ___ mg tryptophan

1; 60

if you are deficient in ____ can't convert TRP into niacin

Vit B6 (PLP)

assume good quality protein have ___% TRP

how to calculate NE from protein intake?

g protein/100 = g TRP x 1000 = mg TRP / 60 = NE

What are the 3Ms?

maize, molasses (CHO), meat (pork fat)

what are the 3Ds?

diarrhea, dementia, dermatitis

what is niacin deficiency called?

pellagra

why is corn low in quality protein?

only 0.6% TRP, most niacin in bound niacytin form

how can niacin be unbound in corn?

by using lime water (Ca(OH)2)

RDA for niacin for M is __, F is ___

16; 14

what is the most sensitive measure of niacin status?

urinary excretion of niacin metabolites (if low, means deficient)

to set RDA from EAR, niacin uses __% SD

what is niacin's UL?

35 mg from synthetic or fortified sources only (not food or TRP)

what are symptoms of toxicity?

flushing (release of histamine), severe itching, headaches, liver damage

why is synthetic niacin taken?

to lower LDL and increase HDL (affordable-->self-medicate)

what is dermatitis?

"flaky paint" sun exposed skin that rarely happens on face

LOAEL of niacin is set at ___ mg based on ___ reactions. It is lowered to UL based on UF of ___

50; flushing; 1.5

Coenzyme A and acyl carrier protein in fatty acid synthesis has ____

pantothenic acid

when biotin is bound to ___ it is called ___; this is the form found in enzymes

lysine; biocytin

You need ____ to digest (absorb) biotin and also for recycling (removing biotin from lysine in body)

biotinidase

what is a non-Coenzyme role of biotin?

gene expression

3C fatty acid

propionyl

how does propionyl enter TCA cycle?

Propionoyl-CoA+CO2-->D-methylmalonyl-CoA

propionyl CoA carboxylase requires ___ as a coenzyme

biotin

what are the 3 vitamins needed in odd chan entry to TCA?

panthothenic, biotin, B12

biotin is needed for the temporary addition of CO2 for the synthesis of ____

fatty acids

biotin is involved with this amino acid enzyme

leucine

what are food sources of biotin?

whole grain, meat+alt, dairy, egg yolk (esp. high cholesterol)

why are we unable to set an EAR for biotin?

because we rely on intestinal synth for about half our needs

what is the AI of biotin?

30 mcg

how was the AI for biotin set?

set by extrapolating up from infant AI based on human milk content of biotin

Deficiency of biotin is caused by:

eating raw egg whites-->have protein called avidin that tightly binds biotin and prevents absorption (destroyed by cooking) -also in-born errors for defective biotinidase

symptoms of biotin deficiency?

affects brain (hallucinate, lethargic), lethal to infants, alopecia and anorexia

Food sources of pantothenic acid?

it is found in all food groups

what are some functions of acetyl CoA?

In PDH complex, acetylation of cules (acetylcholine), drug metabolism, acetylation/deacetylation of histones, ACP in adding 2-C units to make f.a., wound healing

what is the AI of pantothenic acid?

5 mg

what is the AI of pantothenic acid set on?

based on average intake of US population

what are symptoms of deficiency?

burning feet syndrome

deficiency could occur in chronic diseases like:

type 2 diabetes, alcoholics, inflammatory bowel disease

____ is sometimes fortified with pantothenic acid in Canada

breakfast cereals

what are the hematopoietic B-oomplex vitamins?

folate, B12 and 6, pantothenic acid

Vitamin B Flashcards

(77 cards)