FNDH 620 Exam 3 – 2022 (COMPLETE
SOLUTIONS)
When water soluble vitamins are consumed in excess of body needs, generally the excess is:
A. excreted in the feces;
B. stored in liver, bone, and adipose tissue;
C. excre
...
FNDH 620 Exam 3 – 2022 (COMPLETE
SOLUTIONS)
When water soluble vitamins are consumed in excess of body needs, generally the excess is:
A. excreted in the feces;
B. stored in liver, bone, and adipose tissue;
C. excreted in the urine;
D. not absorbed;
E. none of these. - ✔✔excreted in the urine
Vitamin C acts as a coenzyme by maintaining iron in a reduced state in:
A. collagen synthesis
B. methylation of homocysteine
C. release of energy from nutrients
D. heme synthesis - ✔✔collagen synthesis
As little as 10 mgs/day of vitamin C may be enough to prevent scurvy.
A. True
B. False - ✔✔true
A major role for thiamin is:
A. energy transformation;
B. blood coagulation;
C. collage formation;
D. erythrocyte synthesis;
E. none of above. - ✔✔energy transformationWhy may alcoholics cause thiamin deficiency ?
A. alcohol prevents thiamin uptake;
B. alcohol prevents thiamin utilization;
C. alcohol destroys thiamin activity;
D. Both A and B;
E. None of above. - ✔✔Both A and B
alcohol prevents thiamin uptake;
alcohol prevents thiamin utilization
Riboflavin is required for:
A. formation of active folate;
B. conversion of tryptophan to niacin;
C. function of B6;
D. all of A, B & C;
E. none of these - ✔✔all of A B and C
formation of active folate;
conversion of tryptophan to niacin;
function of B6;
Nicotinamide, but not nicotinic acid, is the form required for the synthesis of nicotinamide adenine
dinucleotide.
A. True
B. False - ✔✔false
How are the recommended intakes of niacin expressed (units)?
A. grams
B. niacin equivalents (mgs)C. in micrograms
D. in milliliters - ✔✔niacin equivalents (mgs)
List four water soluble vitamins that are required by pyruvate dehydrogenase complex. - ✔✔B1, B2, B3,
pantothenic acid (B5)
Bioavailability of biotin is near 0% from wheat.
A. True
B. False - ✔✔True (but it is near 100% from corn)
Intake of raw egg white may cause deficiency of
A. pantothenic acid
B. thiamin;
C. riboflavin;
D. biotin;
E. niacin - ✔✔Biotin
Which of the following is one of the main functions of vitamin B6?
A. coagulation
B. depigmentation
C. transamination
D. antioxidation - ✔✔transamination
Methionine cycle requires:
A. B6;
B. B12;
C. folate;
D. Niacin;
E. All of above. - ✔✔all of the aboveB6; B12; folate; Niacin
Which anemia is related to folate deficiency?
A. Pernicious anemia
B. Megaloblastic anemia
C. Hypochromic microcytic anemia
D. Hemodilution anemia - ✔✔megaloblastic anemia
To protect against birth defects, a higher RDA of folic acid has been suggested for pregnant women
A. True
B. False - ✔✔True
Vitamin B12 is only available from ___products.
A. grain
B. fruit
C. animal
D. vegetable - ✔✔animal
Why the RDA of vitamin B12 is so low?
A. In the liver, free cobalamin can be stored for years
B. Little B12 in the body is degraded
C. Whole body turnover is about 0.1% daily
D. All of A, B, & C
E. None of above - ✔✔all of a b and c
In the liver, free cobalamin can be stored for years
Little B12 in the body is degraded
Whole body turnover is about 0.1% dailyHigh dietary folate may cure megaloblastic anemia caused by:
A. folate deficiency;
B. B12 deficiency;
C. less methionine;
D. both A & B;
E. all of A, B & C. - ✔✔Both A & B
folate deficiency;
B12 deficiency;
Formation of retinol from beta-carotene requires the presence of what B vitamin?
A. ascorbic acid
B. folic acid
C. niacin
D. pyridoxal phosphate
E. None of above - ✔✔Niacin
Dietary fat is not very important regarding the digestion and absorption of pre- and provitamin A forms
A. True
B. False - ✔✔False
Within the nucleus, retinoic acid binds to ______
A. retinoic acid nuclear receptors
B. Transcription factors
C. Retinoid X receptors
D. Retinoic acid response elements
E. Both A and C - ✔✔Retinoid X receptorsWhat % of vitamin D3 from diet is absorbed?
A. 20
B. 30
C. 40
D. 50
E. 100 - ✔✔50%
What form of vitamin D is the major circulating form?
A. calcidiol
B. calcitriol
C. cholecalciferol
D. ergocalciferol
E. None of above - ✔✔Calcidiol
The vitamin D receptor is a member of the super family of nuclear receptors that regulates gene
expression.
A. True
B. False - ✔✔True
What is the principal transport vehicle for vitamin E in the blood?
A. the blood plasma
B. lipoproteins
C. cytochrome P450 system
D. alpha tocopherol - ✔✔lipoproteins
Which mechanism has been proposed but not proved as vitamin E's principal function against chronic
disease prevention?
A. Immune functionB. Cell cycle arrest
C. Anti-proliferation
D. DNA repair
E. Anti-oxidation - ✔✔anti-oxidation
For which vitamin is the tolerable upper limit set because of increased tendency for bleeding?
A. Vitamin A
B. Vitamin D
C. Vitamin E
D. Vitamin K - ✔✔vitamin E
What is the chemical name for vitamin K in green plants?
A. menaquinone
B. menadione
C. phylloquinone
D. Beta carotene - ✔✔phylloquinone
As coenzyme, vitamin K is required in the carboxylation of Gla proteins by converting glutamate residues
to gamma-carboxyglutamate residues.
A. True
B. False - ✔✔True
Vitamin K deficiency is most often observed in:
A. old people
B. adolescents
C. children
D. newborns - ✔✔newborns
Which food group contributes the most calcium to our diet?A. meat
B. dairy
C. fruits/vegetables
D. breads/cereals - ✔✔dairy
The primary function of parathyroid hormone (PTH) is:
A. to reduce blood calcium levelsb.
B. to inactivate calcitoninc.
C. to stimulate calcitriol synthesis in the kidney and then enhance bone calcium levels
D. to enhance blood calcium levels by taking calcium from bone - ✔✔to enhance blood calcium levels by
taking calcium from bone
Which two minerals are part of the bone crystal, hydroxyapatite:
A. Sodium, chloride
B. Sulphur, magnesium
C. Calcium, phosphorus
D. Calcium, potassium - ✔✔Calcium, phosphorus
Which of the following amounts comes closest to the level of sodium typically in our daily diets?
A. 0.5 g/day
B. 1-2 g/day
C. 2-3 g/day
D. 3-5 g/day
E. 5-8 g/day - ✔✔2-3 g/day
All of the following are true about potassium except:
A. It increases blood pressure
B. Is found inside cells
C. Helps regulate water balance and osmotic pressureD. Essential for muscle contractility - ✔✔It increases blood pressure
Oral supplements of ferrous iron are available in complexes with sulfate, succinate, citrate, lactate,
tartate, fumarate or gluconate. The absorption of these nonheme iron supplements could be ______
when ingested with vitamin C or other antioxidants.
A. increased
B. decreased
C. not affected - ✔✔increased
Iron deficiency is second only to ______as the most prevalent nutrition problem in the USA.
A. high cholesterol
B. malnutrition
C. obesity
D. low blood pressure - ✔✔obesity
Among the trace minerals, which mineral participates as cofactors in the most enzyme systems?
A. zinc
B. iron
C. selenium
D. copper - ✔✔zinc
What two minerals can cause oxidative damage to cells when in their free ion forms?
A. zinc and copper
B. iron and zinc
C. copper and iron
D. None of above - ✔✔copper and iron
Which mineral is an essential cofactor in the action of glutathione peroxidase (GPX) in the reduction of
organic peroxides and hydrogen peroxide?A. zinc
B. iron
C. copper
D. selenium - ✔✔selenium
Excess dietary iron can decrease copper absorption.
A. True
B. False - ✔✔true
Keshan disease is associated with ______deficiency.
A. zinc
B. copper
C. selenium
D. iron - ✔✔selenium
Water Soluble Vitamins - ✔✔B vitamins and vitamin C
B Vitamins - ✔✔Thiamin (B1), Riboflavin (B2), Niacin (B3), Biotin (B7), Pantothenic Acid (B5), Vitamin B6,
Folic Acid, Vitamin B12
Fat Soluble Vitamins - ✔✔Vitamins A, D, E, K
Vitamins are.. - ✔✔Organic compounds that are required in the diet in only small amounts to maintain
fundamental functions of the body (growth, metabolism, cellular integrity, etc.).
Small Amounts of Vitamins - ✔✔distinguish from macronutrients because vitamins don't provide energy
and don't use for structure
Organic - ✔✔distinguishes from minerals that are required in small amounts but inorganic natureThe activity of a vitamin is often found in several closely related compounds known as.. - ✔✔vitamers
Some of vitamins are not Strictly Dietary Essentials - ✔✔Niacin (from tryptophan) and Vitamin D (from
7-dehydrocholesterol upon sunlight) can be made in the human body
Biotin and Vitamin K can be made, at least in part, by bacteria in the large intestine
Multivitamin-mineral Use as Dietary Supplements - ✔✔About one half of US population and 70% of
adults ≥71 y use dietary supplements (33% are multivitamins & multiminerals):
- >$21 billion spent annually reported in 2006
- ~4% increase yearly since 2000
- Early use by children and adolescents for sport performance
Do we really need supplements? - ✔✔No overall benefits from taking multivitamin/mineral on mortality
and incidence of chronic diseases such as cancer or heart disease
Some studies showed increased risk of cancers
Characteristics of Water Soluble Vitamins - ✔✔Apart from their solubility characteristics, the water
soluble vitamins have little in common from the chemical point of view
Because of their water solubility:
- excesses of these vitamins are excreted in urine
- rarely accumulate in toxic concentrations
- their storage is limited (except for cobalamin) and must be provided regularly
Function of Water Soluble Vitamins - ✔✔The function of vitamins are varied, but the most common
function for Vitamin Bs, C, and reduced K is required as coenzymes or components of coenzymes.Coenzymes are defined as small, organic molecules that are required by an enzyme and that participate
in the chemistry of catalysis.
- e.g.: Ascorbic acid, biotin, NAD, NADP, FAD, FMN, thiamin pyrophosphate, folate coenzymes, methylB12, Co-A, etc
Vitamin C - ✔✔also called ascorbic acid (AA)
Ascorbic acid can be synthesized from glucose
Humans & primates, guinea pigs etc. are unable to synthesize AA due to genetic mutation
Sources: fruits and vegetables (~80-90% AA & 10-20% DHAA) 2
Digestion, Absorption, and Transfer of Vitamin C - ✔✔- AA is absorbed via sodium-dependent active
transport in the small intestine
- DHAA is absorbed via passive diffusion or glucose transporters
- AA exits the enterocyte to the liver via portal vein, then to extrahepatic tissues
Bioavailability of Vitamin C - ✔✔Bioavailability is defined as the proportion of the compound
administered intravenously that appears in plasma over time when compared with the compound
administrated orally.
Bioavailability represents the proportion of the compound that is absorbed from GI tract.
Vitamin C bioavailability is nearly 100% for dose between 15-200 mg, which declines for higher doses
(~50% for 1250 mg)Metabolism and Excretion of Vitamin C - ✔✔Kidneys can reabsorb AA or DHAA that depends on plasma
AA concentrations
AA metabolites (DHAA, diketogulonate, oxalic acid etc.) and excess AA are excreted in urine if plasma
level is higher than renal threshold.
Renal threshold: plasma level at
0.8-1.4 mg/dL or
body pool at 1,500 mg or
dietary 100 mg daily
RDA for Vitamin C - ✔✔Males --> 90
Females --> 75
Pregnancy --> 100
Lactation -->120
Smokers --> Additional +35
Dietary Reference Intake (DRI) - ✔✔In the US, DRIs are usually set up by US Food and Nutrition Board
(FNB): Dietary Reference Intakes Subcommittee
In addition, the Institute of Medicine (National Academy of Sciences, USA) installed a Standing
Committee on the Scientific Evaluation of Dietary Reference Intakes
Recommended dietary allowance (RDA) • Adequate intake (AI) • Tolerable upper intake level (UL) •
Estimated average requirement (EAR)
Recommended Dietary Allowance (RDA) - ✔✔DRA or AI is adequate to meet the known nutrient needs
of practically all healthy persons.
The determination of adequacy is difficult dependent on the functional outcome chosen:
• multiple functions of each nutrient• bioavailability, distribution, metabolism, excretion
• variation of requirements (children, elderly, gender, race, etc)
• Interaction with other nutrients or factors
Tolerable Upper Intake Level (UL) - ✔✔UL is the concept of Safety versus Risk
Traditional models are animal models to setup an acceptable daily intake (ADI) and then extrapolate noobserved-adverse-effect-level from animal to human
Collagen Synthesis (Vitamin C) - ✔✔- AA is utilized for hydroxylation of proline and lysine residues of achains of procollagen
- AA functions as a reduced agent for the reduction of iron from Fe3+ to Fe2+.
- Hydroxyproline plays a role in the formation of the triple helix of collagen, which is utilized for
connective tissues in bone, cartilage and blood vessel, etc.
Neurotransmitter Synthesis (Vitamin C) - ✔✔AA is utilized in the synthesis of norepinephrine from
dopamine
AA is also utilized for the synthesis of serotonin from tryptophan
Bile Acid Synthesis (Vitamin C) - ✔✔AA is required for the hydroxylation of cholesterol via 7-ahydroxylase, a ratelimiting step of bile acid synthesis
Carnitine Synthesis (Vitamin C) - ✔✔AA is involved in two reactions required for the synthesis of
carnitine
Sufficient production of carnitine is of significance in fat metabolismNonenzymatic Reductive Function (Vitamin C) - ✔✔aka - antioxidant
As an electron donor to reduce free radicals AA may defense against oxidant damage
Oxidative damage in DNA has been postulated to cause gene mutation and then attribute to aging and
cancer, etc.
Oxidative damage in LDL (lipid peroxidation) has been postulated to accelerate atherosclerosis -->
Coronary heart disease (CHD)
Oxidative damage in proteins has been linked to develop cataract
Vitamin C and Coronary Heart Disease - ✔✔AA has been shown to inhibit metal-catalyzed LDL oxidation
in vitro, but the effect in vivo is unknown.
Several large prospective cohort studies (the Nurses' Health Study, the Health Professionals Follow-up
Study, and the Iowa Women's Health Study) have not found a link between high AA intake and reduced
risk of heart disease
Vitamin C and Cancer - ✔✔Lab tests in animals have shown AA inhibits tumor growth and reduces
genetic damage caused by carcinogens.
Studies on eating habits of large groups of people show that a high intake of AA-rich foods may reduce
the risk of cancers at mouth, stomach, lung & pancreas.
The mechanisms of anticancer by antioxidant in vivo are not clear.
Vitamin C and Eye Health - ✔✔A 1997 study of women in Harvard's Nurses' Health Study found that AA
supplements for over 10 years greatly reduced the risk of cataracts
Long term use of AA supplements was associated with a reduced risk of age-related lens damageVitamin C and Colds - ✔✔In 1970s, Nobel prize-winning chemist Dr. Pauling proposed that a very high
intake of AA could protect against cold
However, 18 studies published have shown that AA supplements had no effect on cold incidence
Scurvy - ✔✔Intake < 10 mg daily may result in scurvy
Most notable symptoms include bleeding gums, skin discolorations, impaired wound and fracture
healing, joint pain, loose and decaying teeth, etc.
Scurvy is rare in the U.S., but poor diets with alcoholism or drug abuse may cause deficient
Vitamin C Toxicity - ✔✔Relatively nontoxic
Intake above 1 g per day may cause nausea and diarrhea
High dose > 1 g/day may induce renal stones (oxalic acid)
Thiamin (B1) - ✔✔1st recognized in 1896, determined as vital amine in 1912 and discovered the
structure in 1936
Biologically active form is Thiamin diphosphate (TDP) or thiamin pyrophosphate (TPP) Pyrimidine
Thiazole ring thiaminase
Food Sources of Thiamin - ✔✔enriched grain products
meats, especially pork
nutsDigestion, Absorption, Transport & Storage of Thiamin - ✔✔TDP is digested into free form before
absorption
Low concentrations of thiamin is absorbed into enterocyte via Na+-K+-pump, but high conc. is via
passive diffusion
Within liver, ATP donates phosphate to thiamin --> TDP --> extrahepatic tissues
50% of thiamin in body is contained in muscle tissue
Metabolism and Excretion of Thiamin - ✔✔At least 50 metabolites have been reported to occur in the
urine
Major metabolites are thiamin acetic acid, 2- methyl-4-amino-5- formylaminomethylpyrimidine, etc
Thiamin Functions - ✔✔Coenzyme for several decarboxylation reactions in carbohydrate catabolism.
Important in ATP synthesis and acetyl CoA production (--> synthesis of fatty acids, ketone bodies and
cholesterol)
Coenzyme for transketolase in pentose phosphate pathway that
- a means of generating NADPH for fatty acid synthesis
- essential for synthesis of ribose (nucleic acid)
Thiamin Deficiency - ✔✔Beriberi (can't can't)
- Dry beriberi: characterized by muscle weakness
- Wet beriberi: characterized by heart failure
Thiamin deficiency is rare in the U.S. since grains are supplemented with thiaminDeficiency may occur due to alcoholics
- Alcohol prevents thiamin uptake and utilization
Riboflavin (B2) - ✔✔Riboflavin = ribose + flavus (Latin for yellow)
Synthesized in all plants and microorganisms, but not in humans & higher organisms
Food Sources of Riboflavin - ✔✔milk and dairy products
meats, especially organ meats, and eggs
broccoli, spinach, mushrooms
fortified, ready to eat breakfast cereals
Digestion, Absorption, Transport & Storage of Riboflavin - ✔✔Riboflavin attached to proteins is freed by
stomach HCl and gastric/intestinal enzymatic hydrolysis
FAD and FMN are further digested to free riboflavin prior to absorption
Free riboflavin is absorbed in enterocyte via a sodium-dependent carrier
Riboflavin can be circulated to the liver via portal vein
In liver, some riboflavin is phosphorylated into FMN and FAD
Free riboflavin can be circulated from liver to extrahepatic tissues via blood binding proteins such as
albumin, immunoglobulins, etc.
Free riboflavin passes most cell membranes by a carrier-mediated process
Brain cells uptake FAD through a high-affinity transport system, so that FAD in brain does not decline
even during riboflavin deficiencyWithin cells, riboflavin is converted to FMN and FAD that prevent diffusion out of tissue
Metabolism and Excretion of Riboflavin - ✔✔Free riboflavin is a primary metabolite found in urine (60-
70%)
Urinary excretion of riboflavin may be noticeable a couple of hours following oral ingestion
Urinary excretion of flavins reflects dietary intake (biomarker for intervention studies)
Riboflavin Functions - ✔✔FAD & FMN are donors or acceptors of hydrogen and electrons in many
oxidationreduction reactions
• Krebs cycle
• B-oxidation of fatty acids
Into electron transport chain to produce 2ATP
FMN is a component of the electron transport chain
FADH2 is used in the formation of the active form of folate
FAD is required for conversion of tryptophan to niacin
FMN is important in B6 function
Riboflavin Deficiency and Toxicity - ✔✔Riboflavin deficiency can be severe
-Growth is stunted & skin lesions appear
- Clinical features:
• Cheilosis: cracks on the outside of the lips• Glossitis: inflammation of the tongue
• Hyperemia: redness of the oral cavity
No incidences have been reported of toxicity
Niacin (B3) - ✔✔aka - nicotinic acid
The word niacin sometimes is used as the generic name for both Nicotinic acid & Nicotinamide
Active niacin is Nicotinamide Adenine Dinucleotide (NAD+) and Nicotinamide Adenine Dinucleotide
Phosphate (NADP+)
Nicotinic acid is the form required for the synthesis of NAD + and NADP +, therefore, any dietary
nicotinamide must 1st undergo deamination to nicotinic acid
Tryptophan also may serve as a precursor for synthesis of NAD + and NADP + (60 1, required FAD and
PLP)
Niacin equivalent (NE) = 1 mg niacin or 60 mg tryptophan
Food Sources of Niacin - ✔✔meat, poultry, fish
peanuts
enriched grain products
Niacin in Foods - ✔✔Widely distributed in plant & animal origin
Niacin in some plant foods (corn, wheat & sorghum etc.) is bound to carbohydrates or peptides that are
not readily bioavailable (<10-30%)
Corn-based diets have also low tryptophan content, which may cause niacin deficiencySorghum diets also contain high levels of leucine that may inhibit niacin synthesis from tryptophan
Digestion, Absorption, Transport & Storage of Niacin - ✔✔Glycohydrolase converts NAD + or NADP +
into nicotinamide before absorption
Absorption into enterocyte is via active sodium dependent pump for low concentrations, but passive
diffusion for high concentrations
Niacin can be utilized in enterocyte or transported to liver
Converted to NAD + or NADP + in liver or circulated to extrahepatic tissues
Metabolism and Excretion of Niacin - ✔✔Little loss of niacin into urine when intake is modest, because
both nicotinic acid & nicotinamide may be reabsorbed
Primary metabolites are N'- methynicotinamide or N'-methynicotinic acid
Niacin Functions - ✔✔NAD+ or NADP+ is donors or acceptors of hydrogen and electrons
NAD+ or NADP+ is required by about 200 enzymes (most are dehydrogenases)
Most of the NADH is used to transfer electrons to the electron transport chain --> 3ATP
Most of the NADPH is used in synthesis of cholesterol, fatty acids, deoxynucleotides & steroid hormones
NADPH is also used to reduce DHAA to AA
Niacin Deficiency - ✔✔Deficiency results in a syndrome called Pellagra [Italian pelle (skin) + agra (rough)]
4Ds: dermatitis, diarrhea, dementia & deathNiacin Toxicity - ✔✔Nicotinic acid is prescribed in gram as a drug to lower blood cholesterol in
hypercholesterolemia or hypertriglyceridemia
Pharmacological doses may cause heart abnormalities, GI problem, hot flashes, skin irritations & liver
damage
UL = 35 mg/day
Pantothenic Acid (B5) - ✔✔Pantothenic acid (vitamin B5)or pantothenate (Greek: pantos means
everywhere)
Widely distributed in all plant and animal foods ( deficiency is unlikely)
Pantothenic acid is typically used to synthesize CoA & acyl carrier protein (ACP)
Food Sources of Pantothenic Acid - ✔✔meat, fish, poultry
milk and yogurt
legumes and whole grain cereals
Digestion, Absorption, Transport & Storage of Pantothenic Acid - ✔✔CoA is hydrolyzed to pantothenic
acid before absorption by enterocyte
Low conc. are absorbed by a sodium-dependent active process, high conc. are via passive diffusion
Most of the pantothenic acid in blood is found in red blood cells
Heart, muscle & liver cells take up by Na+- dependent active transport, but nervous, adipose & renal
uptake is via passive diffusionMetabolism and Excretion of Pantothenic Acid - ✔✔CoA is dephosphorylated and through a series of
subsequent reactions --> pantothenic acid
Pantothenic acid is excreted as such primarily in urine
Urinary excretion is thought to reflect dietary intake
AI for Pantothenic Acid - ✔✔5 mg/day
AI is used instead of RDA when there are insufficient data available to establish RDA
Constituent of Coenzyme A (Pantothenic Acid) - ✔✔Pyruvate dehydrogenase complex
Reacts with oxaloacetate to form citrate in Krebs
Makes ketone bodies in liver
Makes fatty acids & cholesterol
Binds with fatty acids to start B-oxidation
Constituent of Coenzyme ACP - ✔✔Acyl carrier in the synthesis of fatty acids
Pantothenic Acid Functions - ✔✔Both oxidation and synthesis of fats utilize acetylCoA.
However, the acetyl-CoA in fat synthesis exists in cytosol that is bound to the enzyme complex with
malonyl-CoA.
The enzyme, acetyl-CoA carboxylase (ACC), is the major site of regulation of fatty acid synthesis.ACC requires a biotin co-factor
Pantothenic Acid Deficiency - ✔✔Very rare and only in cases of severe malnutrition.
Symptoms of a pantothenic acid deficiency include burning feet syndrome (a feeling of tingling and
tenderness in the feet), headache, fatigue, and a sensation of weakness.
No reports of pantothenic acid toxicity
Biotin (B7) - ✔✔Biotin was once referred to as vitamin H
Within many foods, biotin is bound to protein as biocytin or biotinyllysine
Active form is as biocytin occurred in four carboxylases
The protein avidin in raw egg white binds biotin and prevents intestinal absorption --> deficiency
Intestinal flora produces a small amount of biotin
Biotin Food Sources - ✔✔Widely distributed in foods such as liver, soybeans, egg yolk, cereals & nuts,
etc
Digestion, Absorption, Transport & Storage of Biotin - ✔✔Proteins that contain biotin --> biocytin -->
free biotin for absorption by enterocyte via Na + - dependent process
High dose of biotin is absorbed via passive diffusion - 80% of biotin is free in the blood, but some are
bound by proteins
Bioavailability of biotin is variable from 100% in corn to near 0% in wheatBiotin appears to be stored, at least to a minor degree, in muscle, brain & liver
Metabolism and Excretion of Biotin - ✔✔Biotin metabolites in urine include free biotin, bisnorbiotin,
biotin sulfone & biotin sulfoxide, etc
Biotin Deficiency - ✔✔Raw egg white (avidin) --> binding biotin & preventing absorption
Inflammatory bowel disease --> inhibiting bacterium growth --> inhibiting biotin synthesis
AI of Biotin - ✔✔30 ug/day
AI is used instead of RDA when there are insufficient data available to establish RDA
Vitamin B6 - ✔✔Vitamin B6 appears in the body in six chemical forms that are interchangeable
Active form is Pyridoxal phosphate (PLP)
Pyridoxine (PN) or pyridoxine phosphate (PNP) is found
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