FNDH 620 EXAM 3 QUESTIONS & ANSWERS
PQ: When water-soluble vitamins are consumed in excess of body needs, generally the
excess is: - Answers :excreted in urine
PQ: Vitamin C acts as a coenzyme by maintaining iron in a reduced state in : - Answers
:collagen synthesis
PQ: T/F As little as 10 mg/day of vitamin C may be enough to prevent scurvy. - Answers
:True
What is a vitamin? - Answers :an organic compound required by diet in small amounts
to maintain fundamental functions of body (growth, metabolism, cellular integrity etc)
Fat soluble vitamins - Answers :Vitamins A, D, E, K
water soluble vitamins - Answers :B vitamins and vitamin C
Which vitamins can be synthesized in the body? - Answers :Niacin (from tryptophan) &
vitamin D (from 7-dehydrocholesterol upon sunlight)
Biotin & Vitamin K can be made (in part) by bacteria in large intestine
Properties of water soluble vitamins - Answers :-excess excreted in urine
- rarely accumulate to toxic concentrations
- storage is limited (except cobalamin) and must be provided regularly
Vitamin C acts as an - Answers :antioxidant and enzyme cosubstrate (coenzyme)
Vitamin C bioavailability... - Answers :almost 100% for doses btw 15-200 mg/day but
declines for higher doses (eg ~50% for 1,250 mg/day)
Ascorbic Acid absorption - Answers :via Na-dependent active transport in small intestine
dehydroascorbic acid (oxidized form of AA) absorption - Answers :via passive diffusion
or glucose transporters
RDA for vitamin C (mg/day) - Answers :- males: 90
- females: 75
- pregnancy: 100
- lactating: 120
- smokers: add'l 35
Vitamin C role in collagen synthesis - Answers :reduces iron Fe3+ -> Fe2+ to
hydroxylate proline and glycine
Vitamin C role in neurotransmitter synthesis - Answers :- norepinephrine from dopamine
,- serotonin from tryptophan
Vitamin C role in bile acid sythesis - Answers :hydroxylation of cholesterol via 7-alpha-
hdyroxylase (rate-limiting step)
Vitamin C role in carnitine synthesis - Answers :- involved in 2 reactions
Antioxidants are - Answers :Organic molecules and reducing agents that help protect
the body from harmful chemicals called free radicals
Vitamin C supplementation and chronic disease: - Answers :- coronary heart disease:
no known risk reduction in vivo
- cancer: may reduce risk of some cancers
- eye health: reduce risk of cataracts
- common cold: no effect
Vitamin C deficiency - Answers :Scurvy (bleeding gums)
PQ: A major role of thiamin is: - Answers :energy transformation
PQ: Why may alcoholism cause thiamin deficiency? - Answers :prevents uptake and
utilization
PQ: Riboflavin is required for - Answers :- formation of active folate
- converting tryptophan to niacin
- function of B6
Forms of Thiamin (B1) - Answers :thiamin diphosphate (TDP) and active form thiamin
triphosphate (TPP)
Sources of thiamin - Answers :enriched grains, pork, nuts
At low concentration B1 is absorbed into enterocyte - Answers :via Na+/K+ pump
At high concentration B1 is absorbed into enterocyte - Answers :via passive diffusion
What happens to B1 in the liver? - Answers :ATP donates a phosphate to TDP -> TPP
and then circulated to extrahepatic tissues
Where is about 50% of B1 stored in the body? - Answers :The muscle
B1 excretion - Answers :Urine: reported more than 50 metabolites
Thiamin/B1 function - Answers :- coenzyme for decarboxylation reactions in CHO
catabolism
, - important for ATP synthesis and acetyl-CoA production -> synthesis of FAs, ketone
bodies, cholesterol
- coenzyme for transketolase in the pentose phosphate pathway (means of generating
NADPH for FA synthesis)
Thiamin Deficiency - Answers :Beriberi (wet: heart failure/dry: muscle weakness)
Riboflavin (B2) sources - Answers :dairy products, meats, eggs, leafy greens,
mushrooms fortified cereal
Brain cells uptake: - Answers :FAD through high-affinity transport system so FAD in
brain does not decline during deficiency
Urinary excretion of flavus: - Answers :reflects dietary intake and is a biomarker used in
intervention studies (yellow color)
B2 deficiency - Answers :cheilosis; glossitis; corneal vascularity
PQ: T/F Nicotinamide, but not nicotinic acid, is the form required for the synthesis of
nicotinamide adenine dinucleotide. - Answers :False
PQ: How are recommended intakes of niacin expressed (units)? - Answers :Niacin
equivalents
PQ: List 4 water-soluble vitamins that are required by pyruvate dehydrogenase
complex. - Answers :Thiamin (B1), Riboflavin (B2), Niacin (B3), Pantothenic acid (B5)
How many mg of tryptophan = 1 mg niacin? - Answers :60 mg tryptophan = 1 mg niacin
(niacin equivalent)
Niacin (B3) sources - Answers :Liver, nuts, legumes
Why is niacin is some plant foods on 10-30% bioavailable? - Answers :Bound to
CHO/peptides
Corn: low in tryptophan
Sorghum: high levels of leucine inhibits niacin synthesis from tryptophan
Niacin absorption at low concentratins - Answers :via Na+ dependent pumps
Niacin absorption at high concentrations - Answers :via passive diffusion
PQ: T/F Absorption of biotin is near 0% from wheat. - Answers :True
What is corn's bioavailability of biotin? - Answers :100%
What was biotin once referred to as? - Answers :Vitamin H
PQ: When water-soluble vitamins are consumed in excess of body needs, generally the
excess is: - Answers :excreted in urine
PQ: Vitamin C acts as a coenzyme by maintaining iron in a reduced state in : - Answers
:collagen synthesis
PQ: T/F As little as 10 mg/day of vitamin C may be enough to prevent scurvy. - Answers
:True
What is a vitamin? - Answers :an organic compound required by diet in small amounts
to maintain fundamental functions of body (growth, metabolism, cellular integrity etc)
Fat soluble vitamins - Answers :Vitamins A, D, E, K
water soluble vitamins - Answers :B vitamins and vitamin C
Which vitamins can be synthesized in the body? - Answers :Niacin (from tryptophan) &
vitamin D (from 7-dehydrocholesterol upon sunlight)
Biotin & Vitamin K can be made (in part) by bacteria in large intestine
Properties of water soluble vitamins - Answers :-excess excreted in urine
- rarely accumulate to toxic concentrations
- storage is limited (except cobalamin) and must be provided regularly
Vitamin C acts as an - Answers :antioxidant and enzyme cosubstrate (coenzyme)
Vitamin C bioavailability... - Answers :almost 100% for doses btw 15-200 mg/day but
declines for higher doses (eg ~50% for 1,250 mg/day)
Ascorbic Acid absorption - Answers :via Na-dependent active transport in small intestine
dehydroascorbic acid (oxidized form of AA) absorption - Answers :via passive diffusion
or glucose transporters
RDA for vitamin C (mg/day) - Answers :- males: 90
- females: 75
- pregnancy: 100
- lactating: 120
- smokers: add'l 35
Vitamin C role in collagen synthesis - Answers :reduces iron Fe3+ -> Fe2+ to
hydroxylate proline and glycine
Vitamin C role in neurotransmitter synthesis - Answers :- norepinephrine from dopamine
,- serotonin from tryptophan
Vitamin C role in bile acid sythesis - Answers :hydroxylation of cholesterol via 7-alpha-
hdyroxylase (rate-limiting step)
Vitamin C role in carnitine synthesis - Answers :- involved in 2 reactions
Antioxidants are - Answers :Organic molecules and reducing agents that help protect
the body from harmful chemicals called free radicals
Vitamin C supplementation and chronic disease: - Answers :- coronary heart disease:
no known risk reduction in vivo
- cancer: may reduce risk of some cancers
- eye health: reduce risk of cataracts
- common cold: no effect
Vitamin C deficiency - Answers :Scurvy (bleeding gums)
PQ: A major role of thiamin is: - Answers :energy transformation
PQ: Why may alcoholism cause thiamin deficiency? - Answers :prevents uptake and
utilization
PQ: Riboflavin is required for - Answers :- formation of active folate
- converting tryptophan to niacin
- function of B6
Forms of Thiamin (B1) - Answers :thiamin diphosphate (TDP) and active form thiamin
triphosphate (TPP)
Sources of thiamin - Answers :enriched grains, pork, nuts
At low concentration B1 is absorbed into enterocyte - Answers :via Na+/K+ pump
At high concentration B1 is absorbed into enterocyte - Answers :via passive diffusion
What happens to B1 in the liver? - Answers :ATP donates a phosphate to TDP -> TPP
and then circulated to extrahepatic tissues
Where is about 50% of B1 stored in the body? - Answers :The muscle
B1 excretion - Answers :Urine: reported more than 50 metabolites
Thiamin/B1 function - Answers :- coenzyme for decarboxylation reactions in CHO
catabolism
, - important for ATP synthesis and acetyl-CoA production -> synthesis of FAs, ketone
bodies, cholesterol
- coenzyme for transketolase in the pentose phosphate pathway (means of generating
NADPH for FA synthesis)
Thiamin Deficiency - Answers :Beriberi (wet: heart failure/dry: muscle weakness)
Riboflavin (B2) sources - Answers :dairy products, meats, eggs, leafy greens,
mushrooms fortified cereal
Brain cells uptake: - Answers :FAD through high-affinity transport system so FAD in
brain does not decline during deficiency
Urinary excretion of flavus: - Answers :reflects dietary intake and is a biomarker used in
intervention studies (yellow color)
B2 deficiency - Answers :cheilosis; glossitis; corneal vascularity
PQ: T/F Nicotinamide, but not nicotinic acid, is the form required for the synthesis of
nicotinamide adenine dinucleotide. - Answers :False
PQ: How are recommended intakes of niacin expressed (units)? - Answers :Niacin
equivalents
PQ: List 4 water-soluble vitamins that are required by pyruvate dehydrogenase
complex. - Answers :Thiamin (B1), Riboflavin (B2), Niacin (B3), Pantothenic acid (B5)
How many mg of tryptophan = 1 mg niacin? - Answers :60 mg tryptophan = 1 mg niacin
(niacin equivalent)
Niacin (B3) sources - Answers :Liver, nuts, legumes
Why is niacin is some plant foods on 10-30% bioavailable? - Answers :Bound to
CHO/peptides
Corn: low in tryptophan
Sorghum: high levels of leucine inhibits niacin synthesis from tryptophan
Niacin absorption at low concentratins - Answers :via Na+ dependent pumps
Niacin absorption at high concentrations - Answers :via passive diffusion
PQ: T/F Absorption of biotin is near 0% from wheat. - Answers :True
What is corn's bioavailability of biotin? - Answers :100%
What was biotin once referred to as? - Answers :Vitamin H
