Kansas State University FNDH 620 Exam 3 – 2022
(COMPLETE SOLUTIONS)
When water-soluble vitamins are consumed in excess of body needs, generally the excess is:
Correct Answer: excreted in urine
Vitamin C acts as a coenzyme by maintaining iron in a reduced state in : Correct Answer:
collagen synthesis
T/F As little as 10 mg/day of vitamin C may be enough to prevent scurvy. Correct Answer: True
What is a vitamin? Correct Answer: an organic compound required by diet in small amounts to
maintain fundamental functions of body (growth, metabolism, cellular integrity etc)
Fat soluble vitamins Correct Answer: Vitamins A, D, E, K
water soluble vitamins Correct Answer: B vitamins and vitamin C
Which vitamins can be synthesized in the body? Correct Answer: 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 Correct Answer: -excess excreted in urine
- rarely accumulate to toxic concentrations
- storage is limited (except cobalamin) and must be provided regularly
Vitamin C acts as an Correct Answer: antioxidant and enzyme cosubstrate (coenzyme)
Vitamin C bioavailability... Correct Answer: almost 100% for doses btw 15-200 mg/day but
declines for higher doses (eg ~50% for 1,250 mg/day)
Ascorbic Acid absorption Correct Answer: via Na-dependent active transport in small intestine
dehydroascorbic acid (oxidized form of AA) absorption Correct Answer: via passive diffusion
or glucose transporters
RDA for vitamin C (mg/day) Correct Answer: - males: 90
- females: 75
- pregnancy: 100
- lactating: 120
- smokers: add'l 35
Vitamin C role in collagen synthesis Correct Answer: reduces iron Fe3+ -> Fe2+ to hydroxylate
proline and glycine
, Vitamin C role in neurotransmitter synthesis Correct Answer: - norepinephrine from dopamine
- serotonin from tryptophan
Vitamin C role in bile acid sythesis Correct Answer: hydroxylation of cholesterol via 7-alpha-
hdyroxylase (rate-limiting step)
Vitamin C role in carnitine synthesis Correct Answer: - involved in 2 reactions
Antioxidants are Correct Answer: Organic molecules and reducing agents that help protect the
body from harmful chemicals called free radicals
Vitamin C supplementation and chronic disease: Correct Answer: - 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 Correct Answer: Scurvy (bleeding gums)
A major role of thiamin is: Correct Answer: energy transformation
Why may alcoholism cause thiamin deficiency? Correct Answer: prevents uptake and utilization
Riboflavin is required for Correct Answer: - formation of active folate
- converting tryptophan to niacin
- function of B6
Forms of Thiamin (B1) Correct Answer: thiamin diphosphate (TDP) and active form thiamin
triphosphate (TPP)
Sources of thiamin Correct Answer: enriched grains, pork, nuts
At low concentration B1 is absorbed into enterocyte Correct Answer: via Na+/K+ pump
At high concentration B1 is absorbed into enterocyte Correct Answer: via passive diffusion
What happens to B1 in the liver? Correct Answer: ATP donates a phosphate to TDP -> TPP and
then circulated to extrahepatic tissues
Where is about 50% of B1 stored in the body? Correct Answer: The muscle
B1 excretion Correct Answer: Urine: reported more than 50 metabolites
Thiamin/B1 function Correct Answer: - coenzyme for decarboxylation reactions in CHO
catabolism
(COMPLETE SOLUTIONS)
When water-soluble vitamins are consumed in excess of body needs, generally the excess is:
Correct Answer: excreted in urine
Vitamin C acts as a coenzyme by maintaining iron in a reduced state in : Correct Answer:
collagen synthesis
T/F As little as 10 mg/day of vitamin C may be enough to prevent scurvy. Correct Answer: True
What is a vitamin? Correct Answer: an organic compound required by diet in small amounts to
maintain fundamental functions of body (growth, metabolism, cellular integrity etc)
Fat soluble vitamins Correct Answer: Vitamins A, D, E, K
water soluble vitamins Correct Answer: B vitamins and vitamin C
Which vitamins can be synthesized in the body? Correct Answer: 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 Correct Answer: -excess excreted in urine
- rarely accumulate to toxic concentrations
- storage is limited (except cobalamin) and must be provided regularly
Vitamin C acts as an Correct Answer: antioxidant and enzyme cosubstrate (coenzyme)
Vitamin C bioavailability... Correct Answer: almost 100% for doses btw 15-200 mg/day but
declines for higher doses (eg ~50% for 1,250 mg/day)
Ascorbic Acid absorption Correct Answer: via Na-dependent active transport in small intestine
dehydroascorbic acid (oxidized form of AA) absorption Correct Answer: via passive diffusion
or glucose transporters
RDA for vitamin C (mg/day) Correct Answer: - males: 90
- females: 75
- pregnancy: 100
- lactating: 120
- smokers: add'l 35
Vitamin C role in collagen synthesis Correct Answer: reduces iron Fe3+ -> Fe2+ to hydroxylate
proline and glycine
, Vitamin C role in neurotransmitter synthesis Correct Answer: - norepinephrine from dopamine
- serotonin from tryptophan
Vitamin C role in bile acid sythesis Correct Answer: hydroxylation of cholesterol via 7-alpha-
hdyroxylase (rate-limiting step)
Vitamin C role in carnitine synthesis Correct Answer: - involved in 2 reactions
Antioxidants are Correct Answer: Organic molecules and reducing agents that help protect the
body from harmful chemicals called free radicals
Vitamin C supplementation and chronic disease: Correct Answer: - 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 Correct Answer: Scurvy (bleeding gums)
A major role of thiamin is: Correct Answer: energy transformation
Why may alcoholism cause thiamin deficiency? Correct Answer: prevents uptake and utilization
Riboflavin is required for Correct Answer: - formation of active folate
- converting tryptophan to niacin
- function of B6
Forms of Thiamin (B1) Correct Answer: thiamin diphosphate (TDP) and active form thiamin
triphosphate (TPP)
Sources of thiamin Correct Answer: enriched grains, pork, nuts
At low concentration B1 is absorbed into enterocyte Correct Answer: via Na+/K+ pump
At high concentration B1 is absorbed into enterocyte Correct Answer: via passive diffusion
What happens to B1 in the liver? Correct Answer: ATP donates a phosphate to TDP -> TPP and
then circulated to extrahepatic tissues
Where is about 50% of B1 stored in the body? Correct Answer: The muscle
B1 excretion Correct Answer: Urine: reported more than 50 metabolites
Thiamin/B1 function Correct Answer: - coenzyme for decarboxylation reactions in CHO
catabolism
