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FNDH 620 Exam 3 -Kansas State University (Questions & Answers)
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FNDH 620 Exam 3 -Kansas StateUniversity (Questions & Answers)
When water-soluble vitamins are consumed in excess of body needs,
generally the excess is: - ✔️ excreted in urine
Vitamin C acts as a coenzyme by maintaining iron in a reduced state in :
- ✔️ collagen synthesis
T/F As little as 10 mg/day of vitamin C may be enough to prevent scurvy.
- ✔️ True
What is a vitamin? - ✔️ an organic compound required by diet in
small amounts to maintain fundamental functions of body (growth,
metabolism, cellular integrity etc)
Fat soluble vitamins - ✔️ Vitamins A, D, E, K
water soluble vitamins - ✔️ B vitamins and vitamin C
Which vitamins can be synthesized in the body? - ✔️ 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 - ✔️ -excess excreted in urine
- rarely accumulate to toxic concentrations
- storage is limited (except cobalamin) and must be provided regularly
Vitamin C acts as an - ✔️ antioxidant and enzyme cosubstrate
(coenzyme)
Vitamin C bioavailability... - ✔️ almost 100% for doses btw 15-200
mg/day but declines for higher doses (eg ~50% for 1,250 mg/day)
Ascorbic Acid absorption - ✔️ via Na-dependent active transport in
small intestine
,dehydroascorbic acid (oxidized form of AA) absorption - ✔️ via
passive diffusion or glucose transporters
RDA for vitamin C (mg/day) - ✔️ - males: 90
- females: 75
- pregnancy: 100
- lactating: 120
- smokers: add'l 35
Vitamin C role in collagen synthesis - ✔️ reduces iron Fe3+ -> Fe2+
to hydroxylate proline and glycine
Vitamin C role in neurotransmitter synthesis - ✔️ - norepinephrine
from dopamine
- serotonin from tryptophan
Vitamin C role in bile acid sythesis - ✔️ hydroxylation of cholesterol
via 7-alpha-hdyroxylase (rate-limiting step)
Vitamin C role in carnitine synthesis - ✔️ - involved in 2 reactions
Antioxidants are - ✔️ Organic molecules and reducing agents that
help protect the body from harmful chemicals called free radicals
Vitamin C supplementation and chronic disease: - ✔️ - 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 - ✔️ Scurvy (bleeding gums)
A major role of thiamin is: - ✔️ energy transformation
Why may alcoholism cause thiamin deficiency? - ✔️ prevents uptake
and utilization
Riboflavin is required for - ✔️ - formation of active folate
- converting tryptophan to niacin
, - function of B6
Forms of Thiamin (B1) - ✔️ thiamin diphosphate (TDP) and active
form thiamin triphosphate (TPP)
Sources of thiamin - ✔️ enriched grains, pork, nuts
At low concentration B1 is absorbed into enterocyte - ✔️ via Na+/K+
pump
At high concentration B1 is absorbed into enterocyte - ✔️ via passive
diffusion
What happens to B1 in the liver? - ✔️ ATP donates a phosphate to
TDP -> TPP and then circulated to extrahepatic tissues
Where is about 50% of B1 stored in the body? - ✔️ The muscle
B1 excretion - ✔️ Urine: reported more than 50 metabolites
Thiamin/B1 function - ✔️ - 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 - ✔️ Beriberi (wet: heart failure/dry: muscle
weakness)
Riboflavin (B2) sources - ✔️ dairy products, meats, eggs, leafy
greens, mushrooms fortified cereal
Brain cells uptake: - ✔️ FAD through high-affinity transport system
so FAD in brain does not decline during deficiency
Urinary excretion of flavus: - ✔️ reflects dietary intake and is a
biomarker used in intervention studies (yellow color)
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