Chapter 9: Vitamin B3 (Niacin)

Question 1

other names:

nicotinamide acid
nicotinamide or niacinamide
pellagra-preventive factor

Answer 1

niacin b3

Question 2

niacin - chemistry

occurs in 2 forms

both of which can be utilized by man

Answer 2

niacin or nicotinic acid and niacinamide

Question 3

niacin - chemistry

converted in the body to the cofactor _____ that can exist in its phosphorylated form (NADP)

Answer 3

nicotinamide adenine dinucleotide (NAD)

Question 4

niacin - chemistry

NADP cycles between its oxidized form NAD+ and the reduced form NADH + H+

Answer 4

-

Question 5

niacin - chemistry

a white, crystalline substance that is stable in the heat, light, alkali, acid and oxidation

Answer 5

niacin

Question 6

niacin - chemistry

forms occurring in foods are NAD, NADH, NADP, and NADPH that functions as coenzymes

Answer 6

niacin

Question 7

niacin - chemistry

1 mg niacin = _____ tryptophan

Answer 7

60 mg

Question 8

niacin - absorption, transport, utilization

absorbed in the stomach but is more readily absorbed in the _____

Answer 8

small intestine

Question 9

niacin - absorption, transport, utilization

at low concentrations, the vitamin is absorbed by carrier-mediated _____

Answer 9

facilitated diffusion

Question 10

niacin - absorption, transport, utilization

at high concentrations, absorption is by _____

Answer 10

diffusion

Question 11

niacin - absorption, transport, utilization

circulated in the blood and rapidly removed by the _____ and erythrocytes and converted to NAD and NADP

Answer 11

liver

Question 12

niacin - absorption, transport, utilization

any excess niacin is excreted in the urine as _____ and _____

Answer 12

methyl nicotinamide and methyl-carboxamide

Question 13

niacin - absorption, transport, utilization

NAD can be synthesized in the _____ from the amino acid tryptophan; only about 3% of the tryptophan is converted

Answer 13

liver

Question 14

niacin - absorption, transport, utilization

NAD can be synthesized in the liver from the amino acid _____; only about 3% of the tryptophan is converted

Answer 14

tryptophan

Question 15

niacin - functions

release of energy from cho, lipid, and chon

Answer 15

-

Question 16

niacin - functions

synthesis of _____ (3) needed for dna formation

Answer 16

cho, protein, and pentoses

Question 17

niacin - functions

acts as an ____ in the breakdown of cho, fatty acids, ketones, amino acids, and alcohol

Answer 17

electron acceptor

Question 18

niacin - functions

involved in the biosynthetic reactions such as
-fatty acid synthesis
-cholesterol and steroid hormone synthesis
-glutamate synthesis
-synthesis of deoxyribonucleic acid (DNA)

Answer 18

niacin

Question 19

niacin - deficiency

individuals whose staple diet relies on untreated _____ (2) and chronic alcoholics are at risk of niacin deficiency

Answer 19

maize or barley

Question 20

niacin - deficiency

severe niacin deficiency could lead to _____

characterized by dementia, diarrhea, dermatitis, and death

early signs: muscular weakness, anorexia, indigestion, and skin eruptions

Answer 20

pellagra

Question 21

niacin - toxicity

syptoms:
-diarrhea
-heartburn
-nausea, vomiting
-ulcer irritation
-fainting, dizziness
-painful flush and rash
-itching, burning
-excessive sweating
-abnormal liver functions
-low blood pressure (BP)

Answer 21

niacin toxicity

Question 22

niacin - recommended intake

for adults (19 - >70 y/o) males

Answer 22

16 mgNE

Question 23

niacin - recommended intake

for adults (19 - >70 y/o) females

Answer 23

14 mgNE

Question 24

niacin - recommended intake

for adults (19 - >70 y/o) pregnant

Answer 24

14 mgnE +4

Question 25

niacin - recommended intake

for adults (19 - >70 y/o) lactating

Answer 25

14 mgNE +3

Question 26

niacin - recommended intake

recommended intake of niacin corresponding to an excretion of _____ that is above the minimal excretion at which deficiency symptom occurs

Answer 26

n-methyl-nicotinamide

Question 27

niacin - food sources

protein-containing foods, liver, milk, eggs, meat, poultry, fish, beans, nuts and seeds, legumes, whole grain cereals, avocado, figs, dates, prunes, are common sources of vitamin b3

Answer 27

niacin food sources

Question 28

niacin - assessment status

niacin status is assessed by measuring _____ of niacin after administering a test dose of the vitamin

Answer 28

urinary metabolism

Question 29

niacin - assessment status

2 urinary metabolites are measured and their ratio is used to measure niacin status

Answer 29

pyridine and nicotinamide

Question 30

niacin - niacin status

for all ages
deficient: ?

Answer 30

< 0.5

Question 31

niacin - niacin status

for all ages
marginal: ?

Answer 31

0.5-1.59

Question 32

niacin - niacin status

for all ages
adequate: ?

Answer 32

> 1.6