Exam 2, niacin

Question 1

properties of niacin

Answer 1

stable to heat, light, acid, alkali, oxidation (REALLY STABLE)

Question 2

niacin structure

Answer 2

basically a single hexose ring with
-COOH

Question 3

riboflavin structure looks like

Answer 3

3 hexose in line then a chain sticking up

Question 4

thiamin structure looks like

Answer 4

one hexose and one pentose together with methylene bridge

Question 5

niacin coenzymes

Answer 5

NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate)

Question 6

what is NAD’s job

Answer 6

removal and transfer of electrons from metabolic intermediates to ETC -> ATP

Question 7

what is NADP’s job

Answer 7

reducing agent for biosynthetic pathways (fatty acid, cholesterol and steroid hormone synthesis)

Question 8

digestion of niacin

Answer 8

-NAD and NADP are broken down in enterocyte to free nicotinamide
-nictotinamide and nicotinic acid absorbed in stomach and SI
-then nicotinamide enters blood and once in cells can be reverted to coenzyme form

Question 9

toxicity of riboflavin

Answer 9

no known toxicity

Question 10

what is the MAIN function of niacin

Answer 10

accepts + transfers H ions in ENERGY METABOLISM

Question 10

what is one reason why niacin is essential in the body (popular)

Answer 10

> 400 enzymes require NAD and NADP as H donor/ acceptor

Question 11

oxidative functions using NAD

Answer 11

-decarboxylation of pyruvate
-oxidation of Acetyl CoA in 3 places of krebs
-B oxidation of fatty acid

Question 12

what other 3 “extra” pathways is NADPH used in

Answer 12

1. glucose to monophosphate shunt
2. regeneration of antioxidants
3. oxidation of ethanol

Question 13

NADPH works with FAD in the…

Answer 13

activation of glutathione reductase which restores glutathione (reducing it)

Question 14

when people are going to drink they sometimes take?

Answer 14

B vitamins, they supposedly help with the metabolization of alcohol

Question 15

main niacin defficiency- 4D’s (and how is one seen in dogs)

Answer 15

1. dermatitis (pellagra and black tongue in dogs)
2. diarrhea
3. dementia
4. death

Question 16

Joseph Goldberger

Answer 16

-public health doctor, 1915
-worked with prisoners where corn was a staple with foods like cornbread for example
-changed their diet to healthier, more varied, more nutrients
-realized pellagra was not an infection, it was a deficiency

Question 17

difference between cornbread = deficiency and corn tortillas not *

Answer 17

-in cornbread, niacin is bound to protein which means its not free to be absorbed
-in corn tortillas, the nixtamalization process leads to alkaline hydrolysis which cuts the bonds and frees niacin for absorption

Question 18

photograph: person with spots on lower half o f face and tongue sticking out

Answer 18

pellagra: niacin deficiency

Question 19

photograph: dry scaly skin in legs and elbows down

Answer 19

pellagra: niacin deficiency

Question 20

photograph: scaly, even bleeding elbows

Answer 20

pellagra: niacin deficiency

Question 21

photograph: skin affected only in collar

Answer 21

Casal’s collar, characteristic of pellagra: niacin deficiency, and occurs when affected skin is exposed to the sun so the dermatitis becomes more prevalent/visible in those areas

Question 22

photograph: cracked feet before and after

Answer 22

pellagra : niacin deficiency

Question 23

photograph: poultry that has it’s wings up (feather abnormalities/ behavior change)

Answer 23

dermatitis: niacin deficiency

Question 24

photo: big chicken compared with little chicken of the same age

Answer 24

niacin deficiency

Question 25

what is used to assess niacin status

Answer 25

urinary metabolites, serum/RBC NAD: NADP ratio

Question 26

niacin toxicity symptoms

Answer 26

-liver dysfunction and damage
-blurred vision & edema of eyes
-glucose intolerance
-gout
-flushing

Question 27

when does toxicity of niacin ocurr

Answer 27

UL: 35 mg/ day

Question 28

photo: man before and after with skin normal and then red

Answer 28

flushing: niacin toxicity

Question 29

what was niaicn supplementation used for in the past and why is it not anymore?

Answer 29

before statins existed it was used to lower LDL cholesterol levels and increase HDL, yet there was no proven decrease of heart disease

Question 30

RDI niacin

Answer 30

M: 16 mg, F: 14 mg

Question 31

main food source for niacin

Answer 31

chicken breast (all proteins in general)

Question 32

why should niacin NOT be taken as a supplement *

Answer 32

-excess niacin is metabolized to 2PY and 4PY metabolites
-4PY activates inflammatory pathways
-explains heart thing, contraproducente

Question 33

Explain and give examples of the differing roles of NAD and NADP as coenzymes in energy metabolism
and biosynthesis. *

Answer 33

NAD works as an electron carrier in metabolic pathways while NADP works in biosynthetic pathways (like fatty acid/ cholesterol/ steroid / antioxidant synthesis)