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Nutrient Metabolism > Test 3 > Flashcards

Test 3 Flashcards

1
Q

Water-Soluble Vitamins

A

C, Thiamin, Riboflavin, B6, B12, Folate, Biotin, Niacin, Pantothenic Acid

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2
Q

Fat-Soluble Vitamins

A

A, D, E, K

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3
Q

Water soluble

A

excrete via urine

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4
Q

Fat-soluble

A

goes through liver, bile duct, intestines, then excreted through feces

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5
Q

Thiamin

A

B1

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6
Q

Riboflavin

A

B2

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7
Q

Niacin

A

B3

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8
Q

Vitamin

A

Organic compounds that are required in the diet in only small amounts to maintain fundamental functions of the body

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9
Q

B6 is composed of what 3 compounds

A

pyridoxine, pyridoxal, pyridoxamine

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10
Q

Some vitamins are not strictly dietary essential:

A

ex: Vitamin D(cholesterol), Niacin (tryptophan), Biotin and vitamin K can be made in part by bacteria in large intestine

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11
Q

Can water soluble vitamins accumulate in toxic concentrations?

A

Rarely

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12
Q

Water soluble vitamins storage is limited and must be provided regularly, except for…

A

T; cobalamin (B12)

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13
Q

***When water soluble vitamins are consumed in excess of body needs, generally the excess is

A

Excreted in the urine

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14
Q

Most common function of water-soluble functions…

A

coenzymes or components of coenzymes

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15
Q

Ascorbic Acid

A

Vitamin C

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16
Q

Vitamin C is made from _____ in plants

A

glucose

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17
Q

Oxidized vitamin C becomes

A

Dehydroascorbic Acid (DHAA)
-it can serve as an antioxidant

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18
Q

Which form of vitamin C is anti-oxidant

A

ascorbic

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19
Q

Five servings of fruits and vegetables a day can provide how much Vitamin C?

A

Approx. 200 mg

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20
Q

How is ascorbic acid absorbed?

A

via sodium-dependent active transport in the SI

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21
Q

DHAA is absorbed how?

A

passive diffusion or glucose transporters

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22
Q

Bioavailability

A

represents the proportion of the compound that is absorbed from the GI tract

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23
Q

Vitamin C bioaviilability

A

Nearly 100% for dose between 12-200mg, which declines for higher doses (~50% for 1250 mg)

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24
Q

Excess AA are excreted in urine if plasma level is

A

HIgher than renal threshold

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25
Q

Renal threshold of vitamin C

A

-plasma level at 0.8-1.4 mg/dL
-body pool at 1500 mg
-dietary 100 mg daily

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26
Q

Ascorbic Acid acts as an electron donor for how many mammalian enzymes?

A

at least 8

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27
Q

Enzymes that require ascorbic acid either have ____ or ___ activity.

A

Monooxygenase or dioxygenase

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28
Q

How does vitamin C function in collagen synthesis?

A

AA is utilized for hydroxylation of proline and lysine residues of alpha-chains of procollagen

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29
Q

***Vitamin C acts as a coenzyme by maintaining iron in a reduced state in:

A

collagen synthesis

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30
Q

Vitamin C in neurotransmitter synthesis:

A

-synthesis of norepinephrine from dopamine
-synthesis of serotonin from tryptophan

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31
Q

Vitamin C in bile acid synthesis

A

-required for the hydroxylation of cholesterol via 7-alpha-hydroxylase, a rate limiting step of bile acid synthesis

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32
Q

Vitamin C deficiency

A

Scurvy
-<10 mg daily for months

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33
Q

*** As little as 10 mg/day of Vitamin C may be enough to prevent scurvy.

A

True

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34
Q

Biologically active form of Thiamin

A

thiamin diphosphate or thiamin pyrophosphate (same same)

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35
Q

Food sources of thiamin

A

enriched grain products, meats (especially pork), nuts

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36
Q

Thiamin is digested into _______ before absorption

A

Free form

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37
Q

Low concentrations of thiamin is absorbed into enterocyte via

High concentrations….

A

Na+-K+ pump

-passive diffusion

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38
Q

Within liver, ____ donates phosphate to thiamin to make it TDP (active state)

A

ATP

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39
Q

50% of thiamin in body is contained in _____

A

muscle tissue

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40
Q

Thiamin is coenzyme for

A

decarboxylation reactions in carbohydrate catabolism

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41
Q

***A major role for thiamin is:

A

energy transformation

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42
Q

Thiamin deficiency

A

Beriberi

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43
Q

Dry Beriberi

A

characterized by muscle weakness

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44
Q

Wet beriberi

A

characterized by heart failure

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45
Q

***Deficiency of thiamin may occur in alcoholics because…

A

alcohol prevents thiamin uptake and utilization

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46
Q

Riboflavin can be degraded by ____ or ____.

A

light or acid

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47
Q

Food sources of Riboflavin

A

milk and dairy
meats (especially organ)
eggs
broccoli, spinach, mushrooms
fortified, ready-to-eat breakfast cereals

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48
Q

Which two enzymes take FAD to FMN to riboflavin

A

FAD pyrophosphatase
FMN phosphatase

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49
Q

Does the brain ever experience riboflavin (B2) deficiency?

A

No bc brain cells uptake FAD through a high-infinity transport system so that FAD does not decline even during riboflavin deficiency

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50
Q

What is the primary metabolite found in urine?

A

Free riboflavin (60-70%)

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51
Q

Function of Riboflavin

A

FAD & FMN (as coenzymes) are donors or acceptors of hydrogen and electrons in many redox reaction
-Krebs cycle
- beta-oxidation of fatty acids

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52
Q

How is B2 related to folate?

A

FADH2 is used in the formation of active folate

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53
Q

_____ is required for conversion of tryptophan to niacin

A

FAD

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54
Q

How is B2 related to B6 function?

A

FMN is important in B6 function

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55
Q

***Riboflavin in required for:

A

-formation of active folate
-conversion of tryptophan to niacin
-function of B6

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56
Q

Riboflavin deficiency

A

-can be severe
-stunted growth and skin lesions appear

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57
Q

Clinical features of riboflavin deficiency:

A

-cheilosis-cracks on the outside of lips
-glossitis-inflammation of the tongue
-hyperemia-redness of the oral cavity

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58
Q

Active niacin…

A

NAD+ and NADP+

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59
Q

What form of B3 is required for the synthesis of NAD+ and NADP+

A

Nicotinic acid

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60
Q

Dietary _____ must first undergo deamination to nicotinic acid

A

nicotinamide

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61
Q

Niacin equivalent

A

1 mg niacin or 60 mg tryptophan

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62
Q

***T/F Nicotinamide, but not nicotinic acid, is the form required for the synthesis of nicotinamide adenine dinucleotide

A

False

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63
Q

Food sources of Niacin

A

Meat, poultry, and fish
peanuts
enriched grain products

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64
Q

_________ converts NAD+ or NADP+ into nicotinamide before absorption

A

glycohydrolase

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65
Q

NAD+ or NADP+ is required by about ______ enzymes

A

200

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66
Q

Most of the NADH is used to…

A

transfer electrons to the electron transport chain -> 3 ATP

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67
Q

Most of the NADPH is used in….

A

synthesis of cholesterol, fatty acids, deoxynucleotides, and steroid hormones

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68
Q

Niacin (B3) deficiency

A

Pellagra (rough skin)

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69
Q

4D of Niacin deficiency

A

dermatitis, diarrhea, dementia, death

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70
Q

Toxicity of Niacin

A

Nicotinic acid is prescribed in grams as a drug to lower blood cholesterol
–may cause heart abnormalities, hot flashes, skin irritations, liver damages….

UL = 35 mg/day

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71
Q

***How are the recommended intakes of niacin expressed (units)?

A

niacin equivalents (mgs)

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72
Q

B5

A

Pantothenic Acid

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73
Q

Food sources of pantothenic acid

A

meat, fish, poultry
milk and yogurt
legumes and whole-grain cereals

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74
Q

Pantothenic acid is typically used to synthesize _______ and _______

A

CoA and acyl carrier protein (ACP)

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75
Q

Pantothenic Acid Deficiency

A

burning feet syndrome, headache, fatigue, sensation of weakness

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76
Q

***List four water soluble vitamins that are required by pyruvate dehydrogenase complex.

A

-pantothenic acid
-thiamin (B1)
-niacin
-riboflavin

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77
Q

Vitamin H

A

Biotin

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78
Q

Food sources of biotin

A

liver
soybeans
egg yolk
cereals/nuts

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79
Q

Active form of biotin

A

biocytin

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80
Q

How many carboxylases is biocytin found?

A

Four

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81
Q

The protein _____ in raw egg white binds to biotin and prevents intestinal absorption

A

avidin
-can lead to deficiency

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82
Q

_______ can produce a small amount of biotin

A

Intestinal flora

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83
Q

Route of biotin to enterocyte…

A

proteins that contain biotin ->biocytin ->free biotin for absorption by enterocyte

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84
Q

Biotin is taken up by the enterocyte via

A

Na+ dependent process (requires ATP) for regular amounts

-high amounts via passive diffusion

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85
Q

_____% of biotin is free in the blood, but some are bound by protein

A

80%

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85
Q

_____% of biotin is free in the blood, but some are bound by protein

A

80%

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86
Q

Bioavailability is variable from _____% in corn to nearly _____% in wheat

A

100%; 0%

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87
Q

Where is biotin stored

A

muscle, brain, liver

88
Q

***Bioavailability of biotin is near 0% from wheat.

A

True

89
Q

***Intake of raw egg white may cause deficiency of…

A

biotin

90
Q

Biotin is coenzyme in these 4 enzymes

A

-Pyruvate carboxylase
-Acetyl-CoA carboxylase
-Propionyl-CoA carboxylase
-beta-methylcrotonyl CoA carboxylase

91
Q

Vitamin B6 is a group of chemicals….

A

6 chemical forms that are interchangeable

92
Q

The most common active form of B6

A

Pyridoxal 5’-Phosphate (PLP)

93
Q

What form of B6 is found in plant foods?

A

Pyridoxine (PN) or phyridoxine phosphate (PNP)

94
Q

What form of B6 is found in animal products?

A

Pyrodoxal (PL) and pyridoxamine (PM)

95
Q

Vitamin B6 must be dephosphorylated prior to absorption T/F

A

true

96
Q

Primary absorption method of B6

A

passive diffusion

97
Q

Once in the enterocyte B6 is re-phosphorylated

A

true

98
Q

Bioavailability of biotin

A

> 90%

99
Q

B6 activation requires ______

A

riboflavin

-riboflavin deficiency may interfere with B6 metabolism

100
Q

Where is 75%-89% of B6 found?

A

muscle tissue

101
Q

How many enzymes does PLP serve as coenzyme for?

A

> 100

102
Q

Functions of PLP

A

-AA metabolism
-glycogen metabolism (required by glycogen phosphorylase)
-synthesis of heme (could lead to anemia)
-required for synthesis of niacin from tryptophan (both FAD & PLP)
-methionine cycle
-homocysteine -> cysteine

103
Q

***Which of the following is one of the main functions of vitamin B6?

A

-transamination

104
Q

B6 deficiency

A

hypochromic microcytic anemia

105
Q

B6 toxicity

A

pharmaceutical dose (1-6 g/day)
sensory and peripheral neuropathy
-intake of >500 mg

106
Q

folic acid:
folate:

A

-oxidized form in fortified form or supplements
-reduced form naturally in foods

107
Q

Most folate found in portal circulation

A

N^5 methyl THF

108
Q

Most folate in liver

A

THF and N^5 methyl THF

109
Q

Folic acid functions

A

methionine cycle

110
Q

Methionine cycle

A

-occur in cytosol
-extensive folate metabolism occurs in mitochondria
-interconversion of serine and glycine requires PLP containing enzyme (SHMT)

111
Q

**Methionine cycle requires

A

-B6
-B12
-Folate
-Niacin
(all water soluble)

112
Q

Folic Acid Deficiency

A

-birth defects
-megaloblastic anemia
-cancer
-hyperhomocysteinemia and vascular disease

113
Q

***Which anemia is related to folate deficiency?

A

Megaloblastic

114
Q

***To protect against birth defects, a higher RDA of folic acid has been suggested for pregnant women

A

True

115
Q

Cobalamins

A

B12

116
Q

Which type of anemia can B12 deficiency cause?

A

megaloblastic

117
Q

B12 consists of a group of compounds called

A

corrinoids

118
Q

Active forms of cobalamin

A

methylcobalamin, adenosylcobalamin

119
Q

***B12 can only be found in…

A

animal products

120
Q

In stomach, cobalamin can be attached to _____

A

Intrinsic factor (IF)

121
Q

IF-cobalamin is absorbed in ____ via _____

A

ileum; B12 receptor (recognizes the IF)

122
Q

Cobalamin is rebound by ____ that is circulated to the liver

A

TC-II

123
Q

In the liver, free cobalamin can be stored for _______

A

Years
-has lowest RDA requirements b/c of this

124
Q

B12 is excreted via ____ and ____

A

bile (mostly) and urine

125
Q

Whole body turnover of B12

A

0.1% daily

126
Q

B12 function

A

-cofactor for methionine synthase
-transfer of adenosine group in 2 reactions
*L-methylmalonyl-CoA mutase
-maintenance of CNS including brain and spinal chord (methionine can convert to SAM ->choline->myelin sheath)

127
Q

L-methylmalonyl CoA mutase

A

L-methylmalonyl CoA to Succinyl CoA
*required for synthesis of heme
*important role in metab. of odd chain fatty acids

128
Q

*** Why is the RDA of vitamin B12 so low?

A

-can be stored in liver for years
-little B12 in the body is degraded
-whole body turnover is about 0.1% daily

129
Q

B12 deficiency

A

-usually due to inadequate absorption not intake
-megaloblastic anemia (“methyl trap” of folic acid)
-neuropathy
-high homocysteine->risk of heart disease

130
Q

High dietary folate may cure megaloblastic anemia caused by:

A

folate deficiency, B12 deficiency

131
Q

Fat soluble vitamins are similar to lipids b/c…

A

-absorption requires bile salts
-transported by chylomicrons
-stored in liver and fatty tissue for long periods
-eliminated slowly
-generally toxic if consumed in excess

132
Q

provitamin A carotenoids can be converted to ____

A

retinoids

133
Q

beta carotene conversion ratio

A

1/12

134
Q

alpha-carotene or beta-cryptoxanthin conversion ration

A

1/24

135
Q

**Formation of retinol from beta-carotene requires the presence of what B vitamin?

A

Niacin

136
Q

____ or ____ helps Vitamin A and carotenoid absorption

A

meal fat or oil

137
Q

________ ________ as well as ________ can diminish carotenoid absorption

A

Fiber intake (especially pectin); excessive vitamin E

138
Q

*** Dietary fat is not very important regarding the digestion and absorption of pre and provitamin A forms

A

False

139
Q

Most retinol is stored as _______ in _____

A

retinyl esters in the liver

140
Q

Vitamin A functions

A

-vision
-cellular differentiation
-growth
-reproduction
-bone development
-immune system actions

141
Q

_____ is bound to _____ to form rhodopsin in rod cells

A

cis-retinal and Opsin

142
Q

Rhodopsin is needed to see….

A

black and white as well as to see at night

143
Q

***Within the nucleus, retinoic acid binds to

A

retinoid X receptors (also retinoic acid receptors)

144
Q

Ergocalciferol

A

D2

145
Q

Cholecalciferol

A

D3

146
Q

Vitamin D form synthesized by plants

A

D2

147
Q

Vitamin D form synthesized by humans from cholesterol in the skin

A

D3

148
Q

How much sun exposure is enough to prevent deficiencies

A

10 minutes

149
Q

***About ____% of vitamin D3 is absorbed from the diet

A

50% via passive diffusion

150
Q

Where is Vitamin D metabolized?

A

Liver

151
Q

***circulation form of D3

A

calcidiol

152
Q

biological half life of calcidiol

A

3 weeks

153
Q

D3 in kidneys becomes

A

Calcitriol (3 hydroxy groups)

154
Q

Active form of Vitamin D

A

calcitriol

155
Q

1,25(OH)2D3

A

Calcitriol

156
Q

Vitamin D functions

A

-calcium homeostasis
-promoting Ca absorption in the gut
-enhancing mobilization of Ca and phosphorous from bone
-maintaining adequate blood calcium and phosphate concentrations
-involving in bone mineralization w/calcitonin hormone (from thyroid)

157
Q

***The vitamin D receptor is a member of the super family of nuclear receptors that regulates gene expression.

A

True

158
Q

Calcitriol acts with _______ hormone to affect intestine, bone, and kidney

A

parathyroid (PTH)

159
Q

Other Vitamin D functions

A

-modulation of neuromuscular and immune function
-reduction of inflammation
-modulate genes that regulate cell proliferation, differentiation, and apoptosis
-prevents rickets and osteoporosis

160
Q

Vitamin E exists as _____ and ____ with each having 4 isomers (8 total)

A

tocopherol and tocotrienol

161
Q

_______ is most active form of Vitamin E

A

alpha-tocopherol

162
Q

______ are free in foods, but ______ are esterified

A

Tocopherols, tocotrienols

163
Q

only ___________ is resecreted back into the blood via VLDLs

A

alpha-tocopherol

164
Q

Where is most vitamin E (over 90%)?

A

adipose tissue

165
Q

***What is the principle transport vehicle for vitamin E in the blood?

A

-lipoproteins

166
Q

Vitamin E function

A

-antioxidant, immune function, DNA repair

167
Q

***Which mechanism has been proposed but not proven as vitamin E’s principle function against disease prevention?

A

-Anti-oxidation

168
Q

vitamin E toxicity

A

risk of bleeding in high doses

169
Q

***For which vitamin is the tolerable upper limit set b/c of increased tendency for bleeding?

A

E

170
Q

K1

A

Phylloquinone-found in green plants

171
Q

K2

A

menaquinones- from bacteria

172
Q

***What is the chemical name for vitamin K in green plants?

A

pylloquinone

172
Q

***What is the chemical name for vitamin K in green plants?

A

pylloquinone

173
Q

Where is vitamin k stored?

A

primarily in the liver

174
Q

Vitamin K functions

A

-as a coenzyme , involved in the carboxylation of certain glutamate residues in protein…located in Gla domains which can bind to Ca…-bone mineralization, blood clotting

175
Q

***As coenzyme, vitamin K is required in the carboxylation of Gla proteins by converting glutamate residues to gamma-carboxyglutamate residues?

A

True

176
Q

How does Warfarin stop clotting

A

-inhibits epoxide reductase and Vitamin K reductase in the Vitamin K cycle

177
Q

How many proteins have Gla domains

A

14

178
Q

What 3 processes do Gla proteins regulate?

A

-blood coagulation
-bone metabolism
-vascular biology

179
Q

Blood Clotting cascade

A

Factor X, Vitamin K and calcium activate to form Xa, Active Xa converts prothrombin to thrombin (IIa), IIa catalyzes soluble fibrinogen to insoluble fibrin, fibrin aggregates to form a polymer and stop bleeding

180
Q

***Vitamin K deficiency is most often observed in

A

-newborns

181
Q

Macrominerals

A

-4% of total body weight; about 25-1400 g in body

182
Q

Macrominerals

A

Ca, Ph, Mg, Na, K, Cl, S

183
Q

Most abundant macromineral

A

Ca (40% of total mineral mass)

184
Q

***Which food group contributes the most calcium to our diet?

A

dairy

185
Q

How much dietary calcium is absorbed?

A

20-50%

186
Q

Blood Ca levels are tightly regulated and enhanced by_____ and _____, but decreased by ______.

A

PTH, calcitriol
calcitronin

187
Q

PTH targets bone to stimulate _____ and depress _____ to release ionized Ca into blood

A

osteoclasts, osteoblasts (forming bone)

188
Q

***The primary function of parathyroid hormone (PTH) is:

A

-to enhance blood calcium levels by taking calcium from bone

189
Q

Phosphorus

A

6th most abundant element by weight
-2nd mineral after Ca

190
Q

70% of phosphorus circulates in the blood as ___

A

phospholipids

191
Q

***Name two minerals that are part of the bone crystal, hydroxyapatite:

A

Calcium, phosphorus

192
Q

Which mineral is a component of ATP and creatine phosphate?

A

phosphorus

193
Q

Which mineral is a component of ATP and creatine phosphate?

A

phosphorus

194
Q

Is Sodium an intra or extracellular cation?

A

Extracellular

195
Q

How much Na is absorbed

A

95%

196
Q

3 Na transport systems

A

-sodium/glucose co-transport
-sodium/chloride co-transport
-sodium channels

197
Q

What hormone regulates plasma levels of Na?

A

aldosterone

198
Q

Does aldosterone increase or decrease reabsorption of sodium in the kidney?

A

increases

199
Q

Which of the following amounts comes closest to the level of sodium typically consumed in our daily diets?

A

2-3 g/day

200
Q

Potassium is regulated by ____

A

aldosterone

201
Q

Aldosterone has what effect on potassium

A

promotes excretion

202
Q

***All of the following are true about potassium except:

A

-it increases blood pressure

203
Q

***Oral supplements of ferrous iron are available in complexes with sulfate, succinate, citrate, lactate, tartate, fumarate, or gluconate. The absorption of these nonheme iron supplements could be _____ when injested with vitamin C or other antioxidants.

A

-increased

204
Q

Which two enzymes can oxidize iron to Fe3+ so that it can bind to transferrin?

A

Hephaestin and ceruloplasmin

205
Q

Which two enzymes can oxidize iron to Fe3+ so that it can bind to transferrin?

A

Hephaestin and ceruloplasmin

206
Q

Primary storage form of iron in cells

A

ferritin

206
Q

Primary storage form of iron in cells

A

ferritin

207
Q

***Iron deficiency is second only to _____ as the most prevalent nutrition problem in the US

A

obesity

208
Q

***Iron deficiency is second only to _____ as the most prevalent nutrition problem in the US

A

obesity

209
Q

Zn is a cofactor for _____ enzymes

A

over 200

210
Q

***Among the trace minerals, which mineral participates as cofactors in the most enzyme systems?

A

zinc

211
Q

Zinc fingers…how many transcription factors require zinc

A

2000

212
Q

Bioavailability of copper

A

50%

213
Q

***Excess dietary iron can decrease copper absorption.

A

True

214
Q

What two minerals can cause oxidative damage to cells when in their free ion forms?

A

copper and iron

215
Q

**Which mineral is an essential cofactor in the action of glutathione peroxidase (GPX) in the reduction of organic peroxides and hydrogen peroxide?

A

selenium

216
Q

Keshan disease is associated with _____ deficiency

A

Selenium

Nutrient Metabolism (2 decks)

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