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Nutrient Metabolism > Test 3 > Flashcards

Test 3 Flashcards

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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
Renal threshold of vitamin C
-plasma level at 0.8-1.4 mg/dL -body pool at 1500 mg -dietary 100 mg daily
26
Ascorbic Acid acts as an electron donor for how many mammalian enzymes?
at least 8
27
Enzymes that require ascorbic acid either have ____ or ___ activity.
Monooxygenase or dioxygenase
28
How does vitamin C function in collagen synthesis?
AA is utilized for hydroxylation of proline and lysine residues of alpha-chains of procollagen
29
***Vitamin C acts as a coenzyme by maintaining iron in a reduced state in:
collagen synthesis
30
Vitamin C in neurotransmitter synthesis:
-synthesis of norepinephrine from dopamine -synthesis of serotonin from tryptophan
31
Vitamin C in bile acid synthesis
-required for the hydroxylation of cholesterol via 7-alpha-hydroxylase, a rate limiting step of bile acid synthesis
32
Vitamin C deficiency
Scurvy -<10 mg daily for months
33
*** As little as 10 mg/day of Vitamin C may be enough to prevent scurvy.
True
34
Biologically active form of Thiamin
thiamin diphosphate or thiamin pyrophosphate (same same)
35
Food sources of thiamin
enriched grain products, meats (especially pork), nuts
36
Thiamin is digested into _______ before absorption
Free form
37
Low concentrations of thiamin is absorbed into enterocyte via High concentrations....
Na+-K+ pump -passive diffusion
38
Within liver, ____ donates phosphate to thiamin to make it TDP (active state)
ATP
39
50% of thiamin in body is contained in _____
muscle tissue
40
Thiamin is coenzyme for
decarboxylation reactions in carbohydrate catabolism
41
***A major role for thiamin is:
energy transformation
42
Thiamin deficiency
Beriberi
43
Dry Beriberi
characterized by muscle weakness
44
Wet beriberi
characterized by heart failure
45
***Deficiency of thiamin may occur in alcoholics because...
alcohol prevents thiamin uptake and utilization
46
Riboflavin can be degraded by ____ or ____.
light or acid
47
Food sources of Riboflavin
milk and dairy meats (especially organ) eggs broccoli, spinach, mushrooms fortified, ready-to-eat breakfast cereals
48
Which two enzymes take FAD to FMN to riboflavin
FAD pyrophosphatase FMN phosphatase
49
Does the brain ever experience riboflavin (B2) deficiency?
No bc brain cells uptake FAD through a high-infinity transport system so that FAD does not decline even during riboflavin deficiency
50
What is the primary metabolite found in urine?
Free riboflavin (60-70%)
51
Function of Riboflavin
FAD & FMN (as coenzymes) are donors or acceptors of hydrogen and electrons in many redox reaction -Krebs cycle - beta-oxidation of fatty acids
52
How is B2 related to folate?
FADH2 is used in the formation of active folate
53
_____ is required for conversion of tryptophan to niacin
FAD
54
How is B2 related to B6 function?
FMN is important in B6 function
55
***Riboflavin in required for:
-formation of active folate -conversion of tryptophan to niacin -function of B6
56
Riboflavin deficiency
-can be severe -stunted growth and skin lesions appear
57
Clinical features of riboflavin deficiency:
-cheilosis-cracks on the outside of lips -glossitis-inflammation of the tongue -hyperemia-redness of the oral cavity
58
Active niacin...
NAD+ and NADP+
59
What form of B3 is required for the synthesis of NAD+ and NADP+
Nicotinic acid
60
Dietary _____ must first undergo deamination to nicotinic acid
nicotinamide
61
Niacin equivalent
1 mg niacin or 60 mg tryptophan
62
***T/F Nicotinamide, but not nicotinic acid, is the form required for the synthesis of nicotinamide adenine dinucleotide
False
63
Food sources of Niacin
Meat, poultry, and fish peanuts enriched grain products
64
_________ converts NAD+ or NADP+ into nicotinamide before absorption
glycohydrolase
65
NAD+ or NADP+ is required by about ______ enzymes
200
66
Most of the NADH is used to...
transfer electrons to the electron transport chain -> 3 ATP
67
Most of the NADPH is used in....
synthesis of cholesterol, fatty acids, deoxynucleotides, and steroid hormones
68
Niacin (B3) deficiency
Pellagra (rough skin)
69
4D of Niacin deficiency
dermatitis, diarrhea, dementia, death
70
Toxicity of Niacin
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
71
***How are the recommended intakes of niacin expressed (units)?
niacin equivalents (mgs)
72
B5
Pantothenic Acid
73
Food sources of pantothenic acid
meat, fish, poultry milk and yogurt legumes and whole-grain cereals
74
Pantothenic acid is typically used to synthesize _______ and _______
CoA and acyl carrier protein (ACP)
75
Pantothenic Acid Deficiency
burning feet syndrome, headache, fatigue, sensation of weakness
76
***List four water soluble vitamins that are required by pyruvate dehydrogenase complex.
-pantothenic acid -thiamin (B1) -niacin -riboflavin
77
Vitamin H
Biotin
78
Food sources of biotin
liver soybeans egg yolk cereals/nuts
79
Active form of biotin
biocytin
80
How many carboxylases is biocytin found?
Four
81
The protein _____ in raw egg white binds to biotin and prevents intestinal absorption
avidin -can lead to deficiency
82
_______ can produce a small amount of biotin
Intestinal flora
83
Route of biotin to enterocyte...
proteins that contain biotin ->biocytin ->free biotin for absorption by enterocyte
84
Biotin is taken up by the enterocyte via
Na+ dependent process (requires ATP) for regular amounts -high amounts via passive diffusion
85
_____% of biotin is free in the blood, but some are bound by protein
80%
85
_____% of biotin is free in the blood, but some are bound by protein
80%
86
Bioavailability is variable from _____% in corn to nearly _____% in wheat
100%; 0%
87
Where is biotin stored
muscle, brain, liver
88
***Bioavailability of biotin is near 0% from wheat.
True
89
***Intake of raw egg white may cause deficiency of...
biotin
90
Biotin is coenzyme in these 4 enzymes
-Pyruvate carboxylase -Acetyl-CoA carboxylase -Propionyl-CoA carboxylase -beta-methylcrotonyl CoA carboxylase
91
Vitamin B6 is a group of chemicals....
6 chemical forms that are interchangeable
92
The most common active form of B6
Pyridoxal 5'-Phosphate (PLP)
93
What form of B6 is found in plant foods?
Pyridoxine (PN) or phyridoxine phosphate (PNP)
94
What form of B6 is found in animal products?
Pyrodoxal (PL) and pyridoxamine (PM)
95
Vitamin B6 must be dephosphorylated prior to absorption T/F
true
96
Primary absorption method of B6
passive diffusion
97
Once in the enterocyte B6 is re-phosphorylated
true
98
Bioavailability of biotin
>90%
99
B6 activation requires ______
riboflavin -riboflavin deficiency may interfere with B6 metabolism
100
Where is 75%-89% of B6 found?
muscle tissue
101
How many enzymes does PLP serve as coenzyme for?
>100
102
Functions of PLP
-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
***Which of the following is one of the main functions of vitamin B6?
-transamination
104
B6 deficiency
hypochromic microcytic anemia
105
B6 toxicity
pharmaceutical dose (1-6 g/day) sensory and peripheral neuropathy -intake of >500 mg
106
folic acid: folate:
-oxidized form in fortified form or supplements -reduced form naturally in foods
107
Most folate found in portal circulation
N^5 methyl THF
108
Most folate in liver
THF and N^5 methyl THF
109
Folic acid functions
methionine cycle
110
Methionine cycle
-occur in cytosol -extensive folate metabolism occurs in mitochondria -interconversion of serine and glycine requires PLP containing enzyme (SHMT)
111
****Methionine cycle requires
-B6 -B12 -Folate -Niacin (all water soluble)
112
Folic Acid Deficiency
-birth defects -megaloblastic anemia -cancer -hyperhomocysteinemia and vascular disease
113
***Which anemia is related to folate deficiency?
Megaloblastic
114
***To protect against birth defects, a higher RDA of folic acid has been suggested for pregnant women
True
115
Cobalamins
B12
116
Which type of anemia can B12 deficiency cause?
megaloblastic
117
B12 consists of a group of compounds called
corrinoids
118
Active forms of cobalamin
methylcobalamin, adenosylcobalamin
119
***B12 can only be found in...
animal products
120
In stomach, cobalamin can be attached to _____
Intrinsic factor (IF)
121
IF-cobalamin is absorbed in ____ via _____
ileum; B12 receptor (recognizes the IF)
122
Cobalamin is rebound by ____ that is circulated to the liver
TC-II
123
In the liver, free cobalamin can be stored for _______
Years -has lowest RDA requirements b/c of this
124
B12 is excreted via ____ and ____
bile (mostly) and urine
125
Whole body turnover of B12
0.1% daily
126
B12 function
-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
L-methylmalonyl CoA mutase
L-methylmalonyl CoA to Succinyl CoA *required for synthesis of heme *important role in metab. of odd chain fatty acids
128
*** Why is the RDA of vitamin B12 so low?
-can be stored in liver for years -little B12 in the body is degraded -whole body turnover is about 0.1% daily
129
B12 deficiency
-usually due to inadequate absorption not intake -megaloblastic anemia ("methyl trap" of folic acid) -neuropathy -high homocysteine->risk of heart disease
130
High dietary folate may cure megaloblastic anemia caused by:
folate deficiency, B12 deficiency
131
Fat soluble vitamins are similar to lipids b/c...
-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
provitamin A carotenoids can be converted to ____
retinoids
133
beta carotene conversion ratio
1/12
134
alpha-carotene or beta-cryptoxanthin conversion ration
1/24
135
****Formation of retinol from beta-carotene requires the presence of what B vitamin?
Niacin
136
____ or ____ helps Vitamin A and carotenoid absorption
meal fat or oil
137
________ ________ as well as ________ can diminish carotenoid absorption
Fiber intake (especially pectin); excessive vitamin E
138
*** Dietary fat is not very important regarding the digestion and absorption of pre and provitamin A forms
False
139
Most retinol is stored as _______ in _____
retinyl esters in the liver
140
Vitamin A functions
-vision -cellular differentiation -growth -reproduction -bone development -immune system actions
141
_____ is bound to _____ to form rhodopsin in rod cells
cis-retinal and Opsin
142
Rhodopsin is needed to see....
black and white as well as to see at night
143
***Within the nucleus, retinoic acid binds to
retinoid X receptors (also retinoic acid receptors)
144
Ergocalciferol
D2
145
Cholecalciferol
D3
146
Vitamin D form synthesized by plants
D2
147
Vitamin D form synthesized by humans from cholesterol in the skin
D3
148
How much sun exposure is enough to prevent deficiencies
10 minutes
149
***About ____% of vitamin D3 is absorbed from the diet
50% via passive diffusion
150
Where is Vitamin D metabolized?
Liver
151
***circulation form of D3
calcidiol
152
biological half life of calcidiol
3 weeks
153
D3 in kidneys becomes
Calcitriol (3 hydroxy groups)
154
Active form of Vitamin D
calcitriol
155
1,25(OH)2D3
Calcitriol
156
Vitamin D functions
-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
***The vitamin D receptor is a member of the super family of nuclear receptors that regulates gene expression.
True
158
Calcitriol acts with _______ hormone to affect intestine, bone, and kidney
parathyroid (PTH)
159
Other Vitamin D functions
-modulation of neuromuscular and immune function -reduction of inflammation -modulate genes that regulate cell proliferation, differentiation, and apoptosis -prevents rickets and osteoporosis
160
Vitamin E exists as _____ and ____ with each having 4 isomers (8 total)
tocopherol and tocotrienol
161
_______ is most active form of Vitamin E
alpha-tocopherol
162
______ are free in foods, but ______ are esterified
Tocopherols, tocotrienols
163
only ___________ is resecreted back into the blood via VLDLs
alpha-tocopherol
164
Where is most vitamin E (over 90%)?
adipose tissue
165
***What is the principle transport vehicle for vitamin E in the blood?
-lipoproteins
166
Vitamin E function
-antioxidant, immune function, DNA repair
167
***Which mechanism has been proposed but not proven as vitamin E's principle function against disease prevention?
-Anti-oxidation
168
vitamin E toxicity
risk of bleeding in high doses
169
***For which vitamin is the tolerable upper limit set b/c of increased tendency for bleeding?
E
170
K1
Phylloquinone-found in green plants
171
K2
menaquinones- from bacteria
172
***What is the chemical name for vitamin K in green plants?
pylloquinone
172
***What is the chemical name for vitamin K in green plants?
pylloquinone
173
Where is vitamin k stored?
primarily in the liver
174
Vitamin K functions
-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
***As coenzyme, vitamin K is required in the carboxylation of Gla proteins by converting glutamate residues to gamma-carboxyglutamate residues?
True
176
How does Warfarin stop clotting
-inhibits epoxide reductase and Vitamin K reductase in the Vitamin K cycle
177
How many proteins have Gla domains
14
178
What 3 processes do Gla proteins regulate?
-blood coagulation -bone metabolism -vascular biology
179
Blood Clotting cascade
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
***Vitamin K deficiency is most often observed in
-newborns
181
Macrominerals
-4% of total body weight; about 25-1400 g in body
182
Macrominerals
Ca, Ph, Mg, Na, K, Cl, S
183
Most abundant macromineral
Ca (40% of total mineral mass)
184
***Which food group contributes the most calcium to our diet?
dairy
185
How much dietary calcium is absorbed?
20-50%
186
Blood Ca levels are tightly regulated and enhanced by_____ and _____, but decreased by ______.
PTH, calcitriol calcitronin
187
PTH targets bone to stimulate _____ and depress _____ to release ionized Ca into blood
osteoclasts, osteoblasts (forming bone)
188
***The primary function of parathyroid hormone (PTH) is:
-to enhance blood calcium levels by taking calcium from bone
189
Phosphorus
6th most abundant element by weight -2nd mineral after Ca
190
70% of phosphorus circulates in the blood as ___
phospholipids
191
***Name two minerals that are part of the bone crystal, hydroxyapatite:
Calcium, phosphorus
192
Which mineral is a component of ATP and creatine phosphate?
phosphorus
193
Which mineral is a component of ATP and creatine phosphate?
phosphorus
194
Is Sodium an intra or extracellular cation?
Extracellular
195
How much Na is absorbed
95%
196
3 Na transport systems
-sodium/glucose co-transport -sodium/chloride co-transport -sodium channels
197
What hormone regulates plasma levels of Na?
aldosterone
198
Does aldosterone increase or decrease reabsorption of sodium in the kidney?
increases
199
Which of the following amounts comes closest to the level of sodium typically consumed in our daily diets?
2-3 g/day
200
Potassium is regulated by ____
aldosterone
201
Aldosterone has what effect on potassium
promotes excretion
202
***All of the following are true about potassium except:
-it increases blood pressure
203
***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.
-increased
204
Which two enzymes can oxidize iron to Fe3+ so that it can bind to transferrin?
Hephaestin and ceruloplasmin
205
Which two enzymes can oxidize iron to Fe3+ so that it can bind to transferrin?
Hephaestin and ceruloplasmin
206
Primary storage form of iron in cells
ferritin
206
Primary storage form of iron in cells
ferritin
207
***Iron deficiency is second only to _____ as the most prevalent nutrition problem in the US
obesity
208
***Iron deficiency is second only to _____ as the most prevalent nutrition problem in the US
obesity
209
Zn is a cofactor for _____ enzymes
over 200
210
***Among the trace minerals, which mineral participates as cofactors in the most enzyme systems?
zinc
211
Zinc fingers...how many transcription factors require zinc
2000
212
Bioavailability of copper
50%
213
***Excess dietary iron can decrease copper absorption.
True
214
What two minerals can cause oxidative damage to cells when in their free ion forms?
copper and iron
215
**Which mineral is an essential cofactor in the action of glutathione peroxidase (GPX) in the reduction of organic peroxides and hydrogen peroxide?
selenium
216
Keshan disease is associated with _____ deficiency
Selenium

Nutrient Metabolism (2 decks)

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