Water soluble vitamins Flashcards
1
Q
What type of vitamin is Vitamin C?
A
Water soluble
2
Q
What is Vitamin C’s role in health and disease?
A
Important
3
Q
Why is Vitamin C controversial?
A
Claims of curing diseases in megadoses
4
Q
What diseases has Vitamin C been claimed to cure?
A
Common cold to cancer
5
Q
What is the first known disease associated with diet?
A
Scurvy
6
Q
When was scurvy prevalent among mariners?
A
Sixteenth century
7
Q
How many mariners died from scurvy in the 16th century?
A
About 10,000
8
Q
What caused scurvy among mariners?
A
Lack of fresh vegetables
9
Q
Who published �Treatise on Scurvy�?
A
James Lind
10
Q
What year was �Treatise on Scurvy� published?
A
1753
11
Q
What did the Royal Navy start doing in 1795?
A
Supplying lime or lemon juice to crews
12
Q
What nickname did English sailors get from carrying lemons?
A
Limeys
13
Q
What type of compound is ascorbic acid?
A
Hexose derivative
14
Q
What structure does ascorbic acid resemble?
A
Monosaccharides
15
Q
What causes the acidity of vitamin C?
A
Enolic hydroxyl groups
16
Q
What is vitamin C�s chemical property?
A
Strong reducing agent
17
Q
What is formed by oxidation of L-ascorbic acid?
A
Dehydroascorbic acid
18
Q
Is the reaction between ascorbic acid and dehydroascorbic acid reversible?
A
Yes
19
Q
Which forms of vitamin C are biologically active?
A
Ascorbic acid and dehydroascorbic acid
20
Q
Which form of ascorbic acid is inactive?
A
D-ascorbic acid
21
Q
What form predominates in plasma and tissues?
A
Reduced form (ascorbic acid)
22
Q
What is the ratio of ascorbic acid to dehydroascorbic acid in tissues?
A
0.6256944444444446
23
Q
What is formed when dehydroascorbic acid is hydrated?
A
2,3-diketogulonic acid
24
Q
Is 2,3-diketogulonic acid active?
A
No
25
What promotes spontaneous hydration of dehydroascorbic acid?
Alkaline or neutral solution
26
What does hydration of dehydroascorbic acid lead to?
Biological inactivation
27
What accelerates oxidation of ascorbic acid?
Copper
28
What makes vitamin C inactive during cooking?
Use of copper vessels
29
Can all animals synthesize vitamin C?
No
30
What pathway is used for ascorbic acid synthesis in animals?
Uronic acid pathway
31
Which species cannot synthesize ascorbic acid?
Primates, guinea pigs, bats
32
What enzyme deficiency prevents vitamin C synthesis?
L-gulonolactone oxidase
33
Where is vitamin C absorbed?
Intestine
34
Is vitamin C stored significantly in the body?
No
35
How is ascorbic acid excreted?
In urine
36
Name two metabolites of ascorbic acid
Diketogulonic acid
37
What property enables most functions of vitamin C?
Reversible oxidation-reduction
38
What is vitamin C's role in collagen formation?
Coenzyme in hydroxylation of proline and lysine
39
What enzymes require vitamin C for hydroxylation?
Lysyl hydroxylase
40
What are needed for collagen hydroxylation?
Vitamin C
41
What do hydroxyproline and hydroxylysine help with?
Collagen cross-linking
42
What is vitamin C essential for in tissue repair?
Connective tissue maintenance
43
What are the components of bone tissue?
Organic collagen
44
What is vitamin C�s role in bones?
Required for bone formation
45
How does vitamin C aid iron absorption?
Keeps iron in ferrous form
46
What does vitamin C help form from iron?
Ferritin
47
How does vitamin C affect hemoglobin?
Converts methemoglobin to hemoglobin
48
What process in hemoglobin breakdown needs vitamin C?
Formation of bile pigments
49
What amino acid metabolism needs vitamin C?
Tryptophan
50
What is vitamin C�s role in serotonin synthesis?
Hydroxylation of tryptophan
51
What other amino acid needs vitamin C in its metabolism?
Tyrosine
52
What reaction in tyrosine metabolism needs vitamin C?
Oxidation of p-hydroxy phenylpyruvate
53
What is the product of the reaction in tyrosine metabolism?
Homogentisic acid
54
What vitamin�s active form needs vitamin C?
Folic acid (tetrahydrofolate)
55
What enzyme uses vitamin C in folate activation?
Folic acid reductase
56
What cells mature with help of ascorbic acid and folate?
Erythrocytes
57
What enzyme in peptide hormone synthesis needs vitamin C?
Peptidylglycine hydroxylase
58
What is hydroxylated in peptide hormone synthesis?
Terminal glycine
59
What gland has high vitamin C levels during stress?
Adrenal gland
60
What hormone synthesis requires vitamin C?
Corticosteroids
61
How does vitamin C spare other vitamins?
Acts as an antioxidant
62
Which vitamins are spared by ascorbic acid?
Vitamin A
63
How does vitamin C support immunity?
Enhances immunoglobulin synthesis
64
What eye condition does vitamin C help prevent?
Cataract
65
What chronic diseases may vitamin C help prevent?
Cancer
66
What is the adult RDA for vitamin C?
60-70 mg/day
67
How much more vitamin C is needed in pregnancy or lactation?
20-40% increase
68
Name four good dietary sources of vitamin C
Citrus fruits
69
Name three more vitamin C-rich foods
Tomatoes
70
Where is high vitamin C content found in the body?
Adrenal gland
71
Is milk a good source of vitamin C?
No
72
What disease results from vitamin C deficiency?
Scurvy
73
Name a gum symptom of scurvy
Spongy
74
What oral issue occurs in scurvy?
Loose teeth
75
What systemic symptoms are seen in scurvy?
Anemia
76
What functions are impaired in scurvy?
Immunity
77
What scientist promoted vitamin C megadoses?
Linus Pauling
78
What dose did Pauling suggest?
Up to 18 g/day
79
What is the effect of megadoses on common cold?
Reduce duration
80
What risk is associated with high vitamin C metabolism?
Kidney stones (from oxalate)
81
What is another name for Thiamine?
Anti-beri-beri or antineuritic vitamin
82
Is thiamine water or fat soluble?
Water soluble
83
What is the coenzyme form of thiamine?
Thiamine pyrophosphate (TPP)
84
Which metabolism is TPP mostly associated with?
Carbohydrate metabolism
85
What two rings make up the structure of thiamine?
Pyrimidine ring and thiazole ring
86
What connects the pyrimidine and thiazole rings in thiamine?
Methylene bridge
87
Which vitamin contains a thiazole ring naturally?
Thiamine
88
What group of thiamine is esterified to phosphate to form TPP?
Alcohol (OH) group
89
How many phosphate groups are esterified to form TPP?
2 moles
90
What enzyme catalyzes the formation of TPP from thiamine?
Thiamine pyrophosphate transferase
91
What molecule donates the pyrophosphate group for TPP formation?
ATP
92
What type of reactions is TPP involved in?
Energy releasing reactions in carbohydrate metabolism
93
Which enzyme converts pyruvate to acetyl CoA?
Pyruvate dehydrogenase
94
What coenzyme is required for pyruvate dehydrogenase?
TPP
95
Which cycle involves ?-ketoglutarate dehydrogenase?
Citric acid cycle
96
What coenzyme does ?-ketoglutarate dehydrogenase require?
TPP
97
Which enzyme in the HMP shunt requires TPP?
Transketolase
98
Which enzyme catalyzes oxidative decarboxylation of branched chain amino acids?
Branched chain ?-keto acid dehydrogenase
99
Which amino acids are involved in the branched chain decarboxylation?
Valine
100
Which coenzyme is essential for acetylcholine synthesis?
TPP
101
What role does TPP play in nerve impulse transmission?
Helps in ion translocation and acetylcholine synthesis
102
What is the RDA of thiamine for adults?
1�1.5 mg/day
103
What is the thiamine requirement per 1000 calories?
0.5 mg/1000 calories
104
What is the RDA of thiamine for children?
0.7�1.2 mg/day
105
When does thiamine requirement increase?
Pregnancy
106
Name three plant-based sources of thiamine.
Cereals
107
Where is thiamine concentrated in cereals?
Outer layer (bran)
108
What process removes 80% of thiamine from rice?
Polishing of rice
109
Does polishing affect thiamine in parboiled rice?
No
110
Name two animal sources rich in thiamine.
Pork
111
Why shouldn't cooking water be discarded?
It contains dissolved thiamine
112
What causes beri-beri?
Thiamine deficiency
113
What population is at high risk of beri-beri?
Those consuming only polished rice
114
What are early symptoms of thiamine deficiency?
Anorexia
115
What is the sensation in legs caused by thiamine deficiency?
'Pins and needles'
116
Which metabolism is impaired in thiamine deficiency?
Carbohydrate metabolism
117
What accumulates in tissues during thiamine deficiency?
Pyruvate
118
Is plasma pyruvate elevated in thiamine deficiency?
Yes
119
What is excreted in urine due to thiamine deficiency?
Pyruvate
120
Does pyruvate normally enter the brain?
No
121
What changes in thiamine deficiency allow pyruvate into the brain?
Altered blood-brain barrier
122
What condition may result from pyruvate accumulation in brain?
Polyneuritis
123
What function of TPP is lost in thiamine deficiency affecting nerves?
Transmission of nerve impulse
124
What happens to transketolase activity in thiamine deficiency?
Decreased
125
What test helps assess thiamine deficiency?
RBC transketolase activity test
126
Name the two types of adult beri-beri.
Wet beri-beri
127
Which beri-beri is associated with edema?
Wet beri-beri
128
Which beri-beri affects the heart?
Wet beri-beri
129
What are the symptoms of wet beri-beri?
Edema
130
Which beri-beri involves neurological symptoms?
Dry beri-beri
131
What happens to muscles in dry beri-beri?
Progressive weakness
132
What type of beri-beri involves mixed symptoms?
Mixed beri-beri
133
What is the cause of infantile beri-beri?
Thiamine-deficient mothers
134
What is a symptom of infantile beri-beri?
Sleeplessness
135
What condition may cause sudden death in infantile beri-beri?
Cardiac failure
136
Which syndrome is common in chronic alcoholics with thiamine deficiency?
Wernicke-Korsakoff syndrome
137
What are symptoms of Wernicke-Korsakoff syndrome?
Memory loss
138
Which enzyme in seafoods destroys thiamine?
Thiaminase
139
What does thiaminase do to thiamine?
Splits pyrimidine and thiazole rings
140
What compound in ferns is a thiamine antimetabolite?
Pyrithiamine
141
Which animals are affected by fern poisoning?
Horses and cattle
142
Name two thiamine antagonists.
Pyrithiamine
143
What coenzymes are derived from riboflavin?
FMN and FAD
144
What structure is in riboflavin�s ring system?
5,7-dimethyl isoalloxazine
145
To what sugar is riboflavin�s ring attached?
D-ribitol
146
Is riboflavin heat stable?
Yes
147
Is riboflavin light sensitive?
Yes
148
What does UV light convert riboflavin into?
Lumiflavin
149
What color does lumiflavin fluoresce?
Yellow
150
What are lactoflavin, hepatoflavin, ovoflavin?
Forms of riboflavin
151
How is FMN formed from riboflavin?
Ribitol linked to phosphate
152
How is FAD formed?
FMN + AMP from ATP
153
What is the active site in flavin coenzymes?
Isoalloxazine ring
154
What do flavin coenzymes accept?
Two hydrogen atoms
155
What are FMNH2 and FADH2?
Reduced forms of FMN and FAD
156
What are enzymes using FMN or FAD called?
Flavoproteins
157
How do flavoproteins bind coenzymes?
Tightly
158
What do metalloflavoproteins contain?
Metal atoms like iron or molybdenum
159
What metabolic processes involve FAD/FMN?
Carbohydrate
160
What is a rich source of riboflavin?
Milk
161
What symptoms indicate riboflavin deficiency?
Cheilosis
162
In whom is riboflavin deficiency common?
Alcoholics
163
What test is used to assess riboflavin deficiency?
Erythrocyte glutathione reductase activity
164
What is calactoflavin?
Riboflavin antimetabolite
165
What are the coenzymes of niacin?
NAD+ and NADP+
166
Which amino acid synthesizes niacin coenzymes?
Tryptophan
167
What disease is caused by niacin deficiency?
Pellagra
168
What does pellagra mean?
Rough skin
169
Who discovered the dietary cause of pellagra?
Goldberger
170
What foods were used in Goldberger�s experiment?
Corn meal
171
What cured pellagra in Goldberger�s study?
Dried meat or liver
172
What compound is niacin derived from?
Pyridine
173
What is the amide form of niacin called?
Niacinamide or nicotinamide
174
How much tryptophan equals 1 mg of niacin?
60 mg
175
What provides ribose phosphate and AMP in NAD+ synthesis?
PRPP and ATP
176
What group does glutamine donate in NAD+ synthesis?
Amide group
177
What happens to nicotinamide after NAD+ degradation?
Excreted as N-methylnicotinamide
178
What reaction type involves NAD+/NADP+?
Oxidation-reduction reactions
179
What is accepted by NAD+ during reduction?
Hydride ion (H-)
180
What effect does niacin have on lipolysis?
Inhibits it
181
What happens to free fatty acids with niacin?
Decreased in circulation
182
What lipoproteins are lowered by niacin?
LDL
183
What is niacin used to treat?
Hyperlipoproteinemia type IIb
184
What are side effects of niacin megadoses?
Liver damage
185
What are the three vitamers of Vitamin B6?
Pyridoxine
186
What is the chemical structure base of Vitamin B6 compounds?
Pyridine derivatives
187
How do the three forms of B6 differ?
By the functional group at carbon 4 of the pyridine ring
188
What is the functional group in pyridoxine?
Primary alcohol
189
What is the functional group in pyridoxal?
Aldehyde
190
What is the functional group in pyridoxamine?
Amine
191
Where is pyridoxamine mostly found?
In plants
192
Where are pyridoxal and pyridoxamine found?
In animal foods
193
Can pyridoxine be converted to other B6 forms?
Yes
194
Can pyridoxal and pyridoxamine form pyridoxine?
No
195
What is the active coenzyme form of Vitamin B6?
Pyridoxal phosphate (PLP)
196
How is PLP synthesized?
From pyridoxine
197
How is Vitamin B6 excreted?
As 4-pyridoxic acid in urine
198
What is PLP attached to in enzymes?
Epsilon-amino group of lysine
199
What metabolism is PLP associated with?
Amino acid metabolism
200
Which specialized products depend on pyridoxine?
Serotonin
201
Which reactions involve PLP?
Transamination
202
What is transamination?
Conversion of amino acids to keto acids
203
What enzyme carries out transamination?
Transaminase
204
Where do keto acids go after transamination?
Citric acid cycle
205
What kind of vitamin is B6 based on its role in energy?
Energy-releasing vitamin
206
What does B6 integrate metabolically?
Carbohydrate and amino acid metabolism
207
What is formed when PLP interacts with amino acids?
Schiff base
208
What is the result of PLP taking the amino group?
Pyridoxamine phosphate
209
Which neurotransmitter synthesis depends on PLP?
GABA
210
Is GABA excitatory or inhibitory?
Inhibitory
211
What amino acid is the precursor to catecholamines?
Tyrosine
212
Which catecholamines require PLP for synthesis?
Dopamine
213
What is PLP�s role in heme synthesis?
Required for ?-aminolevulinic acid synthesis
214
What coenzymes are made from tryptophan using PLP?
NAD+ and NADP+
215
Which enzyme needs PLP in niacin synthesis?
Kynureninase
216
What is excreted more in B6 deficiency?
Xanthurenic acid
217
What amino acids does PLP help metabolize?
Sulfur-containing amino acids
218
What enzyme transfers sulfur in cysteine synthesis?
Cystathionine synthase
219
What is taurine?
PLP-dependent decarboxylated product of cysteine
220
What does taurine help with?
Bile acid conjugation
221
What amino acids require PLP for deamination?
Hydroxy group-containing amino acids
222
Which enzyme synthesizes serine from glycine?
Hydroxymethyltransferase
223
What does PLP help absorb in the intestine?
Amino acids
224
What condition does B6 prevent in the kidneys?
Hyperoxaluria and stone formation
225
Which animal foods are rich in B6?
Egg yolk
226
Which plant foods are good sources of B6?
Wheat
227
What symptoms are linked to B6 deficiency?
Depression
228
What are severe symptoms of B6 deficiency?
Convulsions and peripheral neuropathy
229
What neurotransmitters are reduced in B6 deficiency?
Serotonin
230
What does B6 deficiency cause in children?
Convulsions or epilepsy
231
What type of anemia is seen in B6 deficiency?
Hypochromic microcytic anemia
232
What is a test indicator for B6 deficiency?
High xanthurenic acid in urine after tryptophan load
233
Who is most at risk for dietary B6 deficiency?
Women on oral contraceptives
234
What drug used for TB causes B6 deficiency?
Isoniazid (INH)
235
What inactive compound does isoniazid form with PLP?
Hydrazone derivative
236
What drug used in Wilson's disease interacts with PLP?
Penicillamine
237
What must be supplemented with isoniazid or penicillamine?
Pyridoxine
238
What are Vitamin B6 antagonists?
Isoniazid
239
What is a toxic effect of high B6 dose (>0.5g/day)?
Sensory neuropathy
240
What dose of B6 may cause neurological damage?
More than 200 mg/day
