Fat soluble vitamins Flashcards
1
Q
What type of vitamin is vitamin A?
A
Fat-soluble
2
Q
In which type of food is vitamin A naturally present?
A
Animal foods
3
Q
What are the plant-based precursors of vitamin A?
A
Carotenes
4
Q
Who first used ox liver to treat night blindness?
A
Hippocrates
5
Q
What term is used for natural and synthetic forms of vitamin A?
A
Retinoids
6
Q
What are the three vitamers of vitamin A?
A
Retinol, Retinal, Retinoic acid
7
Q
What is the chemical nature of retinol?
A
Primary alcohol with a ?-ionone ring
8
Q
How is retinol stored in animal tissues?
A
As retinyl esters
9
Q
Which vitamin A vitamer is an aldehyde?
A
Retinal
10
Q
Which form of vitamin A cannot be converted back into retinal or retinol?
A
Retinoic acid
11
Q
Which provitamin A is found in plants?
A
?-Carotene
12
Q
How many molecules of retinal does ?-carotene produce?
A
Two
13
Q
How does ?-carotene compare to retinol in vitamin A activity?
A
One-sixth as active
14
Q
What enzyme hydrolyzes dietary retinyl esters?
A
Pancreatic or intestinal brush border hydrolases
15
Q
What enzyme cleaves ?-carotene in the intestine?
A
?-Carotene 15,15’-dioxygenase
16
Q
How is retinol transported in the blood?
A
Bound to retinol-binding protein (RBP)
17
Q
Which mineral is essential for retinol mobilization?
A
Zinc
18
Q
What protein does retinol-RBP complex bind to on cell membranes?
A
Specific receptors
19
Q
Where does retinol exert its function?
A
Nucleus, binding to chromatin (DNA)
20
Q
Which scientist elucidated vitamin A’s role in vision?
A
George Wald
21
Q
What is another name for the Rhodopsin cycle?
A
Wald�s visual cycle
22
Q
Which type of retinal cells detect dim light?
A
Rods
23
Q
Which type of retinal cells detect bright and color vision?
A
Cones
24
Q
What is the main visual pigment in rods?
A
Rhodopsin
25
What is rhodopsin made of?
Opsin and 11-cis retinal
26
What happens to 11-cis retinal when exposed to light?
Isomerized to all-trans retinal
27
Which enzyme converts all-trans-retinal back to 11-cis retinal?
Retinal isomerase
28
Where is excess all-trans-retinal transported?
Liver
29
What is dark adaptation time?
Time taken to regain vision in dim light
30
What happens to dark adaptation time in vitamin A deficiency?
Increases
31
What is bleaching of rhodopsin?
Change of rhodopsin color from red to yellow upon light exposure
32
What is the role of cyclic GMP in vision?
Regulates Na+ channels in rod cells
33
Which protein is activated by metarhodopsin II?
Transducin
34
What enzyme degrades cyclic GMP in rod cells?
Cyclic GMP phosphodiesterase
35
What causes hyperpolarization of rod cell membranes?
Decrease in cyclic GMP levels
36
What pigments are responsible for color vision?
Porphyropsin (red), Iodopsin (green), Cyanopsin (blue)
37
How do retinol and retinoic acid function like steroid hormones?
Regulate protein synthesis, cell growth, and differentiation
38
How does vitamin A maintain healthy epithelial tissues?
Prevents keratinization
39
Which vitamin A derivative is needed for glycoprotein synthesis?
Retinyl phosphate
40
Which iron transport protein is synthesized using vitamin A?
Transferrin
41
How does vitamin A support immunity?
Maintains immune system to fight infections
42
Which biosynthetic pathway requires vitamin A?
Cholesterol synthesis
43
Which vitamin A deficiency symptom affects vision first?
Night blindness (nyctalopia)
44
What are Bitot�s spots?
White triangular plaques on the conjunctiva
45
What is keratomalacia?
Corneal degeneration leading to blindness
46
What reproductive effect does vitamin A deficiency have in males?
Sterility due to germinal epithelium degeneration
47
What happens to skin in vitamin A deficiency?
Becomes rough and dry due to keratinization
48
What is a major symptom of hypervitaminosis A?
Dermatitis, liver enlargement, bone decalcification
49
Which antioxidant role does ?-carotene play?
Reduces risk of cancer and heart disease
50
How is vitamin A dietary requirement expressed?
Retinol equivalents (RE)
51
What is the RDA of vitamin A for men?
1000 RE (3500 IU)
52
What is the RDA of vitamin A for women?
800 RE (2500 IU)
53
Which foods are the best sources of vitamin A?
Liver, egg yolk, milk, cheese, fish liver oils
54
Which vegetables are rich in ?-carotene?
Carrots, spinach, amaranthus, mango, papaya
55
What is vitamin E?
Naturally occurring antioxidant
56
Why is vitamin E called the anti-sterility vitamin?
Essential for normal reproduction in animals
57
Why is vitamin E called a 'vitamin in search of a disease'?
No specific deficiency disease in humans
58
Who isolated vitamin E compounds?
Evans and associates
59
What is the origin of the name 'tocopherol'?
Greek: tokos (childbirth), pherein (to bear), ol (alcohol)
60
How many vitamers of vitamin E exist?
Eight
61
Which vitamer of vitamin E is most active?
Alpha-Tocopherol
62
What is the chemical structure of tocopherols?
Chromane (tocol) ring with an isoprenoid side chain
63
What gives vitamin E its antioxidant property?
Chromane ring
64
Where is vitamin E absorbed?
Small intestine
65
What is needed for vitamin E absorption?
Bile salts
66
How is vitamin E transported?
Via VLDL and LDL
67
Where is vitamin E stored?
Adipose tissue, liver, muscle
68
What is the normal plasma level of tocopherol?
< 1 mg/dl
69
What is the primary function of vitamin E?
Antioxidant
70
What type of oxidations does vitamin E prevent?
Non-enzymatic oxidation of cell components
71
Which molecules does vitamin E protect from oxidation?
Unsaturated fatty acids
72
Which mineral assists vitamin E?
Selenium
73
Where is vitamin E mainly found?
Lipoproteins, fat deposits, cell membranes
74
How does vitamin E protect PUFA?
Prevents peroxidation
75
What happens to vitamin E during antioxidant activity?
Gets oxidized to quinone form
76
Why is vitamin E called a membrane antioxidant?
Maintains membrane structure and integrity
77
Which cells does vitamin E protect from hemolysis?
RBCs
78
How does vitamin E support reproduction?
Maintains germinal epithelium of gonads
79
Which enzymes' activity is increased by vitamin E?
ALA synthase, ALA dehydratase
80
What role does vitamin E play in cellular respiration?
Stabilizes coenzyme Q in the electron transport chain
81
Which vitamins does vitamin E protect from oxidation?
Vitamin A, carotenes
82
How does vitamin E help skeletal muscle?
Supports creatine storage
83
What does vitamin E enhance in the intestine?
Amino acid absorption
84
Which macromolecule synthesis requires vitamin E?
Nucleic acids
85
How does vitamin E protect the liver?
Shields against toxins like carbon tetrachloride
86
Which vitamins work with vitamin E to delay cataracts?
Vitamins A, C, Beta-Carotene
87
What diseases has vitamin E been recommended for?
Cancer, heart disease (controversial)
88
What does vitamin E prevent in LDL?
Oxidation
89
Which enzyme contains selenium and destroys free radicals?
Glutathione peroxidase
90
How do selenium and vitamin E interact?
Synergistic antioxidant action
91
How can selenium affect vitamin E requirement?
Can reduce vitamin E need and vice versa
92
How does PUFA intake affect vitamin E needs?
Higher PUFA intake increases vitamin E requirement
93
What is the RDA of vitamin E for men?
10 mg (15 IU)
94
What is the RDA of vitamin E for women?
8 mg (12 IU)
95
How much ?-tocopherol is 1 mg?
1.5 IU
96
Who requires extra vitamin E supplementation?
Pregnant and lactating women
97
Which oils are rich in vitamin E?
Wheat germ, cottonseed, peanut, corn, sunflower
98
Which animal products contain vitamin E?
Meat, milk, butter, eggs
99
How do vitamin E deficiency symptoms vary?
Different in different species
100
What reproductive issue arises in vitamin E deficiency?
Sterility
101
Which muscle disorder occurs in vitamin E deficiency?
Degenerative changes in muscle
102
What type of anemia is linked to vitamin E deficiency?
Megaloblastic anemia
103
Which nervous system issue is linked to vitamin E deficiency?
Neurological symptoms
104
How does vitamin E deficiency affect RBCs?
Increases fragility
105
Which fat-soluble vitamin is the least toxic?
Vitamin E
106
What is the highest recorded safe dose of vitamin E?
300 mg/day for 23 years
107
What is the main function of vitamin K?
Blood clotting
108
Which German word is vitamin K named after?
Koagulation
109
Which forms of vitamin K exist?
K1 (phylloquinone), K2 (menaquinone), K3 (menadione)
110
Where is vitamin K1 found?
Plants
111
Where is vitamin K2 found?
Intestinal bacteria, animals
112
What is vitamin K3?
Synthetic form
113
What type of compound is vitamin K?
Naphthoquinone derivative
114
How is vitamin K absorbed?
With fats, requires bile salts
115
How is vitamin K transported?
With LDL
116
Where is vitamin K stored?
Mainly in the liver
117
What is vitamin K's main biochemical role?
Post-translational modification of clotting factors
118
Which clotting factors depend on vitamin K?
II, VII, IX, X
119
Which amino acid is modified by vitamin K?
Glutamic acid
120
Which enzyme carries out carboxylation in clotting?
Microsomal carboxylase
121
Which anticoagulant inhibits vitamin K?
Dicumarol
122
Which synthetic anticoagulant inhibits vitamin K?
Warfarin
123
What other protein needs vitamin K for function?
Osteocalcin (bone protein)
124
What ion binds to carboxylated clotting factors?
Calcium (Ca2+)
125
How does vitamin K deficiency affect blood clotting?
Prolonged clotting time, excessive bleeding
126
Why is vitamin K deficiency rare?
Produced by gut bacteria, present in diet
127
What factors can cause vitamin K deficiency?
Bile salt deficiency, diarrhea, antibiotics
128
What is the suggested RDA for vitamin K?
70-140 �g/day
129
Which vegetables are rich in vitamin K?
Cabbage, cauliflower, spinach, tomatoes, alfalfa
130
Which animal products contain vitamin K?
Egg yolk, meat, liver, cheese, dairy
131
What does hypervitaminosis K cause?
Hemolytic anemia, jaundice (infants)
132
Which compounds act as vitamin K antagonists?
Heparin, dicumarol, bishydroxycoumarin
133
How do vitamin K antagonists work?
Block vitamin K-dependent clotting factor activation
134
What type of vitamin is Vitamin D?
Fat-soluble
135
What is the structure of Vitamin D similar to?
Sterols
136
What does Vitamin D function like?
A hormone
137
What disease is associated with Vitamin D deficiency?
Rickets
138
Who reported that UV light induces antirachitic activity in food?
Hess (1924)
139
Who isolated Vitamin D?
Angus (1931)
140
What name was given to the isolated Vitamin D?
Calciferol
141
What is Vitamin D2 also called?
Ergocalciferol
142
What is the source of Ergocalciferol?
Plants
143
What is Vitamin D3 also called?
Cholecalciferol
144
What is the source of Cholecalciferol?
Animals
145
What is the structural difference between Vitamin D2 and D3?
D2 has an additional methyl group and a double bond
146
What are Vitamin D2 and D3 referred to as?
Provitamins
147
What is the intermediate in cholesterol biosynthesis related to Vitamin D?
7-dehydrocholesterol
148
Where is 7-dehydrocholesterol converted to cholecalciferol?
Skin (dermis and epidermis)
149
What stimulates the synthesis of Vitamin D3 in the skin?
Sunlight
150
How does dark skin affect Vitamin D synthesis?
Reduces synthesis
151
Where is Vitamin D absorbed?
Small intestine
152
What is essential for Vitamin D absorption?
Bile
153
How is Vitamin D transported in the body?
Bound to plasma ?2-globulin
154
Where is Vitamin D stored?
Liver and other tissues
155
Are Vitamins D2 and D3 biologically active?
No
156
Where is Cholecalciferol first hydroxylated?
Liver
157
What is the storage and circulatory form of Vitamin D?
25-hydroxycholecalciferol (25-OH D3)
158
Where is 25-OH D3 hydroxylated to its active form?
Kidney
159
What enzyme converts 25-OH D3 to 1,25-DHCC?
1-hydroxylase
160
What is the active form of Vitamin D?
1,25-dihydroxycholecalciferol (1,25-DHCC or Calcitriol)
161
What regulates the synthesis of 1,25-DHCC?
Plasma calcium and phosphate levels
162
How does low plasma phosphate affect 1,25-DHCC synthesis?
Increases 1-hydroxylase activity
163
How does low plasma calcium affect 1,25-DHCC synthesis?
Stimulates parathyroid hormone, which activates 1-hydroxylase
164
What does Calcitriol regulate?
Plasma calcium and phosphate levels
165
Where does Calcitriol act in the body?
Intestine, kidney, bone
166
How does Calcitriol affect the intestine?
Increases calcium and phosphate absorption
167
What protein is synthesized in the intestine due to Calcitriol?
Calcium-binding protein
168
How does Calcitriol affect bones?
Stimulates calcium uptake for bone formation
169
Which hormone works with Calcitriol for calcium mobilization from bones?
Parathyroid hormone
170
How does Calcitriol affect the kidney?
Reduces calcium and phosphate excretion
171
What is another metabolite of Vitamin D?
24,25-DHCC
172
Where is 24,25-DHCC synthesized?
Kidney
173
What enzyme synthesizes 24,25-DHCC?
24-hydroxylase
174
What is the function of 24,25-DHCC?
Not well known, helps maintain calcium homeostasis
175
What is Vitamin D3 considered?
A prohormone
176
Why is Calcitriol considered a hormone?
It has specific target organs and regulates gene expression
177
What inhibits Calcitriol action?
Actinomycin D
178
What regulates Calcitriol synthesis?
Feedback mechanism
179
What is the RDA of Vitamin D?
400 IU (10 ?g cholecalciferol)
180
What is the RDA of Vitamin D in sunny countries?
200 IU (5 ?g cholecalciferol)
181
What are good dietary sources of Vitamin D?
Fatty fish, fish liver oils, egg yolk
182
Is milk a good source of Vitamin D?
No
183
How can Vitamin D be obtained?
Sunlight exposure, diet, fortified foods
184
Who is at risk of Vitamin D deficiency?
Vegetarians, alcoholics, people with liver/kidney disease, those with fat malabsorption
185
What conditions result from Vitamin D deficiency?
Rickets (children), Osteomalacia (adults)
186
What is renal rickets?
Vitamin D deficiency due to chronic kidney failure
187
How can renal rickets be treated?
Calcitriol administration
