What are vitamins classified as in terms of their role in nutrition?
Răspuns
(A)
Essential nutrients
2
Which of the following best describes Vitamin A (retinal) from a chemical perspective?
Răspuns
(B)
A compound containing a cyclohexenyl ring
3
What enzyme is responsible for breaking down β-Carotene, a Vitamin A precursor?
Răspuns
(A)
An enzyme involved in dioxygenation
4
In the intestinal lining, what cofactor is required by retinaldehyde reductase to convert retinal to retinol?
Răspuns
(A)
A form of NADPH
5
Which of the following foods is a significant source of preformed Vitamin A?
Răspuns
(A)
Dairy products, fats, and organ meats
6
The conversion between retinol and retinal necessitates the presence of a dehydrogenase or reductase, which, in turn, requires which of the following cofactors?
Răspuns
(A)
NAD or NADP
7
What is a characteristic of fat-soluble vitamins?
Răspuns
(D)
All of the above
8
What is the standard used to define one international unit of Vitamin A?
Răspuns
(A)
The activity of 0.3 µg of Vitamin A alcohol
9
At what temperature does Lumirhodopsin remain stable?
Răspuns
(D)
Below -50°C
10
In the bloodstream, how is retinol transported?
Răspuns
(A)
Bound to a specific binding protein
11
What is the typical blood serum level of vitamin A, measured in mg per 100 ml?
Răspuns
(B)
15-60
12
Which of the following is a symptom associated with a lack of vitamin A?
Răspuns
(B)
Night blindness
13
A deficiency in Vitamin A can lead to which condition?
Răspuns
(A)
Xeropthalmia
14
What is a key role that vitamin A plays in the body?
Răspuns
(D)
To maintain the integrity of epithelial tissue
15
Which visual pigment contains retinal as a key component?
Răspuns
(B)
Rhodopsin
16
In what process does retinoic acid take part?
Răspuns
(C)
Glycoprotein
17
What form of retinal results when rhodopsin is exposed to light?
Răspuns
(A)
All trans-retinal
18
The Carr-Price reaction is utilized for identifying which vitamin?
Răspuns
(A)
Vitamin A
19
The following structure represents which of the following substances?
Răspuns
(A)
Cholecalciferol
20
Under what condition is the absorption of Vitamin D enhanced?
Răspuns
(A)
Acid pH of intestine
21
Which of the following is the most active form of Vitamin D in the body?
Răspuns
(B)
1,25-Dihydroxycholecalciferol
22
What is the typical range for 25-hydroxycholecalciferol levels in a blood test, measured in ng/ml?
Răspuns
(D)
8-55
23
What is the normal range for 1,25-dihydroxycholecalciferol in the blood, expressed in pg/ml?
Răspuns
(A)
26-65
24
What is the typical concentration of 24,25-dihydroxycholecalciferol in the blood, measured in ng/ml?
Răspuns
(C)
1-5
25
Which of the following is NOT a good source of Vitamin D?
Răspuns
(C)
Milk
26
Which of the listed options contains the highest concentration of Vitamin D?
Răspuns
(A)
Fish liver oils
27
A lack of Vitamin D can lead to which of these conditions?
Răspuns
(A)
Rickets and osteomalacia
28
The biological activity of one international unit (I.U) of vitamin D is equivalent to how much cholecalciferol?
Răspuns
(A)
0.025 µg of cholecalciferol
29
What type of light causes the breakdown of the ẞ-ring of 7-dehydrocholesterol, leading to the production of cholecalciferol?
Răspuns
(C)
Ultraviolet irridation with sunlight
30
Which organs are involved in the synthesis of calcitriol?
Răspuns
(A)
Both liver and kidney
31
Which substance contains a negligible amount of Vitamin E?
Răspuns
(D)
Fish liver oil
32
What factor negatively impacts the effectiveness of tocopherols?
Răspuns
(A)
Commercial cooking
33
Increased intake of which dietary component elevates the need for vitamin E?
Răspuns
(C)
Polyunsaturated fat
34
Which mineral's demand is lowered by vitamin E?
Răspuns
(C)
Selenium
35
Which of the following is considered a key natural antioxidant?
Răspuns
(B)
Vitamin E
36
What process do tocopherols inhibit?
Răspuns
(A)
Vitamin A oxidation
37
Creatinuria is linked to a shortage of which vitamin?
Răspuns
(C)
E
38
Which scenario does NOT lead to a true or apparent lack of vitamin K?
Răspuns
(B)
Total lack of red meat in the diet
39
Where is vitamin K primarily sourced from?
Răspuns
(A)
Green leafy plants
40
What is a primary function of Vitamin A?
Răspuns
(D)
All of these
41
From which source was Vitamin K initially extracted?
Răspuns
(D)
Putrid fish meal
42
Which vitamin is produced by bacteria in the intestines?
Răspuns
(D)
K
43
Vitamin K aids in modifying blood clotting factors by serving as a helper molecule for which enzyme?
Răspuns
(A)
Carboxylase
44
Vitamin K assists in which process?
Răspuns
(A)
Gamma carboxylation of glutamic acid residue
45
An excess of Vitamin K in newborns might lead to which condition?
Răspuns
(B)
Jaundice
46
Dicoumarol counteracts the effects of which vitamin?
Răspuns
(C)
Menadione
47
For those consuming large amounts of vitamin C, what is the typical serum ascorbic acid level?
Răspuns
(A)
1-1.4 µg/100 ml
48
Which vitamin is most likely to be lacking in someone following a diet exclusively consisting of meat?
Răspuns
(C)
Vitamin C
49
Where is the highest concentration of ascorbic acid found in the human body?
Răspuns
(B)
Adrenal cortex
50
Which vitamin is essential for creating hydroxyproline (in collagen)?
