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