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Fat Soluble Vitamins Flashcards

1
Q

What is the biologically active form of vitamin D?

A

Calcitriol (1,25-DHCC)

Calcitriol is essential for regulating plasma levels of calcium and phosphate.

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2
Q

What regulates plasma calcium levels in the body?

A

Calcitriol

Calcitriol acts at the intestine, kidney, and bone to maintain plasma calcium levels.

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3
Q

What is the normal plasma calcium level range?

A

9-11 mg/dl

This range is vital for physiological functions.

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4
Q

How does calcitriol affect the intestine?

A

Increases absorption of calcium and phosphate

Calcitriol binds to a cytosolic receptor to enhance calcium uptake.

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5
Q

What complex is formed when calcitriol binds with its receptor in intestinal cells?

A

Calcitriol-receptor complex

This complex interacts with DNA to promote the synthesis of calcium binding protein.

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6
Q

What is the role of calcitriol in bone health?

A

Stimulates calcium uptake for deposition as calcium phosphate

Calcitriol is essential for bone formation.

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7
Q

What effect does calcitriol have on the kidney?

A

Minimizes excretion of calcium and phosphate

Enhances reabsorption of these minerals.

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8
Q

What is the function of 24,25-Dihydroxycholecalciferol (24,25-DHCC)?

A

Exact function is not known

Believed to maintain calcium homeostasis when calcitriol is adequate.

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9
Q

What enzyme synthesizes 24,25-Dihydroxycholecalciferol in the kidney?

A

24-hydroxylase

This enzyme converts calcitriol to 24,25-DHCC.

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10
Q

True or False: Calcitriol acts in three different organs to regulate calcium levels.

A

True

It acts on the intestine, kidney, and bone.

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11
Q

Fill in the blank: Calcitriol acts similarly to a _______ hormone in its mechanism of action.

A

steroid

This similarity is evident in how calcitriol interacts with target tissues.

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12
Q

What happens in response to low plasma calcium concentration?

A

Calcitriol increases plasma calcium through actions in intestine, kidney, and bone

This sequence of events is crucial for maintaining calcium levels.

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13
Q

What are the four fat soluble vitamins?

A

Vitamin A, D, E, and K

These vitamins are associated with fat for their availability, absorption, and transport.

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14
Q

What is the solubility characteristic of fat soluble vitamins?

A

Soluble in fats and oils

They can also dissolve in fat solvents like alcohol and acetone.

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15
Q

Where are fat soluble vitamins stored in the body?

A

Liver and adipose tissue

They are not readily excreted in urine.

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16
Q

What can excess consumption of fat soluble vitamins lead to?

A

Accumulation and toxic effects

Particularly noted for vitamins A and D.

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17
Q

What type of compounds are all fat soluble vitamins classified as?

A

Isoprenoid compounds

Made up of one or more isoprene units.

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18
Q

What specific function does vitamin K perform?

A

Coenzyme function

It plays a crucial role in various biochemical processes.

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19
Q

What is a common characteristic of water soluble vitamins?

A

Solubility in water

They differ chemically from each other.

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20
Q

How are water soluble vitamins excreted from the body?

A

Readily excreted in urine

They are generally not toxic to the body.

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21
Q

Why must water soluble vitamins be continuously supplied in the diet?

A

They are not stored in large quantities

B12 is an exception.

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22
Q

What are common symptoms of water soluble vitamin deficiencies?

A

Dermatitis, glossitis, cheilitis, diarrhea, mental confusion, depression, malaise

Deficiencies often show overlapping symptoms.

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23
Q

Which vitamins are closely associated with neurological manifestations upon deficiency?

A

Vitamins B6 and B12

These deficiencies can lead to significant neurological issues.

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24
Q

What are vitamers?

A

Chemically similar substances with similar vitamin activity

Examples include retinol, retinal, and retinoic acid for vitamin A.

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25
What is the primary source of vitamin A?
Foods of animal origin ## Footnote Provitamin carotenes are found in plants.
26
Who is known for curing night blindness with ox liver?
Hippocrates ## Footnote This practice dates back to around 500 B.C.
27
What is the term used to include natural and synthetic forms of vitamin A?
Retinoids ## Footnote This term encompasses various biologically active molecules.
28
What is retinol?
Vitamin A alcohol containing B-ionone ring ## Footnote It has a side chain with isoprenoid units and hydroxyl group.
29
What is the structure of retinol?
Contains two isoprenoid units, four double bonds, and one hydroxyl group ## Footnote It is present in animal tissues as retinyl ester with long chain fatty acids.
30
31
32
What is retinal?
An aldehyde form obtained by the oxidation of retinol ## Footnote Retinal and retinol are interconvertible
33
What role does zinc play in relation to retinol?
It plays an important role in retinol mobilization ## Footnote Retinol is released from the liver as free retinol
34
How is retinol transported in the circulation?
By the plasma retinol binding protein (RBP) in association with pre-albumin ## Footnote The RBP complex binds to specific receptors on cell membranes
35
What is retinoic acid?
Vitamin A acid produced by the oxidation of retinal ## Footnote Retinoic acid cannot give rise to the formation of retinal or retinol
36
What is ß-Carotene and where is it found?
A provitamin A found in plant foods ## Footnote It is cleaved in the intestine to produce two moles of retinal
37
What is the efficiency of conversion of ß-Carotene to retinal in humans?
Inefficient; ß-Carotene possesses about one-sixth vitamin A activity compared to retinol ## Footnote This indicates the limited ability of the human body to convert ß-Carotene
38
What functions does vitamin A serve?
Necessary for vision, proper growth and differentiation, reproduction, and maintenance of epithelial cells ## Footnote Each form of vitamin A has been assigned specific functions
39
How are dietary retinyl esters processed in the intestine?
Hydrolysed by pancreatic or intestinal brush border hydrolases, releasing retinol and free fatty acids ## Footnote Carotenes are hydrolysed by B-carotene 15-15-dioxygenase to release retinal
40
Who first elucidated the biochemical function of vitamin A in vision?
George Wald, who won the Nobel Prize in 1968 ## Footnote The process is known as the Rhodopsin cycle or Wald's visual cycle
41
What happens to retinol in the intestinal mucosal cells?
Reesterified to long chain fatty acids and incorporated into chylomicrons ## Footnote Chylomicrons are then transferred to the lymph
42
What is the Rhodopsin cycle?
A cyclic process involving vitamin A in the process of vision ## Footnote It describes how retinol functions in visual phototransduction
43
What is the role of B-Carotene in the body?
Antioxidant ## Footnote B-Carotene is a precursor to vitamin A and serves as an antioxidant.
44
What is Retinol classified as?
Steroid hormone - growth and differentiation ## Footnote Retinol is a form of vitamin A that plays a role in growth and differentiation.
45
What is the function of Retinal?
Visual cycle ## Footnote Retinal is essential for vision, particularly in the formation of rhodopsin.
46
What is Retinyl phosphate involved in?
Glycoprotein synthesis ## Footnote Retinyl phosphate is a form of vitamin A that aids in the synthesis of glycoproteins.
47
What is the role of Retinoic acid?
Steroid hormone - growth and differentiation ## Footnote Retinoic acid is crucial for cellular growth and differentiation.
48
What types of cells are present in the retina?
Rods and cones ## Footnote Rods are responsible for dim light vision, while cones are for bright light and color vision.
49
How many rods and cones are in the human eye?
About 10 million rods and 5 million cones ## Footnote Rods are more numerous than cones in the human retina.
50
What is the primary function of rods in the retina?
Dim light vision ## Footnote Rods are sensitive to low light levels, making them essential for night vision.
51
What is the primary function of cones in the retina?
Bright light and color vision ## Footnote Cones function best in well-lit conditions and are responsible for color differentiation.
52
What is rhodopsin?
A conjugated protein present in rods ## Footnote Rhodopsin is essential for the phototransduction process in the retina.
53
What happens to 11-cis retinal when exposed to light?
Isomerizes to all-trans retinal ## Footnote This is a crucial step in the visual cycle, leading to nerve impulse generation.
54
What is the role of retinal isomerase in the visual cycle?
Converts all-trans retinal back to 11-cis retinal ## Footnote This regeneration is necessary for the continuation of the visual cycle.
55
What is dark adaptation time?
The time taken for rhodopsin to resynthesize in dim light ## Footnote This process allows vision to improve after entering a dark environment.
56
True or False: Dark adaptation time is decreased in vitamin A deficient individuals.
False ## Footnote Vitamin A deficiency increases dark adaptation time.
57
What occurs during the bleaching of rhodopsin?
Color changes from red to yellow ## Footnote Bleaching occurs rapidly upon exposure to light.
58
What is the significance of the visual cascade?
Involves biochemical changes leading to membrane hyperpolarization ## Footnote This cascade is essential for generating nerve impulses in response to light.
59
What activates cyclic GMP phosphodiesterase in the visual cascade?
Activated transducin ## Footnote Transducin activation is a key step in the signal transduction pathway for vision.
60
Fill in the blank: Rhodopsin is composed of _______ and opsin.
11-cis-retinal ## Footnote The combination of these two components is crucial for phototransduction.

Biochemistry (1 decks)

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