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MD1S2: Biochemistry 202 > Vitamins: Classifications and role > Flashcards

Vitamins: Classifications and role Flashcards

1
Q

What are vitamins?

A

A group of organic nutrients which are:
1) Needed in minute quantities (microgram and milligram amounts)
2) Are generally not synthesized by the body
3) Are necssary for metabolism, growth, reproduction, maintenance of tissue and aid in immune phenomena
4) Are destroyed by excessive heat, light and storage

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2
Q

What is a provitamin?

A

An inactive precursor to a vitamin

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3
Q

What are the functions of vitamins?

A

Co-enzymes in the metabolism of carbohydrates, fat and proteins (vitamin-B)
Anti-oxidants (beta carotene, Vitamin E & C)
Act as steroid hormones (Vitamin D, retinoic acid)

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4
Q

What may cause deficiency of micronutrients?

A

Inadequate intake (or general malnutrition)
Poor absorption from the intestinal tract (old age)
Inefficient utilization
Increased loss
Increased demand (pregnancy or the adolescent growth spurt)
May manifest during illness
May occur as a result of surgical procedures on GIT

Multiple deficiencies are much more common than single deficiencies and lead to specific clinical syndromes

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5
Q

What are the characteristics of fat soluble vitamins?

A

Hydrophobic compounds
Absorbed efficiently only when there is normal fat absorption
Absorbed in the small intestine

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6
Q

How are fat soluble vitamins absorbed?

A

Requires micelles formed with bile salts, which facilitate the solubilization of dietary lipids and other hydrophobic molecules

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7
Q

How are fat soluble vitamins transported in blood?

A

Blood in lipoproteins or bound to specific proteins

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8
Q

What happens to excess fat soluble vitamins?

A

Excess fat soluble vitamins are stored so toxicity can result from their excessive intake

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9
Q

What factors may lead to deficiency of fat soluble vitamins?

A

Dietary deficiency
Fat malabsorption (vitamins A, D, E and K)
Mineral oil (laxatives): Indigestible and may carry fat soluble vitamins out of the digestive system

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10
Q

What conditions may cause deficiency of vitamins A, D, E and K

A

Steatorrhea, disorders of biliary system, diseases of liver or gallbladder, inflammatory bowel disease (Crohn’s disease, celiac disease) and cystic fibrosis

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11
Q

What are the functions of fat soluble vitamins?

A

Vitamin A: Vision and cell differentiation
Vitamin D: Calcium and phosphate metabolism
Vitamin E: Antioxidants
Vitamin K: Blood clotting

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12
Q

What do deficiencies of fat-soluble vitamins cause?

A

Vitamin A deficiency: Night blindness & xerophthalmia
Vitamin D deficiency: Rickets & osteomalacia
Vitamin E deficiency: Neurologic disorders & hemolytic anemia of newborn
Vitamin K deficiency: Hemorrhage of the newborn

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13
Q

What is orlistat?

A

Drug which inhibits absorption of fat-soluble vitamins A, D, E, and K

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14
Q

What is the clinical use of orlistat?

A

Weight loss

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15
Q

What are some potential adverse effects of orlistat?

A

Abdominal pain, flatulence, bowel uregency/frequent bowel movements, steatorrhea, decreased absorption of fat-soluble vitamins

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16
Q

What is the mechanism of orlistat?

A

Inhibits fastric and pancreatic lipase which decreases teh breakdown and aborption of dietary fats

17
Q

What are the characteristics of the B group of vitamins?

A

Water soluble
Free absorption & transportation
Excesses excreted
No significant stores
Most function as coenzymes

18
Q

What are the categories into which the B group of vitamins can be subdivided?

A

Energy releasing: Thiamin, Riboflavin, Niacin, Pantothenic acid & Biotin
Hematopoietic: Folic Acid and B12
Vitamin with both & other functions: Pyridoxine

19
Q

Why does deficiency of B vitamins produce a number of overlapping symptoms?

A

Participate in many biochemical reactions
Have common food sources

20
Q

Where may deficiency symptoms arise?

A

In rapidly growing tissues

21
Q

What happens to excess water soluble vitamins?

A

Excesses of water-soluble vitamins are excreted and so unlikely to reach toxic levels.

22
Q

What are the names of the water soluble vitamins?

A
23
Q

Effects of B complex deficiencies

A

Dermatitis glossitis and diarrhea

24
Q

Do all B-complex vitamins get washed out from the body easily?

A

B12 remains in the liver for 3-4 years
B9 remains in the liver for 3-4 months

25
Q

Comparison of the properties of water soluble and fat soluble vitamins

A
26
Q

What are the characteristics of vitamin D?

A

Vitamin D is made in the skin after exposure to sunlight
Dietary source is required only when there is inadequate exposure to sunlight
Regarded as steroid hormone because of its mechanism of action

27
Q

What is the main dietary source of niacin

A

Synthesized from tryptophan is a more important dietary source of niacin than preformed niacin

28
Q

Summary of water soluble vitamin deficiencies

A
29
Q

Summary of fat soluble vitamin deficiencies

A

MD1S2: Biochemistry 202 (21 decks)

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