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MGM (D) > Lecture 53 & 54 > Flashcards

Lecture 53 & 54 Flashcards

1
Q

What are vitamins?

A

1) Vitamins are organic compounds required in the diet in small amounts
2) They are conveniently classed as fat soluble (A, D, E, & K) or water soluble (C & the B complex)

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2
Q

What is the recommended daily dietary allowance for Ascorbic Acid?

A

60 mg

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3
Q

What is the recommended daily dietary allowance for Niacin?

A

19 mg

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4
Q

What is the recommended daily dietary allowance for Vitamin E?

A

10 mg

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5
Q

What is the recommended daily dietary allowance for Pyridoxine?

A

2 mg

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6
Q

What is the recommended daily dietary allowance for Riboflavin?

A

1.7 mg

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7
Q

What is the recommended daily dietary allowance for Thiamine?

A

1.5 mg

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8
Q

What is the recommended daily dietary allowance for Vitamin A?

A

1 mg

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9
Q

What is the recommended daily dietary allowance for Folic acid?

A

400 micro g

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10
Q

What is the recommended daily dietary allowance for Vitamin K?

A

80 micro g

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11
Q

What is the recommended daily dietary allowance for Vitamin D?

A

15 micro g

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12
Q

What is the recommended daily dietary allowance for Vitamin B12?

A

3 micro g

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13
Q

What is the function of Vitamin A?

A

1) Retinol is a precursor for tinal that is used in the visual cycle and for retinoic acid that is required for maintenance of epithelial cells
2) In the visual cycle, opsin binds the 11-cis isomer of retinal. Light causes the conversion to the all-trans isomer which is only weakly bound to opsin

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14
Q

What occurs in Vitamin A deficiency?

A

1) Night blindness

2) Keratinization of epithelial cells

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15
Q

From what sources is Vitamin A obtained?

A

1) Vegetables
2) Fish liver oil
(Note: Beta-carotene is a precursor of retinol, a form of Vitamin A)

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16
Q

What is the RDA of Vitamin A?

A

1) 1000 retinol equivalents (corresponds to 1000 micro g retinol or 6000 micro g beta-carotene)
2) Excess Vitamin A is toxic

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17
Q

How is retinal formed?

A

Beta-Carotene + O2 –> 2 Retinal (Beta-Carotene dioxygenase)

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18
Q

How is retinoic acid converted to the all-trans form?

A

Retinoic acid is converted by photoisomeration

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19
Q

Where is retinol stored?

A

Retinol is stored as retinyl esters mainly in liver & adipose tissue

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20
Q

What is Rhodopsin?

A

Rhodopsin, also known as visual purple, is a biological pigment in photoreceptor cells of the retina that is responsible for the first events in the perception of light

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21
Q

Describe the cyclic process between 11-cis retinal & all trans retinal

A

11-cis retinal + Opsin –> Rhodopsin

Rhodopsin –> light + opsin + All trans retinal

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22
Q

What are actions in target tissues for retinol?

A

1) Retinol is oxidized to retinoic acid, which binds to nuclear receptors
2) Activated retinoic acid receptor stimulates responsive genes

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23
Q

What can retinol be obtained from?

A

1) Meat –> Retinol-esters –> Retinol (in lumen)
2) Retinol (in lumen) –> Retinol (in intestinal mucosal cells with help of bile acids)
3) Retinol + NAD+ –> Retinal + NADH
4) Retinal –> Retinoic acid (Oxidation)

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24
Q

Where can Beta-carotene be obtained from?

A

Vegetables –> Beta Carotene (lumen) –> Beta Carotene (intestinal mucosa with help of bile acids) + O2 –> Retinal –> Retinoic Acid

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25
Q

What is retinol?

A

1) Retinol is one of the animal forms of vitamin A
2) When converted to the retinal (retinaldehyde) form, vitamin A is essential for vision, and when converted to retinoic acid is essential for skin health, teeth remineralization and bone growth.
3) Retinol is a lipid and requires assistance in transport
4) All-trans retinoic binds to RAR receptors and 9-cis retinoic acid binds to RXR receptors

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26
Q

What is the function of thiamine (vitamin B1)?

A

Thiamine is converted to thiamine pyrophosphate which is a cofactor for oxidative decarboxylation of alpha-keto acids and for transketolase

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27
Q

What effect does a deficiency of thiamine (vitamin B1) have on the body?

A

1) Beri-beri & Wernicke-Korsakoff syndrome
2) Polyneuritis
3) Cardiac pathology
4) Edema

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28
Q

What are dietary sources of thiamine?

A

1) Beans
2) Nuts
3) Fruits

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29
Q

What is the recommended daily allowance of thiamine?

A

1.5 mg/day

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30
Q

What is the function of Riboflavin (vitamin B2)?

A

Riboflavin is a precursor for the coenzymes, FMN & FAD

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31
Q

What effect does a deficiency of riboflavin (vitamin B2) have on the body?

A

Skin lesions

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32
Q

What are dietary sources of riboflavin?

A

1) Milk
2) Liver
3) Green vegetables

33
Q

What is the recommended daily allowance of riboflavin?

A

1.7 mg/day

34
Q

Describe the formation of flavin mononucleotide (FMN) & Flavin adenine dinucleotide (FAD) from riboflavin

A

1) Riboflavin + ATP –> Flavin mononucleotide (FMN) + ADP

2) Flavin mononucleotide (FMN) + ATP –> PPi + Flavin adenine dinucleotide

35
Q

What is the function of niacin (nicotinic acid)?

A

Nicotinic acid or nicotinamide are precursors for the coenzymes NAD & NADP

36
Q

What effect does a deficiency of niacin have on the body?

A

Pellagra (dermatitis, diarrhea, dementia, and if severe, death)

37
Q

What are two sources of niacin?

A

1) Legumes

2) Meat

38
Q

What is the recommended daily allowance of niacin?

A

19 mg/day

39
Q

What is the function of pantothenic acid?

A

Pantothenic acid is a precursor of pantotheine. This structure forms part of coenzyme A

40
Q

What effect does a deficiency of pantothenic acid have on the body?

A

A deficiency is practically unknown. There may be nausea and fatigue

41
Q

What are dietary sources of pantothenic acid?

A

Pantothenic acid is widely distributed and is synthesized by some intestinal bacteria

42
Q

What is the recommended daily allowance of pantothenic acid?

A

An RDA has not been established, but 5-10 mg/day might be used

43
Q

What is the function of pyridoxine (Vitamin B6)?

A

Pyridoxine (pyridoxol) is a precursor of pyridoxal phosphate (PLP) which is a coenzyme for enzymes catalyzing transamination, deamination, decarboxylation and for glycogen phosphorylase

44
Q

What effect does a deficiency of pyridoxine (vitamin B6) have on the body?

A

1) Dermatitis
2) Convulsions
3) Microcytic anemia

45
Q

What are dietary sources of pyridoxine?

A

1) Liver
2) Fish
3) Nuts
4) Whole grain cereals

46
Q

What is the recommended daily allowance of pyridoxine?

A

2 mg/day

47
Q

What is the function of biotin?

A

Biotin acts as a coenzyme in carboylation reactions in covalent linkage to lysine side chains of enzymes

48
Q

What effect does a deficiency of biotin have on the body?

A

1) Dermatitis
2) Anorexia
3) Nausea
4) Muscle pain

49
Q

What are dietary sources of biotin?

A

1) Intestinal microorganisms
2) Liver
3) Vegetables

50
Q

What is the recommended daily allowance of biotin?

A

An RDA has not been established. Not avidin in raw eggs has tight binding for biotin and in high amounts can cause a biotin deficiency

51
Q

What is the function of folic acid?

A

Folic acid is a precursor for tetrahyhdrofolate that is used as a carrier of one carbon units at different levels of oxidation

52
Q

What effect does a deficiency of folic acid have on the body?

A

1) Megaloblastic anemia

2) GI disturbances

53
Q

What are dietary sources of folic acid?

A

1) Intestinal bacteria
2) Liver
3) Yeast
4) Green vegetables

54
Q

What is the recommended daily allowance of folic acid?

A

400 micrograms/day

Note: Before supplementation, folic acid deficiency was the most common vitamin deficiency in the US

55
Q

What is the function of sulfanilamide?

A

Sulfanilamide and its derivatives competitively inhibit the synthesis of folic acid in micro organisms and, thereby, decrease the synthesis of nucleotides needed for the replication

56
Q

What is the function of methotrexate?

A

1) Dihydrofolate reductase is competitively inhibited by methotrexate, a folic acid analogue used to effect the remission of acute leukemia in children
2) Dihydrofolate reductase normally reduces folic acid to tetrahydrofolic acid by oxidizing NADPH to NADP+
3) Tetrahydrofolic acid can then be used for Amino acid synthesis, purine synthesis, & thymidine synthesis

57
Q

What is the structure vitamin B12 (Cobalamin) entail?

A

Vitamin B12 is a complex multiple ring structure which includes a cobalt atom

58
Q

What is the function of Vitamin B12 (cobalamin)?

A

Derived cofactors are used for two important reactions:

1) Methylmalonyl CoA isomerase requires 5-deoxyadenosyl cobalamin
2) Homocysteine: Tetrahydrofolate methyl transferase requires methyl cobalamin

59
Q

How is Vitamin 12 absorbed by the body?

A

Vitamin B12 is absorbed from the ileum as a complex with intrinsic factor which is produced by the gastric mucosa

60
Q

What effect does a deficiency in Vitamin B12 have on the body?

A

1) Pernicious anemia

2) Degeneration of spinal cord neurons

61
Q

What are dietary sources of Vitamin B12?

A

1) Meat

2) Milk

62
Q

What is the RDA for Vitamin B12?

A

3 micrograms/day

63
Q

What is the function of Vitamin C (Ascorbic acid)?

A

1) Ascorbic acid is a water soluble antioxidant and it promotes the hydroxylation of proline residues of collagen
2) Ascorbic acid is also required in the synthesis of carnitine, dopamine and bile acids

64
Q

What effect does a deficiency of vitamin C have on the body?

A

Scurvy (hemorrhage, impaired wound healing, and bond formation)

65
Q

What are dietary sources of vitamin C?

A

1) Fruits

2) Vegetables

66
Q

What is the RDA for vitamin C?

A

60 mg/day

67
Q

What is the function of vitamin D?

A

1) Regulation of calcium levels through actions on intestine, kidney & bone
2) Vitamin D3 (cholecalciferol) requires conversion to 1,25-dihydroxy vitamin D3 to form the active compound

68
Q

What effect does a deficiency of vitamin D have on the body?

A

1) Rickets

2) Osteomalacia

69
Q

What are dietary sources of Vitamin D?

A

1) UV irradiation of 7-dehydrocholesterol in the skin
2) fish liver oils
3) supplemented milk

70
Q

What is the RDA for vitamin D?

A

600 international units (15 micrograms of cholecalciferol)

71
Q

What is the function of Vitamin E (Tocopherol)?

A

It is a lipid-soluble antioxidant and helps to prevent lipid damage

72
Q

What effect does a deficiency of vitamin E have on the body?

A

In humans, deficiency is associated with lysis of erythrocytes

73
Q

What are dietary sources of Vitamin E?

A

1) Vegetables

2) Wheat germ oil

74
Q

What is the RDA for Vitamin E?

A

15 international units. Greater amounts may be beneficial but there is conflicting data

75
Q

What is the function of Vitamin K?

A

It is a coenzyme for the carboxylation of glutamic acid side chains of some blood clotting factors (prothrombin, factors 7, 9, & 10)

76
Q

What effect does a deficiency in vitamin K have on the body?

A

A deficiency of vitamin K is rare, but can be associated with prolonged blood clotting times

77
Q

What are dietary sources of Vitamin K?

A

Vitamin K is produced by intestinal bacteria

78
Q

What is the RDA for vitamin K?

A

No RDA has been established, but 70-140 micrograms may be appropriate

79
Q

What is a consequence of folic acid deficiency?

A

Spina bifida

MGM (D) (71 decks)

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