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Biochem Exam 4 > Vitamins > Flashcards

Vitamins Flashcards

1
Q

What are vitamins?

A

Chemically unrelated organic compounds that we cannot synthesize in adequate quantities

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2
Q

What are the vitamins that toxicity is rare, deficiencies can occur quickly and many are coenzyme precursors?

A

9 water-soluble

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3
Q

What are the vitamins that can lead to accumulation of toxic quantities?

A

4 fat-soluble

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4
Q

What are the water soluble vitamins?

A

Ascorbic acid (C) and B complex

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5
Q

What are the fat soluble vitamins?

A 
A (retinol, beta-carotenes)
D (cholecalciferol)
K (phylloquinones, menaquinones)
E (tocopherols)
-must know all names
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6
Q

What are the energy releasing B complex vitamins?

A 
Thiamine (B1)
Riboflavin (B2)
Niacin (B3)
Pantothenic acid (B5)
Biotin (B7)
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7
Q

What are the hematopoietic B complex vitamins?

A 
Folic acid (B9)
Cobalamin (B12)
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8
Q

What are the B6 vitamins?

A

Pyridoxine
Pyridoxal
Pyridoxamine

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9
Q

What is the most common deficiency in US, especially pregnant women/alcoholics?

A

Folic acid (B9)

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10
Q

What is folic acid used to make?

A

Tetrahydrofolate (transfers 1-C groups)

-Synthesis of methionine, purine and thymidine monophosphate

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11
Q

What are nutritional anemias?

A

Lower than normal [Hb] -> reduced ability to transport oxygen

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12
Q

What is microcytic anemia?

A

Size of RBC < normal

  • Caused by lack of iron
  • Most common
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13
Q

What is macrocytic anemia?

A

Size of RBC > normal

-Deficiency in folic acid/B12

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14
Q

Where is cobalamin (B12) found?

A

Liver, red meat, fish, eggs, dairy, fortified cereals

-Not in plants

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15
Q

What does a deficiency in B12 cause?

A

Megaloblastic anemia

  • Can’t make sugar from fat
  • Can’t make methionine
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16
Q

What is special about B12?

A

Corrin ring w/ cobalt at the center

-Looks like heme

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17
Q

What does malabsorption of B12 lead to?

A

Pernicious anemia

-R-protein + intrinsic factor needed for proper absorption

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18
Q

What does vitamin C fx as?

A

Reducing agent

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19
Q

What is vitamin C a coenzyme in?

A

Hydroxylation rxn of prolyl and lysyl residues of collagen

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20
Q

What are key dietary antioxidants?

A

Vitamin C + E + beta-carotene

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21
Q

What does vitamin C deficiency cause?

A

Scurvy

-Deficiency in hydroxylation of collagen -> defective CT

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22
Q

All vitamin B6s are derivatives of what?

A

Pyridine

23
Q

What is an important role of B6?

A

Pyridoxal phosphate (PLP): active coenzyme in rxns involving AAs

24
Q

What does >500 mg/day intake of B6 cause?

A

Neurologic sx

25
Q

What is the biologically active form of B1?

A

Thiamine pyrophosphate (TPP) -> energy

  • Role in PPP
  • Role in pyruvate -> acetyl CoA (by pyruvate dehydrogenase)
  • Role in alpha-ketoglutarate -> succinyl CoA (by alpha-ketoglutarate dehydrogenase)
26
Q

What does a B1 deficiency cause?

A

Decreased production of ATP

27
Q

What is beriberi?

A

B1 deficiency; in areas where polished rice is major component of diet

28
Q

What is wernicke-korsakoff syndrome?

A

B1 impaired absorption; chronic alcoholism

29
Q

What are the biologically active coenzyme forms of Niacin (B3)?

A

Nicotinamide adenine dinucleotide (NAD+) and NADP+

  • necessary for ETC, accepts a hydride ion
  • found in unrefined/enriched grains/cereal, milk, lean meats/liver
30
Q

What does B3 deficiency cause?

A

Pellagra -> 3Ds: dermatitis, diarrhea, dementia

31
Q

What is B3 useful in treatment of?

A

Hyperlipoproteinemia

32
Q

What are the biologically active forms of riboflavin (B2)?

A

FMN and FAD

  • Reversibly accepts 2 H atoms
  • Bound tightly to flavoenzymes
33
Q

What is Biotin (B7) a coenzyme in?

A

Carboxylation rxns (carrier of activated CO2)

34
Q

What is biotin covalently bound to?

A

Amino group of lysine residues in biotin-dependent enzymes

-Weird because coenzymes are not usually covalently linked

35
Q

Where is biotin?

A

Widely distributed in food

  • Very rare you see a deficiency
  • Large % supplied by intestinal bacteria
36
Q

What is pantothenic acid (B5) component of?

A

CoA

-Sulfhydryl group (always makes a thiol ester)

37
Q

Where is B5 found in?

A

Eggs, liver, yeast

38
Q

What is vitamin A (retinoids) related to?

A

Dietary retinol

39
Q

What is vit A essential for?

A

Vision, reproduction, growth and maintenance of epithelial tissues

40
Q

What are vit A sources?

A

Pre-formed: liver, kidney, cream, butter, egg yolk

Precursors: carotenes (yellow, orange, dark green veggies)

41
Q

What does vitamin A dietary deficiency cause?

A
  • Night blindness (early sign)

- Prolonged defic -> irreversible loss in # visual cells

42
Q

How many children worldwide are blinded due to vit A defic?

A

> 500,000

43
Q

What are vit A actions as therapeutic agents?

A

Tx of skin aging/mild-severe acne/psoriasis, tx of acute promyelocytic leukemia

44
Q

What are vit A actions as dietary components?

A

Maintenance of reproduction/vision, promotion of growth, differentiation/maintenance of epithelial tissue; gene expression

45
Q

What is vitamin D?

A

Group of sterols that have hormone-like fx

46
Q

What is the active molecule of vitamin d?

A

1,25-dihydroxycholecalciferol (calcitriol)

-Binds intracellular receptors

47
Q

What does vit D regulate the plasma levels of?

A

Calcium + phosphorous

48
Q

What does deficiency of vitamin D cause?

A

Demineralization of bone -> rickets (children) ; osteomalacia (adults)

49
Q

What do high doses of vit D cause?

A

Loss of appetite, nausea, thirst, stuppor

-> deposition of Ca2+ in arteries/kidneys

50
Q

What is vitamin K a coenzyme in?

A

Gamma-carboxylation of certain glutamic acid residues

-Necessary for blood clotting

51
Q

Where is vitamin K found?

A

Cabbage, kale, spinach, egg yolk, liver, synthesis by bacteria in gut

52
Q

What does vitamin E do?

A

Main role in antioxidant

53
Q

What is the most active form of E?

A

alpha-tocopherol

54
Q

Why is vitamin E important to get in your diet?

A

Least toxic of fat-soluble vitamins

Biochem Exam 4 (7 decks)

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