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x M1 Biochem Term 2 Quiz 4 > Vitamins > Flashcards

Vitamins Flashcards

2
Q

Vitamin B1

A

Thiamine; water soluble.

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3
Q

Vitamin B2

A

Riboflavin; water soluble.

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4
Q

Vitamin B3

A

Niacin; water soluble.

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5
Q

Vitamin B5

A

Pantothenic Acid; water soluble.

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6
Q

Vitamin B6

A

Pyrodoxine; water soluble

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7
Q

Vitamin B7

A

Biotin; water soluble.

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8
Q

Vitamin B9

A

Folate; water soluble; hematopoietic

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9
Q

Vitamin B12

A

Cobalamin; water soluble; hematopoietic

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10
Q

Vitamin C

A

Ascorbic Acid; water soluble

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11
Q

Vitamin A

A

Fat soluble

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12
Q

Vitamin D

A

Fat soluble

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13
Q

Vitamin E

A

Tocopherol; fat soluble

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14
Q

Vitamin K

A

Fat soluble

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15
Q

Qualities of water soluble vitamins?

A

Easily excreted in urine; low body stores; involved in intermediary metabolism as cofactors; found in plants

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16
Q

Vitamin B1 (Thiamine): Biochem Fxn

A

Cofactor for carbohydrate-metabolizing enzymes (pyrovate dehydrogenase, alpha-ketoglutarate dehydrogenase, transketolase)

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17
Q

Vitamin B1 (Thiamine): Clinical Sig

A

Two distinct deficiency disorders: Wernicke-Korsakoff and Beriberi. W-K: neuronal loss, high mortality, seen in EtOH abuse. Beriberi: dilated cardiomyopathy, peripheral neuropathy, seen in malnutrition.

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18
Q

Vitamin B1 (Thiamine): Impt Clinical Point

A

If giving IV glucose to EtOH abuser, give WITH THIAMINE.

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19
Q

Vitamin B2 (Riboflavin): Biochem Fxn

A

Riboflavin –> FMN and FAD (coenzymes). Cofactors for flavoenzymes that catalyze redox reactions.

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20
Q

Vitamin B2 (Riboflavin): Clinical Sig

A

Deficiency causes fissures at corner of mouth (cheliosis), dermatitis, and purple tongue. Not life-threatening.

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21
Q

Vitamin B3 (Niacin): Biochem Fxn

A

Nicotinamide and nicotinic acid. Both precursors for NAD and NADP coenzymes (redox reactions). Note: not technically a vitamin because can be synthesized from tryptophan. (Possible to be deficient since pathway from tryptophan –> niacin is inefficient, and some disease states prevent the pathway.)

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22
Q

Vitamin B3 (Niacin): Clinical Sig

A

4 Ds: dermatitis, diarrhea, dementia, death. Pretty fucking miserable. Pellagra (sour skin) - photosensitive rash. Deficiency seen in some pts with Hartnup disease (diminished tryptophan update) and carcinoid syndrome (due to altered tryptophan metabolism)

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23
Q

Vitamin B5 (Pantothenic Acid): Biochem Fxn

A

Component of coenzyme A (transfers acyl groups).

23
Q

Vitamin B5 (Pantothenic Acid): Clinical Sig

A

As yet uncharacterized. B5 not critical for life.

24
Q

Vitamin B6 (Pyrodoxine): Biochem Fxn

A

Collective term for 3 enzymes (pyridox…..). All are precursors for pyridoxal phosphate, a coenzyme in reactions involving metabolism of AAs (transamination, deamination, decarboxylation, condensation).

25
Q

Vitamin B6 (Pyrodoxine): Clinical Sig

A

Deficiency manifests as seizures, unknown why. When isoniazid (given for latent TB, B6 antagonist) is Rx’d, often also give B6 to prevent B6 functional deficiency.

26
Q

Vitamin B7 (Biotin): Biochem Fxn

A

Coenzyme in carboxylation reactions. Covalently bound to to lysine groups of specific enzymes. Anomalous in that it becomes part of enzyme.

27
Q

Vitamin B7 (Biotin): Clinical Sig

A

Deficiency –> mild depression. Caused by eating >20 raw eggs per day.

28
Q

Vitamin B9 (Folate): Biochem Fxn

A

Necessary for one-carbon metabolism, incl purine and thymidine synthesis (therefore DNA synthesis). PABA –> folate –> THF –> DNA synthesis.

29
Q

Vitamin B9 (Folate): Clinical Sig

A

Essential for cell division, esp in fetuses and blood cells. In fetuses, deficiency –> neural tube defects. In adults, deficiency –> megaloblastic anemia (see in blood smear).

30
Q

Methotrexate blocks what process?

A

Blocks folate conversion to THF, which is required for DNA synthesis. Methotrexate given as a cancer drug. Can lead to megaloblastic anemia despite sufficient dietary folate. (Tx = give THF in form of drug: leukovorin)

31
Q

Vitamin B12 (Cobalamin): Biochem Fxn

A

Very similar structure to heme/porphyrin. Central ion = cobalt. Precursor to 2 essential coenzymes: methylcobalamin (blood cells: needed to synthesize methionine from homocysteine) and deoxyadenosylcobalamin (needed for FA metabolism in brain cells). In both cases, needed for rapidly dividing cells.

32
Q

Vitamin B12 (Cobalamin): Clinical Sig

A

Deficiency causes megaloblastic anemia due to functionally trapping folate. Also, subacute combined degeneration of spinal cord and dementia.
Deficiency can look like folate deficiency.

33
Q

Vitamin B12 (Cobalamin): Treatment

A

Tx with folate will solve the anemia but will not solve the CNS problems; may actually mask the CNS problems. Degeneration of spinal cord initially indicated by loss of vibration sense on feet.

34
Q

Explain the folate trap hypothesis

A

During methionine synthesis: N5-methyl-THF transfers a methyl group to B12 –> methylcobalamin. Same reaction needed to metabolize N5-methyl-THF. If no B12, N5-methyl-THF cannot be used for DNA synthesis (ie, folate is trapped on N5-methyl-THF).

35
Q

B12 requires what for intestinal absorption?

A

Intrinsic factor (IF) created by parietal cells. In pernicious anemia (AI disorder, destroys parietal cells), IF is absent –> B12 deficiency. Treat with IM B12 to circumvent need for IF.

36
Q

Vitamin C: Biochem Fxn

A

Required for hydroxylation of lysine and proline residues in collagen, promoting cross-linkage. Also antioxidant.

37
Q

Vitamin C: Clinical Sig

A

Deficiency causes scurvy. Connective tissue breakdown: hair follicles, gums, hemorrhages, poor wound healing. Excess Vit C can cause oxalic acid kidney stones.

38
Q

Qualtities of fat-soluble vitamins:

A

Stored in adipose tissue; stores in body can last for several months. Possible to ingest toxic doses (esp A and D) due to accumulation in fat over time. Deficiencies often seen in pts with fat malabsorption syndromes.

39
Q

Vitamin A: Biochem Fxn

A

Collective term for 4 molecules (retino….). Required for reproduction, differentiation of epithelial cells, visual pigment of rhodopsin.

40
Q

Vitamin A: Clinical Sig

A

Deficiency leads to blindness. First Sx = night blindness. Other signs of deficiency: Bitot’s spots, corneal epithelial cell keratinization.

41
Q

Vitamin A: Treatment

A

Night blindness can be treated with Vit A therapy. Retinoic Acid = treatment for acne, psoriasis. Vit A is teratogenic: do not give to preg women!

42
Q

Hypervitaminosis A causes…?

A

dry skin, liver damage, raised intracranial pressure

43
Q

Vitamin D: Biochem Fxn

A

D2 found in plants (and converted to D3 in body), D3 in animals. D3 converted to calcitriol in body. Calcitriol (steroid hormone) increases Ca2+ absorption in intestine and decreases calcium excr in kidney –> higher plasma Ca2+ levels. Can be made endogenously by exposure to UV light.

44
Q

Vitamin D: Clinical Sig

A

Adults: deficiency –> osteomalacia (softening of bones). Also, demineralization, bone pain, microfractures. Children: Rickets (failure to mineralize developing leg bones, bend due to pressure).

45
Q

Vitamin D: Therapy

A

Give calcitriol, but watch for hypercalcaemia (bones, stones, abdominal moans)

46
Q

Vitamin E: Biochem Fxn

A

Antioxidant, protects lipid membranes.

47
Q

Vitamin E: Clinical Sig

A

Deficiency can cause RBC fragility.

48
Q

Vitamin K: Biochem Fxn

A

Involved in one reaction: post-translational carboxylation of glutamate, which is required for Ca2+ binding by blood clotting factors (incl prothrombin). Addition of second neg charge allows binding to Ca2+ at cell membrane. Basically, impt in clotting cascade.

49
Q

Vitamin K: Source

A

Intestinal bacteria. Therefore frequently administered to neonates who still haven’t developed gut flora.

50
Q

Vitamin K: Clinical Sig

A

Deficiency leads to hemorrhage with long prothrombin time (measure of clotting tendency of blood: long PT = less clotting). Vit K action opposes coumadin/warfarin (anti-coagulants). Ie, Vit K deficiency mimics anticoagulant effect.

51
Q

Most common vitamin deficiency in US?

A

Folate, esp in preg women and EtOH abusers.

52
Q

What water-soluble vitamin is not found in plants?

A

B12

53
Q

What water-soluble vitamin has body stores of up to several years?

A

B12

x M1 Biochem Term 2 Quiz 4 (4 decks)

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