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x M1 Biochem Term 2 Quiz 4 > Vitamins > Flashcards

Vitamins Flashcards

(53 cards)

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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

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A

Component of coenzyme A (transfers acyl groups).

23
Q

Vitamin B5 (Pantothenic Acid): Clinical Sig

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A

As yet uncharacterized. B5 not critical for life.

24
Q

Vitamin B6 (Pyrodoxine): Biochem Fxn

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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
Vitamin B6 (Pyrodoxine): Clinical Sig
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
Vitamin B7 (Biotin): Biochem Fxn
Coenzyme in carboxylation reactions. Covalently bound to to lysine groups of specific enzymes. Anomalous in that it becomes part of enzyme.
27
Vitamin B7 (Biotin): Clinical Sig
Deficiency --> mild depression. Caused by eating >20 raw eggs per day.
28
Vitamin B9 (Folate): Biochem Fxn
Necessary for one-carbon metabolism, incl purine and thymidine synthesis (therefore DNA synthesis). PABA --> folate --> THF --> DNA synthesis.
29
Vitamin B9 (Folate): Clinical Sig
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
Methotrexate blocks what process?
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
Vitamin B12 (Cobalamin): Biochem Fxn
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
Vitamin B12 (Cobalamin): Clinical Sig
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
Vitamin B12 (Cobalamin): Treatment
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
Explain the folate trap hypothesis
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
B12 requires what for intestinal absorption?
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
Vitamin C: Biochem Fxn
Required for hydroxylation of lysine and proline residues in collagen, promoting cross-linkage. Also antioxidant.
37
Vitamin C: Clinical Sig
Deficiency causes scurvy. Connective tissue breakdown: hair follicles, gums, hemorrhages, poor wound healing. Excess Vit C can cause oxalic acid kidney stones.
38
Qualtities of fat-soluble vitamins:
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
Vitamin A: Biochem Fxn
Collective term for 4 molecules (retino….). Required for reproduction, differentiation of epithelial cells, visual pigment of rhodopsin.
40
Vitamin A: Clinical Sig
Deficiency leads to blindness. First Sx = night blindness. Other signs of deficiency: Bitot's spots, corneal epithelial cell keratinization.
41
Vitamin A: Treatment
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
Hypervitaminosis A causes…?
dry skin, liver damage, raised intracranial pressure
43
Vitamin D: Biochem Fxn
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
Vitamin D: Clinical Sig
Adults: deficiency --> osteomalacia (softening of bones). Also, demineralization, bone pain, microfractures. Children: Rickets (failure to mineralize developing leg bones, bend due to pressure).
45
Vitamin D: Therapy
Give calcitriol, but watch for hypercalcaemia (bones, stones, abdominal moans)
46
Vitamin E: Biochem Fxn
Antioxidant, protects lipid membranes.
47
Vitamin E: Clinical Sig
Deficiency can cause RBC fragility.
48
Vitamin K: Biochem Fxn
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
Vitamin K: Source
Intestinal bacteria. Therefore frequently administered to neonates who still haven't developed gut flora.
50
Vitamin K: Clinical Sig
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
Most common vitamin deficiency in US?
Folate, esp in preg women and EtOH abusers.
52
What water-soluble vitamin is not found in plants?
B12
53
What water-soluble vitamin has body stores of up to several years?
B12

x M1 Biochem Term 2 Quiz 4 (4 decks)

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