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biochem term 2 quiz 4 > vitamins > Flashcards

vitamins Flashcards

1. learn the biochemical function of each vitamin 2. learn the clinical significance of each vitamin

1
Q

what does recommended daily allowance (RDA) reflect?

A

they do not reflect the nutritional needs of individuals but rather provide a tool to compare the contribution of specific food items to the overall diet - what each person needs is an individual things - can actually convert to mg - so really just a unit of measure - approximation of what the average person may need

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2
Q

in what kinds of patients do vitamin deficiencies normally occur?

A

alcohol abusers, elderly patients, patients with small bowel resections, food faddists, and malnourished people in the developing world

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3
Q

where can we get water-soluble vitamins in our diets?

A

all water soluble vitamins except for B12 are in vegetables

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4
Q

water-soluble vitamins (summary)

A

1: most are precursors of coenzymes involved in intermediary metabolism
2: all water soluble vitamins except for vitamin B12 are present in vegetables
3: deficiency of all water soluble vitamins except for vitamin b12 produces clinical symptoms within weeks due to low body stores

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5
Q

what are most water-soluble vitamins precursors to?

A

most are precursors of coenzymes involved in intermediary metabolism

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6
Q

how long does it take for symptoms of vitamin deficiency to occur?

A

deficiency of all water-soluble vitamins except for B12 produces clinical symptoms within weeks due to low body stores

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7
Q

vitamin B1 (summary)

A

thiamine pyrophosphate is a coenzyme for enzymes involved in carbohydrate metabolism, specifically pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase
deficienys causes korsakoff’s in alcohol abusers

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8
Q

what enzymes is thiamine pyrophosphate (vitamin B1) a coenzyme for?

A

enzymes involve in carbohydrate metabolism

  • pyruvate dehydrogenase
  • alpha-ketoglutarate dehydrogenase
  • transketolase
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9
Q

what is the result of vitamin B1 deficiency?

A

beriberi-peripheral neuropathy and dilated cardiomyopathy
deficiency results in korsakoff’s syndrome in alcohol abusers
administer thiamine with glucose to alcohol abusers
would see impaired eye movements (mystagmus) and ataxia

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10
Q

what patient population would you expect to see korsakoff’s syndrome in?
what should be administered with thiamine to these patients?

A

alcohol abusers

administer thiamine with glucose to alcohol abusers

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11
Q

what is vitamin B2 (riboflavin) a precursor for?

A

flavin mononucleotide (FMN) and flavin dinucleotide (FAD) coenzymes

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12
Q

what is the result of riboflavin/vitamin B2 deficiency?

A

fissuring at the angles of the mouth
dermatitis
purple tounge

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13
Q

what two compounds can vitamin B3/niacin be found as?

A

nicotinamide or nicotinic acid

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14
Q

what enzymes is vitamin B3/niacin a precursor for?

A

nicotinaminde adenine dinucleotide (NAD)

nicotinamide adenine dinucleotide phosphate (NADP)

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15
Q

why isn’t vitamin B3/niacin technically a vitamin?

A

because humans can synthesize niacin from tryptophan

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16
Q

what does vitamin B3/niacin deficiency cause?

A

pellagra (italian for sour skin)

dermatitis, diarrhea, dementia and death

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17
Q

in what types of patients would you expect to see vitamin B3/niacin deficiency?

A

patients with Hartnup disease (diminshed tryptophan uptake)

patients with carcinoid syndrome (altered tryptophan metabolism)

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18
Q

what can vitamin B3/niacin be used for theraputically? in what disorder is this treatment used?

A

used to lower LDL and VLDL cholesterol in type IIb hyperlipoproteinemia

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19
Q

what coenzyme is vitamin B5/pantothenic acid a component of?

A

coenzyme A

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20
Q

what is the result of vitamin B5/pantothenic acid deficiency?

A

none yet discovered - it’s widely available in food and so deficiency syndrome has not been characterized

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21
Q

what three molecules does vitamin B6 collectively describe?

A

pyridoxine, pyridoxal and pyridoxamine

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22
Q

what coenzyme is vitamin B6 a precursor for and what does it do?

A

precursors of pyridoxal phosphate, which catalyzes reactions involving amino acids

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23
Q

what drug does vitamin B6 bind to and what is done about this?

A

it binds to the antituberculosis drug isoniazid

as a result, B6 is routinely perscribed with anti-TB drugs to prevent a deficiency in B6

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24
Q

what does a deficiency in vitamin B6 cause?

A

seizures

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25
what is vitamin B7/biotin a coenzyme for?
in carboxylation reactions | in these, it's covalently bound to specific lysine residues of biotin-containing enzymes
26
what is the result of a vitamin B7/biotin deficiency?
dermatitis glossitis nausea
27
how would someone acquire a biotin/vitamin B7 deficiency?
by eating greater than 20 raw eggs per day raw eggs contain a biotin-binding protein called avidin - in the egg whites apparently people use egg whites as supplements, so could see this in body builders, etc.
28
what molecules is vitamin B9/folate necessary for?
for one-carbon metabolism, including the synthesis of purine and thymidine (and therefore DNA)
29
what does vitamin B9/folate deficiency cause? how would these deficiencies be acquired?
in adults: megaloblastic anemia, patients taking chemo drugs (methotrexate) - causes shortness of breath due to anemia pregnant women because fetus is using so much folate alcohol abusers in fetuses: neural tube defects -mother didn't get enough folate during first trimester - part of brain or spinal cord can become externalized (spina bifida, anencephaly)
30
how is folate deficiency prevented in our diets?
it has been supplemented in "enriched" foods since 1998 - for people who are alcohol abusers
31
what is vitamin B12/cobalamin a precursor for? | what products is that used to synthesize?
precursor for methylcoalamin needed to synthesize methionine from homocysteine in blood cells also precursor for deoxyadenosylcobalamin, which is needed for fA metabolism in brain cells
32
what is required for intestinal absorption of vitamin B12/cobalamin?
``` intrinsic factor (as a result, deficiency is seen in patients with pernicious anemia, meaning they lack intrinsic factor) ```
33
in what organism is vitamin B12/cobalamin not produced?
plants
34
in what patients would you expect to see a deficiency in vitamin B12/cobalamin?
in vegans | in patients with pernicious anemia (lacking intrinsic factor)
35
what is the result of deficiency in vitamin B12/cobalamin?
megaloblastic anemia by functionally trapping folate subacute combined degeneration of the spinal cord dementia
36
why does vitamin B12/cobalamin deficiency cause megaloblastic anemia?
this is the folate trap hypothesis: during methionine synthesis, N5-methyl-THF transfers a methyl group to vitamin B12 = methylcobalamin reaction also required to metabolize N5-methyl-THF lack of B12 blocks metabolism of N5-methyl THF so it can't be used to make DNA
37
how long does it take for the clinical symptoms of vitamin B12/cobalamin deficiency to manifest?
years because there are large body stores of the vitamin
38
how is pernicious anemia treated?
with intramuscular B12 injections - circumvents the need for intrinsic factor (couldn't give B12 orally because the problem is that it's not being absorbed by parietal cells properly, so that wouldn't help)
39
which clinical manifestations of folate/vitamin B12 deficiency can be treated with folate supplementation and which cannot?
pernicious anemia with intermuscular B12 injections megaloblastic anemia due to deficiencies of vitamin B12 or folate can be ameliorated by supplementation the subacute combined degeneration of the spinal cord can't be treated by supplementation
40
what is vitamin C/ascorbic acid necessary for?
post-translational hydroxylation of proline, especially in collagen required for hydroxylation of lysine and proline residues in collagen, promoting cross-links note: only required in primates and guinea pigs
41
what does vitamin C/ascorbic acid deficiency result in?
scurvy: bleeding gums, hemorrhages around corkscrew hair follicles, bone pain caused by bleeding underneath periosteum, poor wound healing - connective tissue breakdown
42
what can overdose of vitamin C/ascorbic acid cause?
oxalic acid kidney stones
43
which vitamins are water soluble?
``` the B vitamins - 1: thiamine - 2: riboflavin - 3: niacin - 5: pantothenic acid - 6: (just itself) - 7: biotin - 9: folate - 12: cobalamin Vitamin C: ascorbic acid ```
44
which vitamins are fat soluble?
vitamins A, D, E, and K
45
fat soluble vitamins (summary)
in the US, deficiencies of fat-soluble vitamins are often present in patients with fat malabsorption syndromes fat-soluble vitamins are stored in the body and metabolized slowly - therefore deficiency usually develops only after months of inadequate intake excess consumption of either vitamin A or D leads to toxicity
46
in what type of patients would you expect to see deficiencies in fat-soluble vitamins in the US?
in patients with fat malabsorption syndromes
47
how long does it take for symptoms of a deficiency of a fat-soluble vitamin to appear?
months, since fat-soluble vitamins are stored in the body and metabolized slowly
48
which fat-soluble vitamins can cause toxicity if consumed in excess?
vitamins A or D
49
what three molecules are categorized as vitamin A?
retinol, retinal, and retinoic acid
50
what is retinal essential for?
vision - it's the pigment in rods and cones that senses light
51
what is retinoic acid essential for?
to maintain differentiation of epithelial cells
52
how is vitamin A obtained?
from animal sources or derived from beta-carotene in plants
53
what is the result of vitamin A deficiency? | what is the first symptom and how can it be improved?
deficiency causes 1.2 million cases of permanent blindness each year in the developing world the first symptom is night blindness - this can be rapidly improved with emergency vitamin A therapy
54
what are the physical signs of vitamin A deficiency? | what causes these?
xeropthalmia and Bitot's spots | caused by corneal epithelial cells dedifferentiation/keratinization
55
what is vitamin A used to treat?
acne | psoriasis
56
what occurs when too much vitamin A is consumed?
called hypervitaminosis A | results in skin rash, liver damage, raised intracranial pressure
57
what patients should you avoid giving vitamin A to and why?
vitamin A is teratogenic and so should not be given to pregnant patients
58
how is vitamin D produced?
endogenously in the skin by uv irradiation | obtained from animal (D3) or plant (D2) tissues
59
how is vitamin D converted to its active form? | where does this conversion occur?
it's active form is calcitriol requires two successive hydroxylation reactions the first is in the liver the second is in the kidney, bone or placenta
60
what does calcitriol do in the body?
it's a steroid hormone that increases calcium absorption by the intestine epithelium
61
how is vitamin D deficiency prevented in our diets?
in the US, milk is fortified with it
62
what does vitamin D deficiency result in?
in adults: demineralization of formed bone, leading to osteomalacia (bone pain, microfractures, compression fractures) in children: failure to mineralize developing bones, leading to rickets (bowed legs)
63
what are the risk factors for vitamin D deficiency?
lack of milk consumption (often due to lactose intolerance) dark skin color low sun exposure
64
what can theraputic calcitriol treatment cause?
hypercalcaemia: causes "bones, stones, and abdominal moans"
65
what is vitamin E/tocopherol important for?
it's an antioxidant that protects lipid membranes
66
what can vitamin E/tocopherol deficiency cause?
red blood cell fragility in infants
67
what biochemical reaction is vitamin K needed for? | what is this reaction needed for?
post translational carboxylation of glutamate this is required for calcium binding by several blood clotting factors, including prothrombin adds carboxyl group to several clotting factors - gives them a second negative charge - allows it to bind to Ca2+ which brings the clotting factor to the center of the cell
68
where does vitamin K come from?
it's produced by intestinal bacteria
69
what is the result of a vitamin K deficiency?
hemorrhage with a long prothromin time (PT)
70
to what patients is vitamin K clinically adminstered and why?
to premature infants who lack the intestinal bacteria to provide vitamin K to adults on long-term antibiotic therapy
71
how is vitamin K blocked and why?
it can be blocked by the drug coumadin, which is a vitamin K antagonist it prevents clotting, for example in patients with prosthetic heart valves
72
vitamin classifications (list)
``` water soluble - non-b-complex ascorbic acid - b-complex - energy-releasing thiamine (B1) riboflavin (B2) niacin (B3) biotin pantothenic acid - hematopoietic folic acid vitamin B12 - other pyridoxine (B6) pyridoxal pyridoxamine fat-soluble vitamin A (retinol; beta-carotenes) vitamin D (cholecalciferol) vitamin K (phylioquinonoes, menaquinones) vitamin E (tocopherols) ```
73
what would happen if you give a patient with vitamin B1 deficiency glucose?
if you gave it without thiamine, would get degeneration of mammillary bodies in brain which would result in korsakoff's disease
74
what would be the symptoms of beriberi? what causes it? in what patient population would you see it?
seen in malnourished patients from the developing world will be short of breath, look warm and flushed weakness and loss of touch sensation in both feet due to thiamin deficiency that causes dilated cardiomyopathy
75
what are the symptoms of riboflavin deficiency?
cheliosis (fissuring at angle of mouth) dry skin, rash smooth, purple tongue not that important clinically because not deadly
76
why can we get niacin deficiency even if we can make it?
synthesis from tryptophan is very slow | can also have disorders where you don't make enough tryptophan
77
what are the symptoms of niacin deficiency?
pellagra: confusion, diarrhea, hyperpigmented skin rash that's photosensitive, death four Ds
78
what can vitamin B6 be used to treat?
TB - isoniazid
79
what would be the symptoms of pernicious anemia? what causes it?
caused by B12 deficiency would likely have autoimmune disease - destruction of parietal cells so can't absorb B12 fatigue anemic - smear shows megaloblasts - smear looks like someone with folate deficiency decreased sense of vibration in both feet
80
what are the symptoms of subacute combined degeneration?
``` increase in clumsiness decreased sense of vibration in both feet on physical examination history of autoimmune disease not anemic normal peripheral blood smear B12 deficiency ```
81
what is the cause of subacute combined degeneration?
get folate supplemenation but have megaloblastic anemia - the supplementation masks the effects of the anemia but the folate supplementation doesn't prevent spinal cord damage this damage is irreversable destroys areas of spinal cord that are responsible for vibration sense in lower extremities so still need B12 even though getting folate
82
why do people die of scurvy?
can't heal their wounds | lack of immune function
83
what is retinol necessary for?
reproduction | deficiency results in sterility
84
what are the symptoms/clinical presentation of vitamin A deficiency?
starts with night blindness | dry eyes - wrinkles and loss of shine
85
what can hypervitaminosis cause?
dry skin liver damage raised intracranial pressure
86
what would be the clinical presentation of vitamin D deficiency?
``` osteomalacia in adults = fractures in bone bone pain microfractures compression fractures rickets in children ```
87
what would be the clinical presentation of vitamin K deficiency?
premature infant in nicu begins bleeding spontaneously at venous puncture sites prothrombin time is prolonged could be internal bleeding
88
why do patients in the NICU have vitamin K deficiency?
born with sterile guts so can't get vitamin K

biochem term 2 quiz 4 (7 decks)

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