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Biochem + Metabolism > Vitamins > Flashcards

Vitamins Flashcards

1
Q

Is Vitamin A water soluble or fat soluble?

A

fat

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2
Q

All vit A are classified as

A

retinoids

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3
Q

What are the 3 pre-formed forms of Vit A?

A

-Retinol
-Retinal
-Retinoic acids

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4
Q

Which form of Vit A is important in vision?

A

Retinal

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5
Q

What is the active form of Vit A in transcriptional regulation?

A

retinoic acid

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6
Q

What are precursors to Vit A?

A

carotenoids

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7
Q

What form of Vit A can carotenoids be cleaved in to?

A

retinal

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8
Q

What are the two forms of retinoic acid?

A

all-trans retinoic acid and 9-cis-retinoic acid

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9
Q

What form of vit A is only found naturally in animal products?

A

pre-formed retinoids

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10
Q

where are all the provitamin A found?

A

carotenoids are found in plants

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11
Q

What must occur before vit A can be absorbed?

A

-provitamin a are cleaved into retinal via carotene dioxygenase
-retinal is reduced to retinol, esterified and secreted into chylomicrons together with dietary retinol

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12
Q

Why must retinoids be packaged into chylomicrons?

A

because they are fat soluble so they must be attached to a lipoprotein in order to cross the intestinal membrane

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13
Q

In what form is retinol stored?

A

as retinyl esters

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14
Q

Where is retinol stored?

A

the liver

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15
Q

How is retinol transported in blood?

A

via retinol binding proteins

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16
Q

What happens to retinol once it is carried to tissues via RBPs?

A

it is oxidized to retinoic acid (active form)

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17
Q

Explain the role of retinal in vision

A
  • In the retina, when light strikes rhodopsin (contains retinal) it isomerizes 11-cis-retinal to 11-trans-retinal, signal then passes to a g-protein (transducin) triggering a series of events. the rod hyper polarizes which leads to the perception of light
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18
Q

What is the mechanism of action of retinoic acid?

A

both all-trans and 9-cis-retinoic acid bind to nuclear receptors, which then alters gene expression

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19
Q

What are the two retinoic acid receptor families?

A

retinoic acid receptor and retinoic acid x receptors

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20
Q

Which receptor binds BOTH all-trans and 9-cis- retinoic acid?

A

retinoic acid receptors

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21
Q

Which receptor binds ONLY 9-cis-retinoic acid?

A

retinoic acid x receptor

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22
Q

although not common, list 5 results of vit A deficiency

A

-blindness
-increased susceptibility to infectious diseases
-maternal mortality and poor pregnancy outcomes
-decreased growth rates and bone development in young
-reptiles and birds: conjunctivitis, periocular inflammation

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23
Q

True/false: vit a deficiency is more of a problem/common than toxicity?

A

false

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24
Q

What is the main result of Vit. A toxicity?

A

cell lysis and tissue damage

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25
Q

What is hypervitaminoisis A usually related to?

A

Dietary reasons

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26
Q

What is the most common sign of hypervitaminosis A?

A

skeletal abnormalities/ bone issues

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27
Q

Is Vit D water or fat soluble?

A

fat

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28
Q

Is Vit D strictly a vitamin? if not, why not?

A

No, because it can be synthesized in the skin with UV light exposure.

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29
Q

What is the main biologic function of the active form of Vit D

A

It acts as a hormone in the regulation of calcium absorption and homeostasis

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30
Q

What is the active form of Vit D?

A

calcitriol

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31
Q

What are the major class of enzymes that active Vit D?

A

cytochrome proteins (hydroxylases)

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32
Q

What two organs are involved in the activation of Vit D?

A

liver and kidney

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33
Q

What are the two dietary sources of Vit D?

A

Ergocalciferol (D2): found in some plants and fungi
Choleocalciferol (D3): animal sources

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34
Q

Where is dietary vit D absorbed?

A

intestine

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35
Q

How is both dietary and synthesized vit D transported in the blood?

A

Vitamin D binding proteins (DBP)

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36
Q

What are the 3 target organs of vit D?

A

kidney, intestine, bone

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37
Q

How are calitriol actions carried out/mediated?

A

the nuclear receptor (VDR)

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38
Q

How does calcitriol regulate calcium homeostasis?

A

Maintains serum concentration by:
-Increases calcium absorption in the intestine
-reduces excretion of calcium by stimulating reabsorption in the distal renal tubules
-mobilization of calcium from bone

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39
Q

What are the 4 other biologic actions of calcitriol outside of calcium mediation?

A

-cell differentiation and proliferation
-synthesis and secretion of parathyroid and thyroid hormones
-immune function
-bone development and remodeling

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40
Q

What are the key points of calcitriol production (aka Vit D activation)?

A

-up-regulation of low serum calcium and phosphate
-self regulation by stimulating 24-hydroxylase (inactivation) and inhibiting 1-hydroxylase

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41
Q

What are the main signs of Vit D deficiency?

A

hypocalcemia, muscle weakness, immune dysfunction, bone issues

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42
Q

What are the signs of hypervitaminosis D?

A

Hypercalcemia, calcification of soft tissues, kidney disease, uroliths

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43
Q

Calculate a toxic dose of Vit D

A

toxic dose: >100ug/kg
40IU=1ug
most supplements are 400IU

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44
Q

Is Vit E water or fat soluble?

A

fat

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45
Q

Describe the antioxidant action of Vit E

A

Acts as a lipid soluble antioxidant in cell membranes and for serum lipoproteins by free radical scavenging, it will donate an H atom to radicals, this in turn forms an oxidized radical which can be reduced by other antioxidants

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46
Q

What is the active form name of Vit E

A

Tocopherol

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47
Q

How do ROS affect the phospholipid bilayer?

A

affects the structure and permeability

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48
Q

Which fatty acids are sensitive to oxidative damage?

A

unsaturated fatty acids

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49
Q

Why would you supplement vit E if an animal routinely is supplemented omega- 3 fatty acids?

A

Since unsaturated fatty acids are more susceptible to free radical damage, vit. e supplementation will help prevent degradation.

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50
Q

List two ways tocopherol radicals (post antioxidant actions) can be addresses?

A

-reduced back by other antioxidants
-can be conjugated to then be excreted in bile

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51
Q

Why is Vit E less likely to result in toxicity compared to other fat soluble vitamins?

A

Because it can be routinely conjugated and excreted in bile

52
Q

What disease in lambs and calves can be caused by vitamin E deficiency?

A

white muscle disease

53
Q

Describe white muscle disease

A

because of the deficiency, free radicals produced by muscle use will build. free radials will bind to calcium. Calcium will then deposit and cause white streaks in the muscles

54
Q

Is vitamin K water or fat soluble?

A

fat

55
Q

How was vitamin K discovered?

A

result of investigation into the cause of a bleeding disease in cattle and chickens

56
Q

What is the main function of vit K?

A

required for blood clotting

57
Q

What is the active form of vit k?

A

hydroquinone

58
Q

is the active form of vit k water or fat soluble?

A

water!

59
Q

What is the role of hydroquinone in clotting protein formation?

A

It is required for the post-translational modification of glutamate residues in clotting proteins

60
Q

carboxylated glutamate (Gla) has the ability to do what?

A

chelate calcium

61
Q

What does binding calcium permit clotting proteins to do?

A

promotes the binding of the proteins to to phospholipid surfaces inside blood vessels

62
Q

What are two vit k antagonists?

A

Dicumarol and Warfarin

63
Q

What important information do you need to you treat rodenticide poisoning?

A

Which type of rodenticide it is

64
Q

How does warfarin inhibit clotting?

A

It inhibits 2,3 epoxide reductase (VitK reductase)

65
Q

Describe the hepatic vit k cycle

A

Vit K -> hydroquinone-> 2,3 epoxide via 2,3 epoxide reductase -> vitamin K

66
Q

What kind of inhibitor is warfarin and dicumarol?

A

competative

67
Q

For what species is Ascorbic acid a vitamin?

A

primates, guinea pigs, bats, most fish, songbirds

68
Q

What pathway synthesizes ascorbic acid?

A

Uronic acid pathway

69
Q

What are the 3 main actions of vitamin C?

A

-Cofactor for hydroxylation reactions
-Powerful reducing agent
-Enhances intestinal absorption of iron

70
Q

What reactions is ascorbic acid needed for?

A

-Dopamine hydroxylase
-proline and lysine hydroxylases
-carnitine synthesis

71
Q

How does ascorbic acid enhance the absorption of iron?

A

It redices Fe3+ to the more easily absorbed Fe2+ form

72
Q

Is Ascorbic acid water or fat soluble?

A

water

73
Q

What is the main antioxidant activity of ascorbic acid?

A

It is the primary defense against aqueous radicals in the blood?

74
Q

What enzyme converts L-ascorbate back to ascorbic acid?

A

glutathione peroxidase

75
Q

What is the main disease associated with vit c deficiency?

A

scurvy

76
Q

What are the main signs of scurvy?

A

-gum recession and bleeding
-bruising
-fragility of capillaries
-bone fracture
-psychological changes

77
Q

Is thiamine (B1) water or fat soluble?

A

water

78
Q

What is the key role of thiamin?

A

plays a key role in carbohydrate metabolism

79
Q

What are the two main reactions that require thiamin?

A

-Oxidative/reduction reactions
-Transketolase reactions (ex HMS)

80
Q

What typically causes thiamin deficiency?

A

thiamases

81
Q

What are thiaminases and where are they mainly found?

A

They degrade thiamin and they are found in raw rish/shellfish (produced by microbes)

82
Q

Is riboflavin (B2) water or fat soluble?

A

water

83
Q

What are the two coenzymes riboflavin is a precursor for?

A

FMN and FAD

84
Q

What are the roles of flavin coenzymes?

A

they are electron carries in oxidation/reduction rxns

85
Q

What enzyme is uric acid formation is dependent on a rioboflavin derivative?

A

xanthine oxidase

86
Q

Why are there no serious signs of riboflavin deficiency?

A

Because the body is very efficient in its use. Once it is release by catabolism of enzymes it is quickly incorporated into new ones

87
Q

Is niacin water or fat soluble?

A

water

88
Q

What are the two forms of vit B3

A

Niacin and niacinamide

89
Q

Why is niacin so critical?

A

It is a component of NAD and NADP

90
Q

What reactions are niacin derivatives part of?

A

oxidation/reduction rxns

91
Q

Where is niacin mainly absorbed?

A

small intestine

92
Q

Why is niacin not strictly a vitamin?

A

niacinamide can be synthesized from tryptophan in the liver of most mammals

93
Q

What amino acid is niacin a derivative of?

A

tryptophan

94
Q

what species CAN NOT synthesize niacin?

A

cats

95
Q

Which vitamin and what form would you use as a treatment for inflammatory or autoimmune skin conditions in dogs such as cutaneous lupus or pemphigus

A

niacin, specifically niacinamide

96
Q

Why would you NOT use specifically niacin as a supplement in animals?

A

Because it has a different profile to niacinamide and can cause signs such as skin flushing, dizziness, tachycardia, nausea, liver damage at high doses

97
Q

What are the 2 main coenzymes derived from pentothenic acid?

A

CoA
4-phosphopentatheine

98
Q

Is pentothenic acid (Vit B5) water or fat soluble?

A

water

99
Q

What component provides coenzyme A with its sulfur group?

A

cysteine

100
Q

What 2 types of pathways utilize CoA? give examples

A

-Carbohydrate metabolism: Acetyl CoA, Succinyl CoA, Propionyl CoA
-Lipid metabolism: Acyl-CoA, HMG-CoA

101
Q

Is pentothenic acid deficiency common or rare?

A

rare

102
Q

Is Biotin (B7) water or fat soluble?

A

water

103
Q

What rxns is biotin a coenzyme in? (3)

A

-Acetyl CoA carboxylase (fatty acid biosynthesis)
-Propionyl CoA carboxylase (propionate to succinyl coa)
-Pyruvate carboxylase (pyruvate to OAA)

104
Q

Where can biotin be synthesized?

A

microflora in the intestine

105
Q

Why can raw egg white ingestion be a problem?

A

It contains avidin which will bind to biotin in the gut and prevent absorption

106
Q

Which vitamin can be used as a reagent in biochemical assays to detect proteins and nucleic acids?

A

Biotin

107
Q

What has to happen to biotin before it can be used as a coenzyme in carboxylation rxns?

A

it must be carboxylated itself

108
Q

What is the active form of biotin?

A

carboxybiotin

109
Q

What is the most common active form of B6

A

Pyridoxal phosphate

110
Q

What rxns (4) require vit B6 (pyridoxal phosphate)

A

-Glycogen phosphorylase
-AA metabolism
-Heme/porphyrin metabolism (delta-ALA synthase)
-Niacin synthesis from tryptophan

111
Q

What neurotransmitter synthesis requires pyridoxal phosphate?

A

GABA

112
Q

Formation of N5,N10 methylene THF requires what coenzyme?

A

Vit B6

113
Q

Where does cobalamin get its name?

A

the cobalt in the center of the porphyrin ring

114
Q

Where do you get cobalamin (Vit B12)?

A

Animal sources only

115
Q

What synthesizes Vit B12

A

microorganisms

116
Q

What causes the color of cobalamin?

A

the porphyrin ring

117
Q

Where is Vit B12 absorbed?

A

distal intestine

118
Q

What glycoprotein is required for cobalamin absorption?

A

Intrinsic factor

119
Q

Where is intrinsic factor made?

A

gastric parietal cells and by pancreatic ductular cells in dogs and cats

120
Q

What protein allows B12 uptake by the liver?

A

transcobalamin II (TCII)

121
Q

Where can cobalamin be stored?

A

the liver

122
Q

What must cobalamin be bound to to be stored?

A

transcobalamin I (TCI)

123
Q

What two rxns require cobalamin?

A

-proprionate->methylalonyl CoA ->succinyl CoA
-homocysteine -> methionine which releases THF which is needed for nucleic acid synthesis

124
Q

What are 5 causes of B12 deficiency?

A

-Dietary
-Gastric disease
-Pancreatic disease
-Ileal disease
-Liver Disease

125
Q

What are the main diseases that in turn cause B12 deficiency

A

-Resection or IBD
-Overgrowth of cobalamin binding bacteria

126
Q

What disease can result from vit B12 deficiency

A

Megaloblastic anemia

Biochem + Metabolism (15 decks)

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