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HUN 4221 Exam 2 > Vitamin K > Flashcards

Vitamin K Flashcards

1
Q

Who was Henrik Dam and Edward Doisy?

A

Won nobel peace prize in physiology/medicine for:
Dam- discovery of vitamin K
Doisy- his discovery of the chemical nature of vitamin k.

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2
Q

What are the biologically active forms of Vitamin K/food forms?

A

Phylloquinone = plants
Menaquinone-4 (MK-4) = bacteria (fermented cheeses)
Menaquinone-4 (MK-7) = bacteria (fermented soy products)
Menadione = synthetic

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3
Q

How is Vitamin K transported?

A

In lipoproteins VLDL –> LDL –> HDL

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4
Q

How are lipoproteins taken up?

A

By receptor mediated endocytosis

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5
Q

How is Vitamin K stored?

A

In liver in the form as menaquinone.
Limited storage = 50-100 micrograms
Has a rapid turnover- short half life about 1.5 days

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6
Q

how is Vitamin K excreted?

A

In feces or urine

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7
Q

What is a function of Vitamin K?

A

Necessary for the posttranslational carboxylation of glutamic acid residues in proteins to form gamma-carboxyglutamic acid residues.

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8
Q

What are Glutamic (Gla) residues needed for?

A

They enable the protein to bind to calcium and interact with other proteins.
These interactions are necessary for blood clotting and bone mineralization

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9
Q

What are the blood clotting proteins and which promote coagulation and which inhibit coagulation?

A

Promote coagulation
Factor II (Prothrombin)
Factors VII, IX, X

Inhibit Cogulation
Protein C, S, Z

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10
Q

Where are the blood clotting proteins synthesized?

A

In the liver and have 10-13 Gla residues

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11
Q

What are the functions of Gla residues?

A

Enables Ca++ mediated binding of the proteins to the negatively charged phospoholipid surfaces provided by blood platelets and endothelial cells at the site of injury

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12
Q

What is a Prothrombin Time Test?

A

In vitro test of vitamin K status

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13
Q

What does a Prothrombin Time Test measure?

A

Time required for a fibrin clot to form after adding calcium and other substances to citrated plasma
Normal time = 11-14 seconds
Greater than 25 seconds are associated with major bleeding and vitamin K deficiency

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14
Q

What are antagonists of Vitamin K?

A

Dicumarol
Warfarin (Coumadin) (used as therapy to prevent thromboembolisms such as in strokes and myocardial infractions) (comes from Wisconsin Alumin research…)

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15
Q

What does Anticoagulants such as Warfarin inhibit?

A

Inhibits quinone reductase (slide 23)

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16
Q

What kind of foods is Vitamin K found in?

A

Widely distributed.

17
Q

How is Vitamin K absorbed in the intestine?

A

Via micelles then into chylomicrons which exit the cell and enter the lymph system.

18
Q

How is Vitamin K metabolized in the liver?

A

Phylloquinone or menaquinone inside the chylomicron enter the hepatocyte
Phyloquinone and menaquinone are attached to VLDL and exit the liver and are transported to peripheral tissues
Menadione can by converted to menaquinone with the alkylation of an isoprenyl group.

19
Q

What factors participate in formation of fibrin clot?

A

Prothrombin and factors VII, IX, X

20
Q

Gla-containing blood proteins are zymogen forms of what?

A

Serine proteases

21
Q

Key advice to patients on dicumarol drugs?

A

To maintain usual dietary pattern and report any planned changes in diet or multivitamin usage

22
Q

Where are the vitamin k dependent proteins located in?

A

Bone, cartilage, and dentine

23
Q

What are the vitamin k dependent proteins?

A

Osteocalcin (bone Gla protein)

Matric Gla protein

24
Q

What is the major component of bone?

A

Osteoclacin

25
Q

Where are osteoclacins secreted by?

A

By osteoblasts during bone matrix formation

26
Q

Osteoclacin function?

A

Regulaor of bone mineralization

27
Q

What does Osteoclain adhere to?

A

Hydroxyapatite

28
Q

How many Gla residues does osteoclacin have in order to bind to calcium?

A

3

29
Q

What is MGP?

A

Matric Gla Protein

30
Q

What is MGP associated with?

A

Mobilization of bone calcium

31
Q

In vitamin K deficiency, undercarboxylation of MGP leads to what?

A

Increases calcification of atherosclerotic lesions

32
Q

What are the indicators of inadequate vitamin k

A

Undercarboxylated prothrombin-liver
–protein induced by vitamin k absence (PIVKA)
Undercarboxylated osteoclacin (ucOC)-bone

33
Q

Vitamin K deficiency

A

uncommon in helathy adults
seen in people with GI malabsorptive disorders
Newborns are particularly at risk and are given an injection at birth

34
Q

What is the RDA for Vit K?

A

None, we can make it.

35
Q

Vit K toxicity

A

no upper limit
phylloquinone and menaquinone are non toxic
menadione can be toxic
—liver damage
—in infants: hemolytic anemia, hyperbilirubinemia, jaundice

HUN 4221 Exam 2 (7 decks)

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