Podcast
Questions and Answers
Why are Gla residues of prothrombin effective in chelating positively charged calcium ions?
Why are Gla residues of prothrombin effective in chelating positively charged calcium ions?
What is the role of the prothrombin-calcium complex in blood clotting?
What is the role of the prothrombin-calcium complex in blood clotting?
Which foods are rich sources of Vitamin K?
Which foods are rich sources of Vitamin K?
What is a primary reason newborns are at risk for Vitamin K deficiency?
What is a primary reason newborns are at risk for Vitamin K deficiency?
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What dose of Vitamin K is recommended as a prophylactic measure for newborns?
What dose of Vitamin K is recommended as a prophylactic measure for newborns?
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What are some potential toxic effects of prolonged administration of synthetic Vitamin K (menadione) in infants?
What are some potential toxic effects of prolonged administration of synthetic Vitamin K (menadione) in infants?
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Study Notes
Prothrombin and Platelet Interaction
- The Gla residues of prothrombin have a strong chelating effect on positively charged calcium ions due to their two adjacent, negatively charged carboxylate groups.
- The prothrombin-calcium complex binds to phospholipids on the surface of platelets, essential for blood clotting.
- Attachment to platelets increases the rate of proteolytic conversion of prothrombin to thrombin.
Vitamin K Distribution and Requirement
- Vitamin K is found in various food sources, including cabbage, kale, spinach, egg yolk, and liver.
- The bacteria in the gut also synthesize vitamin K.
- The recommended daily intake of vitamin K is 120 µg for adult males and 90 µg for adult females.
Vitamin K Deficiency in Newborns
- Newborns have sterile intestines, lacking the bacteria that synthesize vitamin K.
- Human milk provides only about one-fifth of the daily requirement for vitamin K.
- A single intramuscular dose of vitamin K is recommended for newborns as prophylaxis against hemorrhagic disease.
Vitamin K Toxicity
- Prolonged administration of large doses of synthetic vitamin K (menadione) can cause hemolytic anemia and jaundice in infants.
- Toxic effects occur due to damage to red blood cell membranes.
- Synthetic vitamin K is no longer used to treat vitamin K deficiency.
- There is no established upper limit for vitamin K consumption.
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Description
This quiz covers the interaction of prothrombin and platelets, and the role of vitamin K in blood clotting. It explores the binding of prothrombin to calcium and phospholipids, and the conversion of prothrombin to thrombin.
