363139
When normal platelets are activated , as may occur at sites of vascular injury , phosphatidylserine ( PS ) in the inner leaflet of the platelet membrane is transported to the outer membrane surface of the platelet , where it provides a binding site for plasma protein complexes , such as factor VIIIa-IXa ( tenase ) and factor Va-Xa ( prothrombinase ) , that are involved in the conversion of prothrombin to thrombin .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 None