Question

Prothrombin is found in
A.Intestine and helps in cellulose digestion
B.Liver and helps in production of bile
C.Blood and gives red colour to blood
D.Blood and helps in blood clotting

Answer 1

Hint: When the prothrombin period (PT) is high, it takes longer for the blood to clot (17 seconds, for example). Typically a high PT means that significant liver damage or cirrhosis is present. Typically a high PT means that significant liver damage or cirrhosis is present.

Complete answer:
Prothrombin is a plasma protein that in the presence of thromboplastin released by platelets at the injury site, is converted into thrombin. The thrombin then transforms fibrinogen protein into insoluble fibrin and thus helps to clot blood. Prothrombin (Factor II) is a liver synthesized zymogen and is vitamin K dependent. It forms thrombin when prothrombin is activated (Factor IIa). Thromboplastin (TPL) or thrombokinase is a plasma mixture of both phospholipids and tissue factor that helps blood coagulation by catalyzing prothrombin to thrombin conversion. Historically, thromboplastin was a laboratory reagent used to monitor prothrombin cycles, typically obtained from placental sources (PT).

Prothrombin is activated by an enzyme complex attached to the membrane. Prothrombinase assembles on membranes containing phosphatidylserine by reversible interactions between serine proteinase Xa and the protein cofactor Va.

Hence, the correct answer is option (D)

Note: Hypoprothrombinemia, a prothrombin deficiency, is characterized by a tendency towards excessive bleeding. A lack of vitamin K, which is essential for the synthesis of prothrombin in liver cells, is typically associated with it.