The basic event in the formation of a blood clot is the change of:
Thrombin to prothrombin.
Fibrinogen to fibrin.
Vitamin K to prothrombin.
Fibrin to fibrinogen.
The Correct Answer is B
This is because fibrinogen is a soluble protein in the blood plasma that is converted to insoluble fibrin strands by the enzyme thrombin during blood clotting. Fibrin forms a mesh-like network that traps platelets and other blood cells to form a clot.
Choice A is wrong because thrombin is not converted to prothrombin, but rather prothrombin is converted to thrombin by another enzyme called prothrombinase.
Choice C is wrong because vitamin K is not converted to prothrombin, but rather vitamin K is required for the synthesis of prothrombin and other clotting factors in the liver.
Choice D is wrong because fibrin is not converted to fibrinogen, but rather fibrinogen is converted to fibrin as explained above.
Normal ranges of fibrinogen in the blood are 200 to 400 mg/dL.
Normal ranges of prothrombin time (a measure of how long it takes blood to clot) are 11 to
13.5 seconds.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
This is because it is an example of a positive feedback loop, which amplifies the change and moves the system away from its normal state.
A negative feedback loop is a mechanism that reverses a deviation from the set point and maintains homeostasis.
Choice A is wrong because increasing heart rate and force of contraction when blood pressure falls is a negative feedback loop that restores blood pressure to normal.
Choice B is wrong because secreting insulin after a meal to return blood sugar concentration toward normal is a negative feedback loop that regulates glucose levels.
Choice D is wrong because shivering when body temperature falls below normal is a negative feedback loop that increases heat production and raises body temperature.
Normal ranges for blood pressure are 90/60 mmHg to 120/80 mmHg, for blood glucose, are 70 mg/dL to 140 mg/dL, and for body temperature are 36.5°C to 37.5°C or 97.7°F to 99.5°F.
Correct Answer is C
Explanation
The conversion of fibrinogen to fibrin by thrombin is the final step in the formation of a blood clot.
Fibrin is a protein that forms a net-like structure that traps platelets and other blood cells, making the clot stronger and more durable.
Choice A is wrong because the formation of a prothrombin activator is the first step in the formation of a blood clot.
A prothrombin activator is a complex of enzymes that converts prothrombin to thrombin.
Choice B is wrong because the conversion of prothrombin to thrombin by the prothrombin activator is the second step in the formation of a blood clot.
Thrombin is an enzyme that converts fibrinogen to fibrin.
Choice D is wrong because tissue damage is not a step in the formation of a blood clot, but a trigger for the clotting process.
When blood vessels are injured, they release substances that activate platelets and clotting factors.
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