Question

Prothrombin is a clotting factor that is normally present in the bloodstream. When a blood vessel is cut, prothrombin in the damaged area becomes activated and is converted to thrombin. Thrombin is an enzyme that acts to (1) promote the formation of fibrin fibers that begin to form a blood clot, and (2) convert additional prothrombin to thrombin. (a) What type of feedback loop is this? (b) What is the advantage of this type of feedback loop in this situation? (c) The formation of the blood clot halts the loss of blood and allows eventual restoration of blood volume to normal levels. In this wider sense, what type of feedback loop is represented?

Answer 1

B. Positive feedback

• It is defined as response that result in amplification or enhancement of the stimulus.
• Prothrombin is inactive enzyme. When there is damage to blood vessel then it is converted to thrombin. Throbbing then acts on prothrombin and enhance it's conversion to thrombin. Therefore it is positive feedback.

C. Negative feedback

• Negative feedback is defined as process which decreases the stimulus that caused it's activation.
• When there is damage to blood vessel, then blood is lost. This activated blood coagulation, which then decreases blood loss.