CAMLPR Chemistry Practice Test

Coagulation relies on a soluble plasma protein that becomes insoluble to form a fibrin mesh. The protein involved is fibrinogen, produced by the liver. When the coagulation cascade activates thrombin, thrombin cleaves fibrinogen to yield insoluble fibrin strands that polymerize to form the clot, with final stabilization by factor XIII crosslinking. Other listed proteins have different roles: albumin helps maintain osmotic pressure and fluid balance, immunoglobulins are antibodies, and transferrin transports iron. Since the key step in clot formation is the conversion of the soluble fibrinogen precursor into the insoluble fibrin network, fibrinogen is the correct choice.