Step 1: Understanding plasma proteins.
Plasma proteins are proteins present in blood plasma and play important roles in osmotic balance, immunity, and blood clotting.
Step 2: Identifying true plasma proteins.
Albumin maintains osmotic pressure.
Prothrombin and fibrinogen are clotting factors present in plasma.
Step 3: Identifying the exception.
Thromboplastin is not a plasma protein; it is released from damaged tissues and platelets during blood clotting.
Step 4: Conclusion.
Therefore, thromboplastin is not classified as a plasma protein.