* Multiple Components: Blood plasma contains a wide variety of proteins, each with its own unique structure and function. These include albumin, globulins, fibrinogen, and many others.

* No Fixed Ratios: The relative proportions of different proteins in blood plasma can vary depending on factors like age, health, and diet.

* No Chemical Bonds: The proteins in blood plasma are not chemically bonded to each other. They are held together by weak interactions like hydrogen bonds and electrostatic forces.

Therefore, protein in blood meets the criteria of a mixture: it consists of multiple components that are not chemically bonded and can exist in varying proportions.