Final answer:
The statement is True; oxygen dissolved in blood plasma plays a secondary and protective role in providing an oxygen reserve for tissues with sudden high demand.
Step-by-step explanation:
The statement that the amount of oxygen dissolved in the blood plasma has a secondary and protective role is True. While the primary method of oxygen transport in the blood is via hemoglobin within red blood cells, a small amount of oxygen is also dissolved in the blood plasma. This serves a protective role by providing an oxygen reserve that can be used when tissues suddenly demand more oxygen, especially since hemoglobin-bound oxygen can be insufficient during conditions of extreme stress or activity. Moreover, when discussing the functionality of the circulatory system, it's worth mentioning that plasma proteins do not typically cross the capillary cell membrane through facilitated diffusion; they are too large and instead are retained within the capillaries to maintain colloid osmotic pressure.