Final answer:
Albumin is the predominant plasma protein responsible for creating colloidal osmotic pressure in the blood, which is vital for fluid balance and blood pressure maintenance.
Step-by-step explanation:
The molecule principally responsible for creating colloidal osmotic pressure, also known as oncotic pressure, in the bloodstream is albumin. Albumin is the most abundant plasma protein and exerts a significant osmotic force, which helps to retain water within the circulatory system. This osmotic pressure is essential for maintaining blood volume and pressure and for facilitating the reabsorption of fluid into capillaries from surrounding tissues. In contrast, glucose, hemoglobin, and insulin, although important for various biological functions, do not have the same impact on colloidal osmotic pressure as albumin does.