Serum albumin, the main protein of plasma, has a good binding capacity for water, Ca(2+), Na(+), K(+), fatty acids, hormones, bilirubin and drugs. Its main function is the regulation of the colloidal osmotic pressure of blood. Plasma. In the red-eared slider turtle, there are two forms of albumin, ALB-1 and ALB-2. Belongs to the ALB/AFP/VDB family.