Blood proteins, also known as plasma proteins, are present in the blood. They serve many functions, such as the transportation of lipids, vitamins and minerals, and hormones, and help immune system functions.  Albumin and globulin help maintain the oncotic plasma pressure (pressure induced by proteins in a blood vessel's plasma that causes a pull of fluid back into the capillary) and assist as a carrier for lipids and hormones. Immunoglobulins help fight infection.