The liquid portion of blood known for its role in transportation is called what?

The liquid portion of blood responsible for transportation within the circulatory system is plasma. Plasma makes up about 55% of total blood volume and serves as a medium for transporting various substances, including nutrients, hormones, and waste products, throughout the body. It is a yellowish fluid that contains water, salts, and various proteins, which play critical roles in maintaining blood pressure and volume, as well as contributing to immune system function and blood clotting.

Serum, while also a component of blood, is the liquid that remains after the blood has clotted and therefore does not contain clotting factors like fibrinogen, making it less involved in the initial transportation functions. Hemoglobin is a protein found within red blood cells that specifically binds and transports oxygen and carbon dioxide, but it is not the liquid portion of blood itself. Albumin is one of the proteins found in plasma, contributing to oncotic pressure and transporting various substances, but it is not the entirety of the liquid component. Thus, plasma's comprehensive role in the overall transportation system within blood underscores its identification as the correct answer.