What is the role of water in blood?

• A. Acts as a nutrient source for cells.
• B. Primarily stores hormones in plasma.
• C. Acts as a solvent, suspends formed elements, and dissolves proteins and solutes.
• D. Initiates immune responses.

Answer: (C)

Water in blood acts as the solvent and medium that enables transport of many substances. The plasma portion is largely water, which suspends formed elements—red blood cells, white blood cells, and platelets—and dissolves a wide array of proteins and solutes. This solvation supports the transport of nutrients, electrolytes, hormones, wastes, and gases, and it allows plasma proteins such as albumin and fibrinogen to remain dissolved and function, helping to maintain blood volume and osmotic pressure. Water also participates in chemical reactions and helps stabilize blood temperature. It is not primarily a nutrient source, nor a storage site for hormones, and it does not initiate immune responses; those roles belong to nutrients, endocrine signaling, and immune cells, respectively. The solvent properties of water in plasma are essential for circulation and homeostasis.