CBSE Class 10 Answered

Blood is more viscous than water.  This is important for maintaining a constant flow through the blood vessels. The flow properties of blood are adapted to flow effectively through tiny capillary blood vessels with less resistance than plasma by itself.

Blood carries the cells which carry out unique important functions. The RBCs carry the respiratory pigment which help in transport of respiratory gases, WBCs are important in defense mechanism of the body and platelets are important in blood clooting. Cells are not present in water.

The plasma of blood contains several important proteins, all of which are absent in water. (Blood plasma contains 8% blood plasma proteins, and trace amounts of other materials. Plasma circulates dissolved nutrients, such as glucose, amino acids, and fatty acids (dissolved in the blood or bound to plasma proteins), and removes waste products, such as carbon dioxide, urea, and lactic acid.)