Universal Solvent

• Many substances (gases, waste compounds, inorganic ions, and enzymes) dissolve in water due to their polarity or their dissociation to give polar ions
• Essential transport medium for polar molecules and ions; main component of blood, tissue fluid, urine, and phloem sap
• Facilitates metabolic reactions as soluble reactants move freely in the aqueous cell cytoplasm
• Aquatic organisms and plants can absorb soluble O_2 for aerobic respiration and CO_2 for photosynthesis, as well as soluble mineral ions (also non-aquatic plants through soil water via roots)