Chapter 3: Water

Water is essential for life. Life likely originated in water and water on Earth’s surface continues to make Earth habitable. Water serves as a solvent for the chemical reactions inside and outside of cells that support life and water constitutes 60–90% of cell mass. In the human body, most metabolic reactions happen in water and water serves as a lubricant in body fluids. In this section, we explore how the chemical structure of water leads to its remarkable chemical properties that sustain life.