Why is water often referred to as the 'universal solvent' in biological systems?

• A. Because it can dissolve only nonpolar substances.
• B. Because its polar molecules can dissolve a wide variety of substances.
• C. Because it is the only liquid found on Earth.
• D. Because it cannot form hydrogen bonds with other molecules.

Answer: (B)

Verified step by step guidance

1. Understand the concept of a 'universal solvent': A universal solvent is a substance that can dissolve a wide variety of solutes. In biological systems, water is often referred to as the universal solvent due to its unique chemical properties.
2. Examine the structure of water molecules: Water (H₂O) is a polar molecule, meaning it has a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. This polarity allows water to interact with and dissolve other polar substances and ionic compounds.
3. Explore hydrogen bonding: Water molecules can form hydrogen bonds with other polar molecules or ions. These bonds are relatively strong and help water break apart solutes into their individual components, facilitating dissolution.
4. Consider the biological significance: In biological systems, water's ability to dissolve a wide variety of substances is crucial for processes like nutrient transport, waste removal, and chemical reactions within cells.
5. Eliminate incorrect options: Water does not dissolve only nonpolar substances (it dissolves polar and ionic substances), it is not the only liquid found on Earth, and it can form hydrogen bonds with other molecules. The correct explanation is that water's polar molecules allow it to dissolve a wide variety of substances.