August 29, 2011 Biology 311C Lecture 3 Overview of Water: The molecule That Supports All of Life • Water is the biological medium on Earth. • Most cells are surrounded by water and cells themselves are about 70-95% water. • How do water molecules interact with each other: The oxygen is sharing a bit more around hydrogen. Oxygen has a partial negative charge and hydrogen has a partial positive charge. Hydrogen bonding is happening. The maximum amount of hydrogen bonding can occur is 4. • The bond between the hydrogen and oxygen in the individual molecule is covalent. • When table salt (NaCl) dissolves in water, what bonds are being broken and what new bonds are being formed? An ionic bond is broken. • If you have a positive ion, the oxygen part of the molecule points towards it. • Nonpolar molecules have no charge. • Water has hydrogen bonding and oil is hydrophobic so it repels water. • Oxygen and hydrogen are covalent do not share the electrons equally which makes it
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