1. Chapter 2: Biochemistry
Section 2: Water and Solutions

2. Storage of Energy
Many organisms release excess heat through water evaporation.

3. Storage of Energy
In organisms, this ability to control temperature enables cells to maintain a constant internal temperature when the external temperature changes.
In this way, water helps cells maintain homeostasis.

4. Cohesion and Adhesion
Cohesion is attraction between substances of the same kind.
Because of cohesion, water and other liquids form thin films and drops.

5. Cohesion and Adhesion
Molecules at the surface of water are linked together by hydrogen bonds like a crowd of people linked by holding hands.
This attraction between water molecules causes a condition known as surface tension.

6. Cohesion and Adhesion
Adhesion is an attraction between different substances.
Adhesion powers a process, called capillary action, in which water molecules move upward through a narrow tube, such as the stem of a plant.

7. Aqueous Solutions
A solution is a mixture in which one or more substances are evenly distributed in another substances. =

8. Aqueous Solution
Many important substances in the body have been dissolved in blood or other aqueous fluids.
Because these substances can dissolve in water, they can more easily move within and between.

9. Polarity
The polarity of water enables many substances to dissolve in water.
When ionic compounds are dissolved in water, the ions become surrounded by polar water molecules.

10. Polarity
The resulting solution is a mixture of water molecules and ions.
When sodium chloride, NaCl, is dissolved in water, sodium ions, Na+, and chloride ions, Cl-, become surrounded by water molecules, H2O.

11. Nonpolar
Nonpolar molecules do not dissolve well in water.

12. Non-polar
The inability of non-polar molecules to dissolve in polar molecules is important to organisms.
For example, the shape and function of cell membranes depend on the interaction of polar water with non-polar membrane molecules.

13. Acid and Bases
Compounds that form hydrogen ions when dissolved in water are called acids.
When an acid is added to water, the concentration of hydrogen ions in the solution is increased above that of pure water.

14. Acid and Bases
Compounds that reduce the concentration of hydrogen ions in a solution are called bases.
Many bases form hydroxide ions when dissolved in water.

15. pH Scale
The pH scale measures the concentration of hydrogen ions in a solution.
Neutral
Acid
Base