2. Biomolecules

3. The Water Life exists on Earth because of the abundant liquid water.
Water has been referred to as the universal solvent.
Aqueous solutions: are solutions that have materials dissolved in water)
So, it has slightly positive and a slightly negative sides.

4. Water Molecule O- H+ H

6. The Universal Solvent
Water is an effective solvent because it forms hydrogen bonds with charged and polar covalent molecules.
For example, when a crystal of salt (NaCl) is placed in water, the Na+ cations form hydrogen bonds with partial negative oxygen regions of water molecules. While, the Cl- anions form hydrogen bonds with the partial positive hydrogen regions of water molecules.

7. The Universal Solvent (Video)

8. Water is the solvent of life
The solution:
Is a liquid that is a completely homogeneous mixture of two or more substances.
A sugar cube in a glass of water will dissolve to form a uniform mixture of sugar and water.
The solvent:
Is the dissolving agent
The solute:
Is the substance that is dissolved
In the above example, water is the solvent, and sugar is the solute.
The aqueous solution:
is the solution in which water is the solvent.

9. Types of solutions Hydrophilic (Glucose):
Is any substance that has an affinity for water .
Hydrophobic (Lipid):
Is the substances that have no affinity for water. Because they have non-ionic and non-polar covalent bonds.
Thus, water molecules cannot form hydrogen bonds with these molecules.
Amphipathic (Phospholipid):
Has end with affinity for water and the other end with no affinity for water
The Hydrophobic molecules are the major ingredients of cell membranes.

10. Organisms are sensitive to changes in pH
The acid:
Is a substance that increases the hydrogen ion (H+) concentration in a solution.
When hydrochloric acid is added to water, hydrogen ions dissociate تنفصل from chloride ions:
HCl H+ + Cl-
Addition of an acid makes a solution more acidic.
The base:
Is any substance that reduces the hydrogen ion (H+) concentration in a solution.
Some bases reduce H+ directly by accepting hydrogen ions.
Other bases reduce H+ indirectly by releasing OH- that combines with H+ to form water.
NaOH → Na+ + OH- OH- + H+ → H2O
Solutions with more OH- than H+ are basic solutions.`

11. PH Scale In a neutral solution, pH = 7.
Values for pH decline تقل as [H+] increase.
While the pH scale is based on [H+], values for [OH-] can be easily calculated from the product relationship.
Acidic solutions have pH values less than 7 and
basic solutions have pH values more than 7.
A small change in pH actually indicates a change in H+ and OH-.
Most biological fluids have pH values in the range of 6 to 8.