1. Bio-molecules 1. Structure of Water 2. Organic molecules الجزيئات العضوية Carbohydrates الكربوهيدرات Carbohydrates الكربوهيدرات Lipids الدهون Lipids الدهون Proteins البروتينات Proteins البروتينات Nucleic acids الأحماض النووية Nucleic acids الأحماض النووية

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

3. Water Molecule O-O- H+H+ H+H+ O-O- H+H+ H O-O- H+H+ H+H+ O-O- H+H+ H+H+ O-O- H+H+ H+H+ O-O- H+H+ H+H+ O-O- H+H+ H+H+

4. chargedpolar Water is an effective solvent because it forms hydrogen bonds with charged and polar covalent molecules. NaCl water hydrogen bonds negative oxygen hydrogen bonds partial positive hydrogen regions 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.

5. The solution المحلول : The solution المحلول : Is a liquid that is a completely homogeneous متجانس mixture of two or more substances. The solvent المـُذيب : The solvent المـُذيب : Is the dissolving agent The solute المُذاب : The solute المُذاب : Is the substance that is dissolved The aqueous solution المحلول المائى : The aqueous solution المحلول المائى : is the solution in which water is the solvent. Water is the solvent of life مذيب الحياة

6. Hydrophilic محب للماء (Glucose) : Hydrophilic محب للماء (Glucose) : Is any substance that has an affinity for water تحب الماء. Is any substance that has an affinity for water تحب الماء. Hydrophobic كاره للماء (Lipid) : Hydrophobic كاره للماء (Lipid) : لا تحب الماء Is the substances that have no affinity for water لا تحب الماء. Because they have non-ionic and non-polar covalent bonds. – Thus, water molecules cannot form hydrogen bonds with these molecules. Amphipathic كاره ومحب للماء (Phospholipid) : Amphipathic كاره ومحب للماء (Phospholipid) : Has end with affinity for water and the other end with no affinity for water Has end with affinity for water and the other end with no affinity for water Types of solutions

7. The acid: The acid: increases 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. Addition of an acid makes a solution more acidic. The base: The base: reduces Is any substance that reduces the hydrogen ion 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 + → H 2 O OH - H + Solutions with more OH - than H + are basic solutions. 1. Organisms are sensitive to changes in pH

8. pH = 7. – In a neutral solution, pH = 7. – Values for pH decline تقل as [H + ] increase. H + – While the pH scale is based on [H + ], values for [OH - ] can be easily calculated from the product relationship. – Acidic – Acidic solutions have pH values less than 7 and – basic – basic solutions have pH values more than 7. H + OH -. 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.