1	THE LIFE OF THE CELL
2	"Atom – smallest unit of..." Atom – smallest unit of an element
3	Types of Bonds: . Covalent bonds – atoms share electrons Polar covalent - electrons are closer to one atom than the other Nonpolar covalent - electrons are shared equally . Ionic bond – formed by ions Ion – atom that has either gained or lost an electron Formed by equal and opposite charges of ions
4	Types of Bonds 3. Hydrogen bond – slight positive charge on H⁺, resulting from polar covalent bond, attracted to slight negative charge
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6	WATER Water is the single most abundant component of cells and organisms. 75-85% of a cell is water (10-20 in spores and dry seeds) The polarity of water molecules are caused by the angles that hydrogen atom bond to the oxygen atom (104.50), making the oxygen atom electronegative. This property accounts for the cohesiveness, the temperature-stabilizing capacity and the solvent properties of water.
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8	COHESION OF WATER Water molecules are cohesive(resist interuption) -- Hydrogen bonds form between the hydrogen atoms and the oxygen atoms of water molecules and are responsible for its high boiling point, high specific heat, and high heat of vaporization.
9	WATER TEMPERATURE Temperature stabilizing effects Temperature = measure of molecular motion Much energy required to break hydrogen bonds Water absorbs much heat before temperature increases
10	Water’s High Specific Heat Capacity Water has a high temperature-stabilizing capacity -- Specific heat is the amount of heat a substance absorb per gram to increase its temperature 10C. The specific heat of water is 1.0 calorie per gram.
11	Water’s High Heat of Vaporization Water has a high heat of vaporization, the amount of energy required to convert one gram of a liquid into vapor.
12	Water as a Solvent Water is an excellent solvent. A solvent is a fluid in which another substance, called the solute, can be dissolved. Hydrophobic: “water fearing” Hydrophilic: “water loving” When water is the solvent, the solution is call aqueous.
13	Properties of water originated from its polarity The solubilization of sodium chloride because water molecules form spheres of hydration
14	ACIDITY AND ALKALINITY Water molecules dissociate in the H⁺ and OH^-. Any chemical that donates more H⁺ is an acid. Those that produce OH^- are alkaline. The pH scale describe how acid or alkaline a solution is. The pH of the solution inside most living cells is close to 7, neutral.
15	BUFFERS Biological fluids contain ions that can accept or donate H⁺ and therefore resist any change in the pH of the solution.