8 24 12 Chapter 2 Molecules and Water Six elements 98 of all organisms Oxygen carbon hydrogen nitrogen calcium and phosphorous Trace elements iodine copper magnesium vitamins and minerals Atoms Protons Neutrons neutral Protons and neutrons make up almost the entire mass of an atom Electrons Atomic Number fixed number of protons in an atom Radioisotopes Superscript mass number Subscript atomic number Have a neutron added to the atomic structure to change the element One neutron added to Hydrogen changes it into Deuterium A neutron added to Deuterium changes it into Tritium Both Tritium and Carbon 14 are valuable research tools in biology Electrons and orbitals Electrons have a 1 charge Orbitals places where electrons are most likely found Each orbital contains a maximum of two electrons Electron shells First shell first orbital 1S contains 2 electrons Second shell four orbitals 2S Px Py Pz contains 8 electrons Px Py and Pz are dumb bell shaped The closer an orbital is to the nucleus the lower the energy of the electrons is in that orbital When electrons jump they require a quantam of energy Quantam of energy is absorbed by the electron that cases the jump from one energy level to another Quantam Leap Chemical Compounds 2 or more elements combined in a fixed ratio Chemical Formula H2O CO2 NaCl Structural Formula H O H O C O 8 24 12 Chemical Bonds Valence electrons Electrons of the outermost energy level The attractive force that holds two atoms together Covalent bond sharing of electrons H H H H Single bond one pair of electrons shared Double bond two pairs of electrons shared Triple bond three pairs of electrons shared Polar covalent bond Electronegativity in a bond is an atoms attraction for electrons Water molecule H O H polar Unequal sharing of electrons gives water its unique properties Polar solvent Ionic Bond an atom gains or loses electrons Cation Lost electrons Anion Gains electrons Na Cl Complete transfer of electrons NaCl Strong bond Water is polar and can be used to dissociate the NaCl molecule Hydrogen bonds Extremely important in biological systems H covalently bonds with an electronegative atom and the H becomes charged H can form a bond with another electronegative atom O and N Hydrogen bonding in water gives it its unique properties DNA H bonding is very important in DNA structure Attractions between the electron clouds of two molecules Weak interactions Van Der Waals forces Hydrophobic interactions Oxidation Reduction Occur between groups of non polar interactions Oxidation atom ion or molecule loses electrons Reduction atom ion or molecule gains reduction Redox reactions are always coupled Cytochromes in cell oxidation reduction reactions 8 24 12 It takes a large amount of heat input to raise the temperature of H2O one degree Celsius Water and its Properties 70 of our body is water 95 of a jellyfish is water Solvent properties Source of 02 that we breathe Cohesive Sticks together Adhesive Sticks to other molecules High surface tension High specific heat Most dense at 4 degrees Celsius Water cools ice is less dense than water and it floats High heat of vaporization Lots of energy to change water to steam Acids and Bases Acid proton donor H Anion HCl H Cl H ion contributes to the breakdown of food in the stomach Base proton acceptor Dissociate to a hydroxyl ion and a cation NaOH Na OH pH alkalinity or acidity of a solution 0 14 pH scale 0 6 acidic 7 neutral 8 14 basic Log 1 H 1M acidic solution 0 1M base solution 14 Neutrality 7 HCl 8 Chief cells in stomach Vinegar 3 pH 7 the concentration of OH and H are equal 8 24 12 Household ammonia 11 0 Buffer Body maintains a pH of 7 4 with the buffer system System that resists pH changes CO2 H2O H2CO3 H HCO3 bicarbonate ion CO2 buffer system also known as the bicarbonate buffer system Carbonic acid Resists pH changes Excess H H HCO3 H2CO3 Same situation occurs when one has excess hydroxyl ions Blood pH is approximately 7 4 Salts HCl NaOH NaCl H2O Electrolytes Non electrolyte Solution of alcohol sugars Salt acid or base solution that conducts electricity Fluid balance acid base balance nerve and muscle function blood clotting and bone formation