2. Life’s Chemical Basis

3.  Matter—anything that has mass and takes up space  Solid  Liquid  Gas

4.  Element—unit of matter than cannot be broken down further by ordinary chemical reactions  92 naturally occurring elements  98% of weight of any living thing is made up of 6 Carbon Hydrogen Oxygen Nitrogen Phosphorous Sulfur

5.  Atom—smallest indivisible unit of an element  Molecule—multiple atoms of the same element bonded together  Compound—multiple atoms of different elements bonded together

6.  Three subatomic particles  Protons  Neutrons  Electrons

10.  Orbit in “shells”  K Shell—2 electrons  L Shell—8 electrons  M Shell—18 electrons

11.  Atomic Number=Protons  Atomic Mass=Protons + Neutrons

12.  Elements in their natural state have neutral charge  Positive charge (protons) equals negative charge (electrons)

13.  Change in the number of neutrons  Does not affect charge  Carbon-14  Atomic Mass = 14 (6 Protons + 8 Neutrons)  Radioisotopes in medical diagnosis

14.  Change in the number of electrons  Affects charge  Anion—negative charge  More electrons than protons  Cation—positive charge  More protons than electrons

15.  Ionic  Covalent  Hydrogen

18.  Formed between ions  Electrons transfer from one atom to another  Opposite charges attract and hold atoms  Usually inorganic (acids, bases, salts, etc.)

19.  Atoms share electrons  Happens when both have room  Usually organic (proteins, carbohydrates, etc.)

21.  Bond between covalently bonded hydrogen atom & atom in different molecule or different location.  Individually weak, but collectively strong.

22.  Biologically important  Makes up 70-90% of living things  Unique properties

23.  Polar molecule (slight positive & negative charge)  Can easily dissolve other polar molecules  Hydrophilic  Hydrophobic  “universal solvent”  Cell membranes  Temperature stabilizing  Keeps cell processes from generating too much heat  Evaporation  Ice helps insulate

24.  “Stick together”  Adhesion—water sticks to itself  Cohesion—water sticks to other polar molecules  Due to polarity & hydrogen bonds

25.  pH scale  0-14  Based on H + & OH - molecules  Greater H +, lower the pH  Each unit is 10-fold change going from pH 6 to 5 increases H + by 10 times

26.  Acids  Donates H +  pH less than 7  Bases  Accepts H +  Releases OH -  pH greater than 7  Neutrals  Release equal numbers of H + and OH -  pH 7.0

27.  Buffers  Biological substances that help regulate pH  Release or absorb H + to keep pH unchanged  Ex.—Carbonic Acid, Bicarbonate regulate blood H 2 CO 3 + OH - HCO 3 - + H 2 0 HCO 3 - + H + H 2 CO 3