The Chemical Level of Organization Chapter 2

Chemistry Review  Matter – anything that occupies space and has weight  Atom – smallest stable unit of matter  Protons – positive electrical charge  Neutrons - uncharged  Electrons – negative electrical charge  Atomic Number  Number of protons in the nucleus  Atomic Weight (Mass)  Approx. number of protons + neutrons

Chemistry Review  Atom with a full outer electron shell is stable  helium, neon, argon, krypton, xenon, and radon  Atoms without full shell can achieve stability by sharing, gaining, or losing electrons through chemical reactions  Many of these reactions produce molecules  Molecules called compounds contain atoms of more than one element What are valence electrons

Chemistry Review  Element  Consists of entirely one type of atom  Many found in the body  Oxygen65%  Carbon18.6%  Hydrogen9.7%  Nitrogen3.2%  Calcium1.8%  Phosphorus1%  Potassium<1%  Chlorine, Magnesium, Sodium, Sulfur, Iron, Iodine  Compound  Molecules containing more than one type of atom  Water - H 2 O  Salt - NaCl  Methane - CH 4

Chemistry Review  Compounds have properties that can be very different from their components.  A mixture of hydrogen and oxygen is a flammable gas  Combining hydrogen and oxygen produces water  Bonding  Ionic Bonds  Covalent Bonds  Single  Double  Polar  Hydrogen Bonds

Ionic Bonding  Ions are charged atoms – having lost or gained electron(s)  Atoms are held together by the attraction between positive and negative charges

Ionic Bond - Sodium Chloride NaCl

Covalent Bonding  Atoms share electrons to complete outer electron shells  Resulting bond is called a covalent bond Ethane Hydrogen chloride

Single covalent bond  Sharing of one pair of electrons

Double Covalent Bond  Sharing of two pairs of electrons

Polar Covalent  An unequal sharing of electrons  In water:  The oxygen atom has a stronger attraction for the electrons – the electrons spend more time there – so there is a negative charge  The hydrogen side is positively charged

Hydrogen Bond  Within molecules some hydrogen atoms are positively charged and some are negatively charged  Hydrogen bonding does not form molecules but can alter shapes or pull molecules together

Acids Bases  A solute  Releases hydrogen ions  HCl H + + Cl -  A solute  Removes hydrogen ions  NaOH Na + + OH -  Hydroxide ions have an affinity for hydrogen ions  OH - + H + H 2 0

pH  pH is the concentration of hydrogen ions in a solution  pH range is 0-14, pure water is 7  Below 7 is acidic…hydrogen ions outnumber hydroxide ions  Above 7 is basic….hydroxide ions outnumbers hydrogen ions  In excessive amounts H + will disrupt cell and tissue function  Blood pH ranges from  Below 7 can produce a coma  Over 7.8 causes uncontrolled, sustained muscular contractions

Buffers  Compounds responsible for stabilizing pH  Remove or replace Hydrogen ions  Antacids  Alka-Seltzer, Rolaids, Tums  Tie up excess Hydrogen ions in the stomach  Extracellular - Sodium bicarbonate, ammonia  Intracellular – proteins, phosphate  H 2 O + CO 2 H 2 CO 3 H + + HCO 3 -  carbonic acid (H 2 CO 3 ) - bicarbonate (HCO 3 - )

Nutrients and Metabolites  Nutrients are essential elements and molecules absorbed from foods  Metabolites are all molecules synthesized or broken down by chemical reactions in our body  Nutrients and metabolites can be categorized as inorganic or organic

Inorganic Compounds  Generally do not contain carbon  Carbon Dioxide, Oxygen  Water  Inorganic Acids and Bases  Salts