1. Chemistry

2. ISOTOPES EVERY CHLORINE ATOM HAS 17 PROTONS, WITHOUT EXCEPTION,
HOWEVER, NOT EVERY CHLORINE ATOM HAS NEUTRONS.
ATOMS WITH THE SAME NUMBER OF PROTONS BUT CONTAIN DIFFERENT NUMBERS OF NEUTRONS ARE CALLED ISOTOPES.
BECAUSE ISOTOPES OF AN ELEMENT HAVE DIFFERENT NUMBERS OF NEUTRONS THEY HAVE DIFFERENT MASS NUMBERS.

3. ISOTOPES ARE CHEMICALLY ALIKE BECAUSE THEY HAVE IDENTICAL NUMBERS OF PROTONS AND ELECTRONS
IT’S THE ELECTRONS AND PROTONS THAT ARE RESPONSIBLE FOR CHEMICAL BEHAVIOR
BERYLLIUM
ISOTOPES
proton
neutron
electron

4. Cl Cl 18 20 EXAMPLE OF AN ISOTOPE 35 37 17 17 ATOMIC MASS NEUTRONS
ATOMIC NUMBER 18
NEUTRONS 20
NEUTRONS

5. IONS AN ELEMENT’S ATOMS ARE NOT ALWAYS NEUTRAL IN CHARGE.
WHEN AN ATOM LOSES OR GAINS ONE OR MORE OF ITS ELECTRONS IT BECOMES ION.
AN ION THAT HAS MORE ELECTRONS THAN PROTONS HAS A NEGATIVE ELECTRICAL CHARGE
AN ION THAT HAS FEWER ELECTRONS THAN PROTONS HAS A POSITIVE ELECTRICAL CHARGE
NOTE: IT’S THE PROTONS THAT DEFINE THE TYPE OF ATOM IT IS, BUT THE ELECTRONS DEFINE THE ATOM’S CHARGE.

6. SOME ATOMS GAIN ELECTRONS
ATOM’S IONIC CHARGE =
# PROTONS - # ELECTRONS - - - - - - - - - - - - - - - - - - O
O-2

7. The Nerve Cells
Sodium and potassium ions are used in the transmission of a nerve impulse.

8. Chemical Reactions Ø Chemical equations represent chemical reactions
Ø     Living things undergo thousands of chemical reactions
Ø     Chemical equations represent chemical reactions
Ø     CO2 + H goes to-----H2CO3 (carbonic acid) is a sample Chemical Reaction in living things
Ø     Reactants are on the left side of the equation, while products are on the right side  

9. Activation energy is required to start many reactions
Energy must be added to the reactants for most chemical reactions to occur; called activation energy

10. Enzymes
Enzymes are chemical substances in living things that act as catalysts & reduce the amount of activation energy needed
Organisms contain thousands of different enzymes
Most enzymes end with –ase (e.g. lipase is the enzyme that acts on lipids)

12. Physical Properties of Water
All of water’s UNIQUE properties are due to its POLARITY and HYDROGEN BONDING
POLARITY
H2O is a NEUTRAL molecule (p+ = e-)
Oxygen attracts most of the e- toward its end and away from the hydrogen
The OXYGEN END acts NEGATIVE, while the HYDROGEN END acts POSITIVE POLARITY (unequal distribution of charge)

13. HYDROGEN BONDING
Negative OXYGEN of ONE H2O molecule attracts the Positive HYDROGEN of ANOTHER H2O molecule

14. Bonding Strengths
True chemical bonds like covalent, ionic, and metallic bonds are the strongest bonds
Covalent bonds are the strongest force of attraction. They are stronger than ionic and metallic bonds.
Hydrogen Bonding is a weaker type of bonding because it’s between molecules.

15. Acids and Bases
The degree of acidity or alkalinity (basic) is important in organisms
The force of attraction between molecules is so strong that the oxygen atom of one molecule can actually remove the hydrogen from other water molecules; called Dissociation
H GOES TO----- H+  +  OH-
OH- called hydroxide ion; H+ called hydrogen ion

16. Free H+ ion can react with another water molecule to form H3O+ (hydronium ion)
Acidity or alkalinity is a measure of the relative amount of H+ and OH- ions dissolved in a solution
Neutral solutions have an equal number of H+ and OH- ions
Acids have more H3O+ ions than OH- ions; taste sour; and can be corrosive
Bases contain more OH- ions than H3O+ ions; taste bitter; & feel slippery  

17. PH Scale Compares the relative concentration of H3O+ ions and OH- ions
Scale ranges from 0 to 14; 0-3 is very acidic; 7 is neutral; is very basic or alkaline

18. Buffers Control of pH is important to organisms
Enzymes function only within a narrow pH range; usually neutral
Buffers neutral acids or bases in organisms to help control pH

19. Organic Molecules
Organic Compounds - have carbon bonded to other atoms (mostly Hydrogen) and determine structure/function of living things
Inorganic Compounds – all others
Organic compounds are made from a carbon skeleton which can
vary in length,
be branched or unbranched
have double bonds which vary in location
or may be arranged in rings.

20. Types of Organic Molecules
MACROMOLECULES fall into four major groups
1. Carbohydrates 2. Lipids 3. Proteins 4. Nucleic Acids