Why Study Chemistry in Biology?

I. Atoms

Definition: smallest particle of an element

B. Composition

Subatomic Particle

Charge Mass Location

Proton +1 1 Nucleus

Neutron 0 1 Nucleus

Electron -1 1/1840 the mass of a

proton

Orbiting nucleus

C. If Neutral Atom: # protons = # electrons

II. ElementsA. Definition: substance that cannot be broken down into other substances

B. Biologically important elements i. Major: C H O N

ii. Minor: Ca Fe Mg I Se P K Na Cl

C. Symbol: usually from first letter or two of full name

Elements Con’t.

Atomic Mass 12.0107 amu

Mass Number

D. Atomic Number: # of protons in nucleus

ii. Atomic mass: count of the total number of protons and neutrons in an atom's nucleus

E. Atomic Mass / Mass Number

F. Isotopes

Mass Number

i. Definition: forms of the same element have same # of protons but different # of neutrons

ii. Radioactive isotopes: An isotope having an unstable nucleus that decomposes spontaneously

i. Molecules definition: two or more atoms held together by COVALENT bonds

G. Chemical Compounds

ii. Compound definition: a substance

containing two or more elements in a

fixed ratio– Ex: H2O, NaCl

Decoding Chemical Formulas??

C6H12O6

So in this molecule, there are 6 carbon atoms, 12 hydrogen, and 6 oxygen

Element subscript is the NUMBER of ATOMS

2H2O

• The number in front of H2O means

two entire molecules of H2O• Think of it like 2 x (H20)• Sooooo… how many total atoms of H are there?• Of oxygen?

• Atoms want to fill their outer energy

levels to be

• In order to do this, they will meet up with other atoms and either share or exchange electrons

• Atoms share electrons so that both atoms fill their outer energy level

A. Covalent Bonds

B. Ionic Bonds: gimme that electron!

• Atoms transfer electrons, becoming (+) or (-) charged

• This attraction brings them together– Ex: Na and Cl

i. Ions > An electrically charged atom

HydrogenHas 1 electron, needs 1 to fill its orbital

CarbonHas 4 electrons in outer level, needs 4 more to fill its orbital

Can form ONE bond

Can form FOUR bonds

IV. Water

A. Human Composition: 65–90% waterB. Plant Composition: 80-90%C. Formula: H2O

D. Bonds: i. Hydrogen bonds: the slightly (+) H atoms are attracted to nearby (-) O atoms, and develop a weak bond. ii. Covalent bonds: are shared between oxygen and hydrogen in a single molecule.

V. Water (con.’t)

5. Water is a polar molecule: i. Definition of polarity: molecule that has opposite electrical charges on opposite ends

ii. Why? Oxygen does not share electrons equally- pulls them closer to itself, making it more negative and Hydrogen more positive

V. Water (con.’t)

F. Unique molecule: i. Cohesion: 1. Definition: molecules of same kind stick to one another 2. Example: Surface tension; trees transporting water from roots to leaves

ii. Adhesion: 1. Definition: attraction that occurs between unlike molecules 2. Example: Water molecules and cotton string.

iii. Solutions: 1. Water is able to dissolve other polar and ionic compounds when mixed by causing the ions to break away and surround them.Ex.: Salt Water

2. Suspensions a. Definition: A heterogeneous mixture in which particles settle out of solvent-like phase some time after their introduction b. Example: oil & water

iv. Boiling Point: water will boil at 100C or 212F

G. Acids and Bases i. A water molecule can react to form ions ii. An ion is when a molecule breaks down and the atoms get a charge 1. Example: H+ and OH-

iii. pH Scale 1. How? Scale of 0-14; each pH unit represents a tenfold change in the concentration of H+ ions 2. Acid definition: pH 0-6 3. Base definition: pH 8-14

4. Buffer definition: substances that cause a solution to resist changes in pH.; works by accepting H+ ions when levels rise and donating H+ ions when levels fall, maintaining a constant pH a. Weak acid or base