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Chemistry of Life
Chemistry is the study of how matter
interacts, thus we need to understand some
of the basic rules and ideas about matter to
understand how living things work.
Vocabulary
Element - substance that cannot be separated into
simpler substances by chemical means.
92 occur naturally
13 made by humans
Compound - combination of two or more elements
Life Elements
Typical living thing composed (99.9% wt)
of six elements:
C, H, N, O, P, and S.
Seventeen other elements occur in minute
quantities or as traces.
Vocabulary
Atoms - smallest particle into which an element can be
divided and still have the properties of that element.
Molecule - two or more atoms joined together by
molecular bonds.
Atom Organization
Sub-atomic
particle
charge
Wt. (amu)
location
proton
+
1
Nucleus
neutron
none
1
Nucleus
electron
-
0
Orbit
nucleus
Formulas
Atomic Number = # protons
Note: "normal" atom the number of electrons =
number of protons (atom has no net charge)
Atomic Wt (Mass) = # protons + # neutrons
Atomic Variants
1. Isotopes - differ in the number of neutrons
in the nucleus, thus changing wt. of
element.
2. Ions - number of electrons differs from the
number of protons, thus giving element net
negative or a net positive.
Electrons In Orbit

Number electrons in outer-most energy
level gives each atom its unique chemical
behavior.

(E.g) H is an odorless gas; C is a black
powdery substance.
Electrons In Orbit
* Maximum number electrons / orbital determined
by the formula
X = 2N2
(where X = maximum number of electrons
in energy level number N).
ATOMIC STRUCTURE
MOLECULAR BONDS:
two or more atoms bonded
together by energy links
Types of Molecular Bonds
Covalent Bonds• Most common type
• occurs when two or more atoms share pair elec.
• may form single, double, or triple bonds
1. POLAR COVALENT = un-equal sharing of elec
2. NON-POLAR COVALENT = elec pair equally
shared
2. Hydrogen Bond

bond between the negative pole of a polar
molecule and the slight positive charge on
a hydrogen atom that is participating in
another polar molecule.

weakest
3. Ionic Bonds

a complete transfer of electrons from one
molecule to another. It is most common
when one molecule needs just one or two
to complete its outermost shell and the
other has only one or two in its outermost
shell.
Properties of Water
1. High Specific Heat - takes 1 calorie (a unit of heat
energy) to raise the temperature of one gram of water
1o Centigrade.
* keeps environment of cells constant
2. High Heat of Vaporization - takes 540 calories of
heat to change 1 gram of liquid water at 100o C to 1
gram of water vapor at 100o C
* sweating can help to cool organisms
Properties of Water
3. High degree Cohesion + Adhesion = capillary action
* plants use this to draw water against gravity
4. High Surface Tension - tendency of molecules at the
surface of a liquid to cohere to each other and not to the
air above.
* some insects use this to walk on water!
5. Ice floats - Ice is less dense than liquid water and hence
floats (WHY??)
* allows fish and other organisms to survive winter
Properties of Water
6. Universal Solvent - dissolves ionic & most polar substances
* excellent medium for cytoplasm!
Solvent = that which dissolves another
Solute = that which is dissolved
Solution = solvent + solute
Hydrophilic ("water-loving") substances readily dissolve in water
while hydrophobic ("water-fearing") substances do not dissolve
in water.
Properties of Water
7. Water Dissociation- slight tendency to fall apart (dissociate)
into hydrogen ions (H+) and hydroxide ions (OH-).
An Acid is a substance that gives off hydrogen ions when dissolved
in water.
A Base is a substance that accepts hydrogen ions
(thereby increasing the hydroxide ions).
PH Scale : 0_______________7___________________14
Acids
Neutral
Bases
Highest H+ conc.
Lowest H+ conc.
4 Classes of Organic Molecules
1.
2.
3.
4.
Proteins
Carbohydrates
Lipids
Nucleic Acids
Functions of Proteins
1. Structural proteins - form cell parts
2. Regulatory proteins - control cell processes
3. Enzymes - facilitate (help) many chemical reactions; they
do this by lowering the amount of energy needed
to start the reaction; the enzyme is not
permanently altered in the process.
4. Hormones - chemical messengers
5. Transport proteins - carry other substances around cells
or from cell to cell.
Carbohydrates
• Most abundant types organic molecules
• Function: energy sources & structural components
• monomers of carbohydrates = isomers of C6H12O6
3 Major Categories
Carbohydrates
1.
2.
3.
Monosaccharides
Disaccharides
Polysaccharides
Lipids
Fats,
oils, waxes, steroids, & phospholipids.
Function: energy storage, waterproof
coatings, chemical messengers.
Three categories of lipids:
Triglycerides
(saturated & unsaturated fats)
Waxes
Phospholipids
Steroids
Nucleic Acids
Nucleic Acids - Large molecules
carry
coded genetic information
Polymers of nucleotides (monomer)
Two main types:
Deoxyribonucleic

Double helix of anti-parallel nucleotide chains
Ribonucleic

acid (DNA)
acid (RNA)
Single nucleotide chain