Chapter 2: The
Chemistry of
Life
ATOMS

Are the smallest particles of an
element that has all the properties of that
element

They are the building blocks of matter

They are made up of smaller particles:
protons, neutrons and electronsarranged in a specific way.
Atoms continued…

MOST STABLE (unlikely to react) when
outermost energy level is completely filled

Energy Levels- have a set maximum #
of electrons
Ion= atom that has lost or gained electrons
Lose electrons= become positive ions
Gain electrons= negative ions
Elements- a substance that cannot be
broken down by chemical processes into
simpler substances*Protons are
positively charged
*Neutrons have
no electrical
charge
*Electrons are
negatively
charged and are
located along the
outside
Isotopes
 Different
element
 They
number of neutrons, but same
have the same proton and electron
number!
Compound
two or more elements bonded
together
Ex. H2O, NaCl
Compounds that contain
CARBON and HYDROGEN
together are termed,
ORGANIC compounds
Chemical Bonds
Are
the attractions that hold 2
or more atoms together to form
a compound.
Whenever
a chemical bond is
formed or broken, energy is
either absorbed or released
Ionic Bonds
 the
chemical bond formed from the
attractive force between ions with
opposite charges = NO ELECTRICAL
CHARGE (electrons are lost by one
element & gained by another)
2. Covalent Bonds

bonds in which electrons are
NOT gained or lost, but shared.
 Co Ex.
cooperative (sharing)
Water, carbohydrates, lipids, proteins
and nucleic acids all have covalent bonds
TYPES of Covalent BONDS
SINGLE- 2 electrons shared
DOUBLE- 4 electrons shared
TRIPLE- 6 electrons shared
Types of bonds
The units formed by covalent bonds are called
molecules—most are made of atoms from different
elements
Some are not
Ex. N2, O2
Polar Molecules
 Atoms
do not share electrons equally
 There is a slightly negative end and a slightly
positive end
Ex. Water is POLAR
Van der Waals Forces
 Intermolecular
forces of attraction
 Weaker forces than ionic or covalent
bonds
 Gecko
 Do
example on page 39
section Assessment 2-1 #s 1-6
2-2 Properties of Water
 Solutions:
a uniform mixture of two or more
substances
 Water solutions are important because all
of life’s chemical processes occur in
solution


Uniform- mixed evenly so parts cannot be
distinguished
2 Components (parts)
 Solvent-
dissolving substance found in greatest
amount
 Solute- Dissolved substance
 Water
= The Universal Solvent
 Why? Because of polarity- dissolves polar
molecules, ionic compounds
2 Properties of water
 besides
having hydrogen bonds (which are
weak chemical attractions between hydrogen
and other atoms)

1. Cohesion- “sticking together”: causes surface
tension- a filmlike boundary forms on the surface
of water


Adhesion: attraction of molecules of different
substances
2. Expansion- water expands as it freezes
 Ice
has a lower density than liquid water
 Ice floats on water D= m/v D>1= sink
D<1= float
Acids, Bases and Salts
 When
ionic compounds are placed in water
forming a solution, the compound breaks
apart and releases ions.
 Acid- A compound that releases Hydrogen
Ions (H+) in water
 Base- A compound that produces Hydroxide
ions (OH-) when dissolved in water
 Salt- Compounds that yield ions other than
hydrogen or hydroxide ions when in solution,
are called salts
pH SCALE
 pH
scale is the standard measurement of
the concentration of hydrogen ions (H+)
present in a solution
 p= “power H= hydrogen ion
concentration
 pH scale ranges from 0 to 14
NEUTRAL
ACIDS
0
BASES
7
14
2- 3 Carbon Compounds
 Carbon
has 4 valence electrons. Can
bind with many elements and to each
other. Organic Chemistry is the study of
carbon and hydrogen compounds.
 Most abundant elements in our body :
Don’t CHNO: carbon, Hydrogen, nitrogen
and oxygen
 Macromolecules: large molecules are
formed by a process called
polymeriazation
 Monomers + monomers + monomers=
polymers
 Four
groups of organic compounds
found in living things:
 1.
Carbohydrates: sugars starches and
cellulose—living things use carbs as main
energy source and structural purposes
Sugars: mono, di and polysaccacharide

Animals use glycogen

Plants use starch
 2.
lipids: fats, oils and waxes—Can be
used to store energy, they are
important parts of membranes and
waterproof coverings.
3.
nucleic acids: store and transmit
hereditary or genetic information--made of monomers called nucleotides

3 PARTS!!
2 Kinds
DNA
Deoxyribonucleic
acid
RNA: ribonucleic
acid
4. Proteins: made up of smaller units
called amino acids (Amino because
has an NH2 on one end and a –COOH
on the other)
Very important: Protein Synthesis in cells
Functions: Defense(antibodies),
movement(actin/myosin), Transport
(hemoglobin), hair and nails (keratin)
2-4 Chemical Reactions and
Enzymes
 Chemical
Reactions: a process that
changes one set of chemicals into
another set of chemicals


They always involve the breaking of bond in
the reactants and the formation of new
bonds in the products
Example ( Label the reactants and products)
 CO2
+ H2 O
H2CO3
Energy in Reactions
 Energy
is released or absorbed whenever
chemical bonds form or are broken
 Chemical
reactions that release energy
often occur spontaneously.
Chemical reactions that absorb energy
will not occur without a source of energy.
 Energy
Releasing
2H2 + O2
2H2O
Energy Absorbing
2H2O
2H2 + O2
Energy Releasing (Exothermic)
Activation
Energy- the
energy needed to
get a reaction
started
Energy Absorbing
(Endothermic)
 Catalyst:
is a substance that speeds up
the rate of a chemical reaction- they
work by LOWERING the activation energy
 ENZYMES
are protein catalysts
Enzyme - Substrate Complex
 Substrate=
reactant, substance to be
changed
 Active site= where the substrate attaches