Life’s Chemical Basis
 Matter—anything
space



Solid
Liquid
Gas
that has mass and takes up
 Element—unit
of matter than cannot be
broken down further by ordinary chemical
reactions


92 naturally occurring elements
98% of weight of any living thing is made up of 6

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Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorous
Sulfur
 Atom—smallest
indivisible unit of an element
 Molecule—multiple atoms of the same
element bonded together
 Compound—multiple atoms of different
elements bonded together
 Three



subatomic particles
Protons
Neutrons
Electrons
Orbit in “shells”
 K Shell—2 electrons
 L Shell—8 electrons
 M Shell—18 electrons

 Atomic
Number=Protons
 Atomic Mass=Protons + Neutrons
 Elements
in their natural state have neutral
charge

Positive charge (protons) equals negative charge
(electrons)
 Change
in the number of neutrons
 Does not affect charge
 Carbon-14

Atomic Mass = 14 (6 Protons + 8 Neutrons)
 Radioisotopes
in medical diagnosis
 Change
in the number of electrons
 Affects charge
 Anion—negative

More electrons than protons
 Cation—positive

charge
charge
More protons than electrons
 Ionic
 Covalent
 Hydrogen
Formed between ions
 Electrons transfer from one atom to another
 Opposite charges attract and hold atoms
 Usually inorganic (acids, bases, salts, etc.)

Atoms share electrons
 Happens when both have room
 Usually organic (proteins, carbohydrates, etc.)

 Bond
between covalently bonded hydrogen
atom & atom in different molecule or
different location.
 Individually weak, but collectively strong.
 Biologically
important
 Makes up 70-90% of living things
 Unique properties
 Polar
molecule (slight positive & negative
charge)

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
Can easily dissolve other polar molecules
Hydrophilic
Hydrophobic
“universal solvent”
Cell membranes
 Temperature

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
stabilizing
Keeps cell processes from generating too much
heat
Evaporation
Ice helps insulate
 “Stick



together”
Adhesion—water sticks to itself
Cohesion—water sticks to other polar molecules
Due to polarity & hydrogen bonds
 pH

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
scale
0-14
Based on H+ & OH- molecules
Greater H+, lower the pH
Each unit is 10-fold change

going from pH 6 to 5 increases H+ by 10 times
 Acids


Donates H+
pH less than 7
 Bases



Accepts H+
Releases OHpH greater than 7
 Neutrals

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Release equal numbers of H+ and OHpH 7.0
 Buffers

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Biological substances that help regulate pH
Release or absorb H+ to keep pH unchanged
Ex.—Carbonic Acid, Bicarbonate regulate blood
H2CO3 + OH-
HCO3- + H20
HCO3- + H+
H2CO3