Chapter 2: The Chemical Basis of Life
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Matter is anything that has
mass & takes up space.
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Solid
Liquid
Gas
Elements make up all
matter (living and
nonliving).
EX. Carbon, oxygen,
hydrogen
Basic Chemistry
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There are only 25 elements
that are basic to life.
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CHON= Make up 96% human weight
(carbon, hydrogen, nitrogen,
oxygen)
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The atom is the smallest part
of an element.
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Made up of:
1) protons (+ charge)
2) neutrons (neutral)
3) electrons (- charge)
Basic Chemistry cont.
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Atomic Number:
the number of protons in the
nucleus of atom that makes it
unique.
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Atomic Mass = # of protons +
# of neutrons
Basic Chemistry cont.
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Isotopes = same # protons,
different # of neutrons
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Radioactive isotopes release energy in the
forms of rays & subatomic particles.
 Can harm cells
 Damage DNA
 Cause cancer
May have beneficial uses:
 Sterilize medical equipment
 Kill cancer cells
Chemistry of Life
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Bonds:
 Ionic: oppositely charged ions are attracted to each other after gaining or
losing electrons
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Covalent: atoms share valence electrons
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Water soluble (ionic bonds break)
Ex. NaCl table salt
Bonds do not break in water; often not water soluble
Ex. C6H12O6 glucose
Polar covalent: atoms share valence electrons unequally
 A prerequisite for hydrogen bonds
Hydrogen: partially positive H (part of a polar covalent bond) is
weakly attracted to partially negative O, N, or F (part
of polar covalent bond)
 Ex. H20 water
Water’s Life Supporting Properties

Water is cohesive & adhesive

Cohesion: water molecules stick together
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Hydrogen has partial positive charge
Oxygen has partial negative charge
Oxygen of one H2O molecule attracted to Hydrogen of another
molecule

Adhesion: water is attracted to other partially charged
substances
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Surface Tension: a measure of how difficult it is to stretch or
break the surface of a liquid
Water’s Life Supporting Properties

Heat: the amount of energy associated with the
movement of atoms and molecules

Temperature: measures average speed of molecules

Ice is less dense than liquid water due to the 3-D
crystalline bonding pattern
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Hydrogen bonds are stable
Atoms are equally spaced apart
Hydrogen bonds in liquid water constantly break & re-form
Water’s Life Supporting Properties

Solution: liquid consisting of a
uniform mixture of 2 or more
substances

Solvent: dissolving agent
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Solute: Substance that is
dissolved

Aqueous solution: water is the
solvent

Water can dissolve ionic
compounds & other polar
molecules (Ex. NaCl, sugar)
Chemistry of Life

pH (Power of Hydrogen ions)
 Scale from 1 (highest # of
H+) to 14 (lowest # of H+)
 Low numbers are acids (16)
 High numbers are bases (814)
 7 is neutral
Chemistry of Life
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All living things contain carbon.
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Organic compounds are substances that contain carbon and make
up all living things.
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There are four kinds of organic compounds:
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1) carbohydrates
2) lipids
3) proteins
4) nucleic acids
Organic Compounds
Carbohydrates
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Sugars & starches
Contain elements C, H, O in a 1:2:1 ratio
C6H12O6 glucose
Energy source for living things

The building blocks of carbohydrates are monosaccharides or single sugars.
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Dissacharides are two single sugars bonded together.
Ex. Sucrose (table sugar)= glucose + fructose
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Polysaccharides are 3 or more single sugars bonded together.
Ex. Starch, cellulose, glycogen
Organic Compounds
Lipids
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Fats, waxes, and oils
Do not dissolve in water
Made up of C, H, and O but
not in a ratio
Store and release energy
Ex. Steroids, phospholipids,
chlorophyll
The building blocks
of lipids are fatty
acids.
Organic Compounds
Proteins
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Made up of the elements C, H, O, N, S
Make up hair, skin, nails
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The building blocks of proteins are amino acids.
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Enzymes are special proteins that speed up chemical reactions.
Ex. Salivary amylase
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Organic Compounds
Nucleic acids
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Ex. DNA & RNA
DNA is found in the nucleus of all
living cells.
DNA makes up genes which store
hereditary information.
The building blocks of
nucleic acids are
nucleotides.
Nucleotides are made up of 3 parts:
1) a base
2) a sugar
3) a phosphate
ATP
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Adenosine triphosphate (ATP) is an energy found
in living cells.
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Fuel for cells
Used to make proteins & carbohydrates in cell
Energy needed for muscle cells to contract
Energy needed for nerve cells to conduct impulses

ATP stores its energy in the chemical bonds
between the phosphate atoms.

Energy is released when bonds
are broken.
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ATP is made up of a sugar, the
base adenine, and 3 phosphate
molecules.