The Chemistry of Life
2.1 Introduction to Chemistry
2.1 Introduction to Chemistry
 elements - make up earth &
organisms (O, C, H, N,
S, P, K, Si, Al, Fe, Ca)
cannot be broken down by
a chemical process into a
simpler substance
2.1 Introduction to Chemistry
Compounds - combinations of
elements (ex. Hemoglobin
(compound) contains Fe (element)
Organic compounds - all contain
carbon -ex. Carbohydrates,
lipids, proteins, nucleic
acids
2.1 Introduction to Chemistry
inorganic compounds - do not
contain carbon
(ex. Table salt = NaCl)
C6H12O6 – 24 total atoms

6 carbon atoms
 12 hydrogen atoms
 6 oxygen atoms

How many atoms are in this molecule?
C55H72MgN4O5
137
2.1 Introduction to Chemistry
 Atoms - smallest particle of an
element that has the elements
properties
 protons (+) = Atomic number
 neutrons (no charge)
 Protons and neutrons together
make up the nucleus
 electrons (-) – used to form bonds
with other elements
2.1 Introduction to Chemistry
 Changes in the number of electrons causes
atoms to become + or –
 Outer most energy level (orbit) likes to be full
– more stable that way
 Atoms will give up, gain, or share electrons to
fill the outer orbit
 1st level – 2 electrons
 2nd level – 8 electrons
 3rd level – 8 or 18 electrons
2.1 Introduction to Chemistry
 Sodium – 11 protons and 11 electrons



2 electrons in the 1st level
8 electrons in the 2nd
1 electron in the 3rd
2.1 Introduction to Chemistry




Chlorine – 17 protons, 17 electrons
2 electrons in the 1st level
8 electrons in the 2nd level
7 electrons in the 3rd level
 Sodium wants to give up the last electron
whereas Chlorine wants to gain an electron to
fill the 3rd level with 8 electrons
 Atoms bond with other atoms to become
more stable
2.1 Introduction to Chemistry
21. Introduction to Chemistry
IONIC BOND
2.1 Introduction to Chemistry
 Ions - atoms that gain or lose
an electron and have a
charge
2.1 Introduction to Chemistry
 Chemical Bond -The force that
holds atoms together
When a chemical bond is
broken, energy is absorbed
or released
IONIC BONDING
Electrons are lost by one
element and gained by
another
Outer energy level in both
elements is full (stable)
2.1 Introduction to Chemistry
2.1 Introduction to Chemistry
 Ionic bond- a bond b/w oppositely
charged molecules
One element loses e- &
the other element gains e Covalent bond – a bond where electrons are
shared (carbs, lipids, proteins
& nuc. Acids); three types:
single, double, triple
COVALENT BONDING
Electrons shared in a chemical
bond (each atom donates one
electron)
Outer energy level in both elements
is full (stable)
Double covalent bonds have four
electrons
Triple covalent bonds have six
electrons
COVALENT BOND
2.1 Introduction to Chemistry
 Polar Covalent – bond w/ unequal
sharing of electrons that
results in slightly positive
& slightly negative ends
Water – example of covalent
POLAR COVALENT
NONPOLAR COVALENT
COVALENT VS. IONIC
2.1 Introduction to Chemistry
 Hydrogen Bonds – bonds that hold
molecules together rather
than atoms
These bonds are weaker
than ionic or covalent
bonds
* like in water – hydrogen bonds are the
force that holds water molecules
together
2.1 Introduction to Chemistry
2.1 Introduction to Chemistry
 Isotopes - atoms of the same
element that have a
different number of neutrons
2.1 Introduction to Chemistry
Isotopes - have an unstable
nucleus that breaks
apart giving off energy in
the form of radiation
 used to tell age of fossils
 preserve food
 treat cancer
2.1 Introduction to Chemistry
2.2 Introduction to Chemistry
 Water is found in all living organisms
 Water is a polar molecule
 Being polar allows water to dissolve ionically
bonded compounds easily
 When compounds dissolve in water they form
a solution
 Living things are composed of 70-90% water
2.2 Introduction to Chemistry
2.2 Introduction to Chemistry
 Solutions --Water is known as
the universal solvent

Chemical properties of water are
important b/c they allow it to form
solutions (aka. Uniform mixtures)
2.2 Introduction to Chemistry
Solute --That which is being
dissolved (sugar)
 Solvent --That which does the
dissolving (water)
2.2 Introduction to Chemistry
Ionic Compounds --dissolve
readily in water b/c
water is polar
Polar covalent compounds -dissolve in water
2.2 Introduction to Chemistry

Cohesion – “sticking together” b/c of
hydrogen bonding
surface tension – Like a water
strider walking on water
Plants --have a xylem (straw-like
tubes that carry water)
where the water is pulled
up!
2.2 Introduction to Chemistry
 Expansion – water expands when it
freezes, which is opposite to
most substances
 results in ice having a lower density
than liquid water so the ice floats
2.2 Introduction to Chemistry
-ponds “freeze on top” so
organisms are able to
live underneath
-Problem for roads
2.2 Introduction to Chemistry
 Acids & Bases --Formed by ionic
compounds in solution
Acids – release Hydrogen ions (H+)
in water

(ex. HCl in stomach acid)
2.2 Introduction to Chemistry
Bases – Produce hydroxide (OH-)
ions in solution
 (ex. NaOH in soap & egg whites)
Salts – yield other ions
 (ex. NaCl and KCl)
 When salt is dissolved in water;
sodium & chlorine “disassociate”
or temporarily separate
2.2 Introduction to Chemistry
 pH --“power of H+”
-pH scale measures the
concentration of Hydrogen
ions
Scale 0-14
acid: 0 to < 7
bases: > 7 to 14
2.2 Introduction to Chemistry
Blood - 7.4 (lethal if more acidic
than 7 and more basic than 7.8)
Stomach acid - 2
A change in pH --in your body
results in halting some enzyme
functions
2.2 Introduction to Chemistry
Acid rain --contains sulfuric acid and nitric
acid
Acid rain pH < 5.6
Acid rain washes away vital
minerals from soil, kills aquatic
organisms & strip nutrients from
plants
2. 3 The Compounds of Life (most
contain carbon)
 Carbohydrates - store energy &
provide shape
(composed of C,H&O)
 Starch - plants stored energy
that is made of sugars
(monosaccharides,
disaccharides &
polysaccharides)
CARBON
 Carbon is important biological element
because it can form four bonds with other
elements and long chains or rings
 Polymer – large molecule made up of many
smaller units like starch
 Monomer – unit that makes up polymer;
glucose is the monomer for starch
2. 3 The Compounds of Life
 Glycogen - animals stored
energy made from
sugars (same
saccharides)
Cellulose - simple sugars that
make structural
carbos in plants
GLUCOSE
 Monomer of starch, glycogen, and cellulose
2. 3 The Compounds of Life
 Lipids - long term energy
storage; four types; not
soluble in water
Fats - provide insulation
Wax - repel water
Phospholipids - give
structure to cell
membranes
2. 3 – The Compounds of Life
 Steroids - cholesterol in cell
membranes
2. 3 The Compounds of Life
 Proteins - large, complex
molecules composed of
many smaller molecules
called amino acids (only
20 amino acids make different
combinations & proteins)
 Amino acids are held together by
peptide bonds to form proteins
2. 3 The Compounds of Life
Proteins - make enzymes that
help control chemical
reactions (ex. Speed up
digestion, releasing
energy during cellular
respiration, building up
proteins
2.3 The Compounds of Life
1. Defense
4. Regulation
2. Movement
5. Transport
3. Structure
6. nutrition
2. 3 The Compounds of Life
Nucleic Acids - large, complex
molecules that contain
hereditary or genetic
info – two types
 monomer – nucleotide (made
up of nitrogen base, phosphate,
and sugar)
2. 3 The Compounds of Life
DNA - carries instruction that
control
activities of cell
(blueprint)
2. 3 The Compounds of Life
 RNA - make the proteins
(builder)
2.4 Chemical Reactions and Enzymes
Chemical Reaction – creation of
new substances by
breaking or forming chem.
bonds
Carbs broken for energy
All chemical reactions involve
energy (absorbed or released)
2.4 Chemical Reactions and Enzymes
 2H2 + O2 2H2O
 _C6H12O6 + __ O2 __C02 + __
H2O
2.4 Chemical Reactions and Enzymes
 Reactions happen in living &
nonliving things all the
time
 can be sped up by increasing temp or by
involving a catalyst
 Catalyst - in organisms are called
enzymes (see sucrose
example, fig. 2.15)
 Enzymes - break bonds others help
form bonds
2.4 Chemical Reactions and
Enzymes
*Type of protein
*Act as a catalyst, speeding up
chemical reactions
1. Substrate- substance being
changed by enzyme
2. Active site- region on enzyme
where substrate attaches
(this is the enzyme substrate
complex)
2.4 Chemical Reactions and Enzymes
3. Substrate is altered (bond
weakened) so that bond is
broken
4. Products released and
enzyme is unchanged (only
the substrate changes)
5. Enzyme is free to bond with
another substrate
2.4 Chemical Reactions and
Enzymes
*Enzymes work by either breaking or forming
compounds
*Enzymes work only within specific ranges of
temperature and pH.
*Enzymes catalyze specific reactions- only specific
substrates will fit into the active site
*Enzyme affected by high
temperature
*Enzymes are also affected by the concentration
of the substrate and the enzyme
Application: bee sting home remedymeat tenderizer (enzyme) on bee
sting (protein in venom)