The Chemistry of Life
Objectives
 What three subatomic particles make up atoms?
 How are all the isotopes of an element similar?
 What are the two types of chemical bonds?
The Big Idea
Life Depends on chemistry
Chemical reactions keep you
alive
Atom
Basic unit of matter
Democritus Atomic Theory
The theory states that these
atoms are all individually
created and cannot be
separated, no matter what
scientific procedures are
applied.
Subatomic
particles
 Protons Positively charged (+)
 Neutrons  Electrons -
Electrons
Not charged (neutral)
Negatively charged (-)
Bind together
to form the
nucleus
Protons
Nucleus
Neutrons
Element
A pure substance that consists
of just one type of atom
An elements Atomic Number = number
of protons
Atomic number
6
C
Carbon
12.011
Isotope
Atoms of the same element that
differ in the number of neutrons
they contain
Nonradioactive carbon-12
6 electrons
6 protons
6 neutrons
Nonradioactive carbon-13
6 electrons
6 protons
7 neutrons
Radioactive carbon-14
6 electrons
6 protons
8 neutrons
The Sum of protons and neutrons in the nucleus of an
atom is its MASS NUMBER
6
C
Carbon
12.011
Mass number
The weighted average of the masses
of an elements isotope is called its
atomic mass
Radioactive isotopes
Can be dangerous
Can be used
practically
 Radioactive dating
 Treat cancer
 Kill bacteria
Compounds
A substance formed by the
chemical combination of two or
more elements in definite
proportions
Ex) H2O, NaCl
Sodium – silver colored metal, soft enough to cut with a knife
Sodium reacting explosively in water
Chlorine – poisonous green
gas used to kill many people
in WWII
Combination of
sodium and
chlorine
Table Salt
Yellow Boxes = Top 5 Elements present in the human body
Green Boxes = Second 5 Top Elements present in the human body
Blue Boxes
= Trace elements that are required by the human body
Violet Boxes = Elements that are deleterious to the human body.
The following periodic chart summarizes the elements of the periodic table, in terms of
human composition, and human toxicity. The lesser elements are often referred to as
minerals, when referring to human nutrition and health.
Several minerals are required by the human body for proper nutrition. Food supplements
may be required to ensure that you are receiving all the nutritional minerals that you
need. Major liquid mineral supplements which may be required are calcium supplements,
phosphorus supplements, and potassium supplements. Trace mineral supplements often
include magnesium supplements, iron supplements, zinc supplements, and selenium
supplements.
Ionic Bonds
Formed when one or more
electrons are transferred from
one atom to another
Sodium atom (Na)
Chlorine atom (Cl)
Sodium ion (Na+)
Chloride ion (Cl-)
Protons +11
Electrons -10
Charge
+1
Protons +17
Electrons -18
Charge
-1
Transfer
of electron
Protons +11
Electrons -11
Charge
0
Protons +17
Electrons -17
Charge
0
If an atom loses an electron it
becomes positive
If an atom gains an electron it
becomes negative
Ions
Positively and negatively
charged atoms
Covalent Bonds
Forms when electrons are
shared between atoms
Molecule
The structure that results when
atoms are joined together by a
covalent bond
Smallest unit of most compounds
Van der Waals Forces
A slight attraction that develops
between the oppositely charged
regions of nearby molecules due
to unequal sharing of electrons
1. Describe the structure of an atom.
Atoms are made up of protons and
neutrons in a nucleus. Electrons are in
constant motion in the space around
the nucleus.
2. Why do all isotopes of an element
have the same chemical properties
They have the same number of
electrons
3. What is a covalent bond?
A bond formed when electrons are
shared between atoms
4. What is a compound? How are they
related to molecules
A compound is a substance formed by
the chemical combination of two or
more elements in definite proportions.
A molecule is the smallest unit of most
compounds
5. How do Van der Waals forces
hold molecules together?
When the sharing of electrons
are unequal, a molecule has
regions that are charged. An
attraction can occur between
oppositely charged regions of
nearby molecules
6. How are ionic bonds and Van
der Waals forces similar? How
are they different?
In both cases, particles are held
together by attractions between
opposite charges. The difference
is that ionic charges are stronger
Objectives
Why are water molecules polar?
What are acidic solutions? What
are basic solutions?
The Big Idea
Much of our planet is covered in
water
Water is necessary for life to exist
If life exists on other planets, there
most likely is water present
Water has many properties that
make life possible
Polarity
(-)
The oxygen atom has
a stronger attraction for
electrons
(+)
Hydrogen Bonds
 Because of waters partial charges, they
can attract each other and create
hydrogen bonds
 Not as strong as covalent or ionic
bonds
 Waters ability to create multiple
hydrogen bonds gives it many special
properties
Cohesion
Attraction between molecules of
the same substance
Adhesion
Attraction molecules of different
substances
Mixture
Material composed of two or more
elements or compounds that are
physically mixed but not
chemically combined
Ex.) salt & pepper, earths
atmosphere
Solutions
Mixture of two or more substances
in which the molecules are evenly
distributed
Ex.) salt water
Settles out over time
Solutions
Cl-
Cl-
Na+
Na+
Water
Water
Solute
Substance that is dissolved
Ex.) salt
Solvent
The substance that does the
dissolving
Ex.) Water
Suspensions
Mixture of water and non-dissolved
materials
Ex.) sugar solution, blood
Separate into pieces so small, they
never settle out
The pH scale
Indicated the concentration of
hydrogen ions in a solution
Acid
Neutral
Base
Acids
Any compound that forms H+
(hydrogen) ions in solution
Base
A compound that produces OH-
(hydroxide) ions in solution
Buffers
Weak acids or bases that can react
with strong acids or bases to
prevent sharp, sudden pH changes
1. Use the structure of a water
molecule to explain why its polar
Oxygen atom has greater
attraction for electrons, therefore
the oxygen atom is negative and
the hydrogen end is positive
2. Compare acidic and basic
solutions in terms of their H+ ion
and OH- ion concentrations
Acid have more H+ ions than OHions, and bases have more OH- ions
than H+ ions
3. What is the difference between a
solution and a suspension?
In a solution, all components are
evenly distributed. In a suspension,
un-dissolved particles are
suspended
4. What does pH measure?
The concentration of H+ ions in a
solution
5. The strong acid hydrogen floride
(HF) can be dissolved in pure
water. Will the pH of the solution
be greater or less than 7?
less than 7
Objective
What are the functions of each
group of organic compounds?
Section 2-3
Life’s backbone
 Most of the compounds that make up living things
contain carbon. In fact, carbon makes up the basic
structure, or “backbone,” of these compounds. Each
atom of carbon has four electrons in its outer energy
level, which makes it possible for each carbon atom
to form four bonds with other atoms.
 As a result, carbon atoms can form long chains. A
huge number of different carbon compounds exist.
Each compound has a different structure. For
example, carbon chains can be straight or
branching. Also, other kinds of atoms can be
attached to the carbon chain.
Methane
Acetylene
Butadiene
Benzene
Isooctane
Macromolecules “giant molecules”
Formed by a process called
polymerization
Monomers
Smaller units
Polymers
Linked up monomers
Carbohydrates
Compounds made up of carbon,
hydrogen, and oxygen atoms
usually in a ratio of 1:2:1
Main source of energy
The monomers of starch are sugars
Single sugar molecules are called
monosaccharides
The large macromolecules formed
from monosaccharides are known
as polysaccharides
Starch
Glucose
Lipids
Made mostly from carbon and
hydrogen atoms
Used to store energy
Lipid
Fatty Acids
Glycerol
Proteins
Macromolecules that contain
nitrogen as well as carbon,
hydrogen, and oxygen
Proteins are polymers of molecules
called amino acids
Amino Acids
Carboxyl group
General structure
Alanine
Serine
More than 20 different amino
acids, can join to any other amino
acid
The instructions for arranging
amino acids into many different
proteins are stored in DNA
Each protein has a specific role
The shape of proteins can be very
important
Proteins
Amino
Acids
Nucleic Acids
 Macromolecules containing hydrogen,
oxygen, nitrogen, carbon, and phosphorus
Double
Helix
Nucleotides
 Consists of 3 parts: 5-carbon sugar,
phosphate group and nitrogen base
Nitrogen Base
Phosphate
group
5-Carbon Sugar
2 kinds of nucleic acids
RNA (ribonucleic acids) – contains
sugar ribose
DNA (deoxyribonucleic acid) –
contains sugar deoxyribose
1.
Name four groups of organic compounds found in
living things
carbohydrate, lipid, protein, nucleic acids
2. Describe at least one function of each group of organic
compounds
carbohydrates – energy
lipids – store energy
proteins – form tissue
nucleic acids – transmit hereditary information
3. Compare the structures and
functions of lipids and starches
Lipids are made from carbon and
hydrogen. Starches are made of
carbon, hydrogen and oxygen. They
both can be used to store energy
Objectives
What happens to chemical bonds
during chemical reactions?
How do energy changes affect
whether a chemical reaction will
occur?
Why are enzymes important to
living things?
The Big Idea
Living things are made up of
chemical compounds
Everything that happens to an
organism is based on chemical
reactions
Chemical Reactions
A process that changes or
transforms one set of chemicals
into another.
Reactants
Elements or compounds that enter
into a reaction.
Products
Elements or compounds produced
by a chemical reaction.
Example Reaction: Getting rid of
Carbon Dioxide
In the blood
CO2 + H20  H2CO3 (carbonic acid)
In the lungs
H2CO3  CO2 + H2O
Released as you
breathe
Energy in reactions
Energy-Absorbing Reaction
Energy-Releasing Reaction
Activation
energy
Products
Activation energy
Reactants
Reactants
Products
Activation Energy
The energy that is needed to get a
reaction started
Enzymes
Some chemical reactions are too
slow or have activation energies
that are too high to make them
practical for living tissue.
These chemical reactions are made
possible by CATALYSTS.
Catalyst
Substance that speeds up the rate
of chemical reactions
Work by lowering a reactions
activation energy
Enzyme
BIOLOGICAL CATALYSTS
Speed up reactions in cells
Very specific
Named for the reaction it catylzes
Enzyme names always end in -ase
Reaction pathway
without enzyme
Activation energy
without enzyme
Reactants
Reaction pathway
with enzyme
Activation
energy
with enzyme
Products
Substrates
The reactants of enzyme catalyzed
reactions
The active site of the enzyme and
the substrate have complementary
shapes
Fit like a lock and key
Enzyme Action
Enzyme – substrate complex
ADP
Enzyme
(hexokinase)
Glucose
Substrates
Products
ATP
Glucose-6phosphate
Products
are released
Active site
Enzyme-substrate
complex
Substrates
are converted
into products
Substrates
bind to
enzyme
Regulation of Enzyme Activity
 Enzymes are affected by any variable
that affects chemical reactions
1.
2.
3.
pH
Temperature
Concentration
of enzyme
1. What happens to chemical bonds during
chemical reactions
Bonds are broken in reactants and new
bonds are formed in products
2. Describe the role of energy in chemical
reactions
some chemical reactions release energy,
and other chemical reactions absorb
energy. Energy changes determine how
easily a chemical reaction will occur
3. What are enzymes, and how are
they important to living things?
Enzymes are biological catylasts.
Cells use enzymes to speed up
virtually every important chemical
reaction that takes place in cells
4. Describe how enzymes work,
including the role of the enzyme
substrate complex
Substrates, the reactants of an
enzyme-catylzed reaction, attach to
the enzyme at an active site and form
an enzyme – substrate complex. Once
the complex is formed, the enzyme
helps convert substrate into product
5. A change in pH can change the
protein. How might a change in pH
affect the function of an enzyme such
as hexokinase (hint: think about the
analogy of the lock and key)
A change in pH could change the shape
of hexokinase. This change would
diminish the ability of glucose and ATP
to bind to the active site of the enzyme.
TEST
TIME