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CHAPTER 2
The Chemistry of Life
SECTION 1:
Atoms, Ions, and Molecules
OBJECTIVES
1. What three subatomic particles make up
atoms?
2. How are all the isotopes of an element
similar?
3. 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
DEMOCRITES
DALTON’S ATOMIC THEORY
Dalton performed experiments, unlike Democritus, to
test his theory on atomic structure.
Theory included the following ideas:
All elements are composed of submicroscopic indivisible
particles called atoms.
Atoms of the same element are identical.
Atoms of different elements can physically mix together
or chemically combine with one another in wholenumber ratios to form compounds.
Chemical reactions occur when atoms are separated,
joined, or rearranged.
SUBATOMIC PARTICLES
•
Protons -
Positively charged (+)
•
Neutrons -
Not charged (neutral)
•
Electrons -
Negatively charged (-)
Electrons
Bind together
to form the
nucleus
Protons
Nucleus
Neutrons
WHAT ARE THE 3 MAJOR PARTS
OF AN ATOM?
• Proton
• Neutron
• Electron
DESCRIBE PROTON
• Protons are positively charged particles found in the
atomic nucleus. Protons were discovered by Ernest
Rutherford..
• Experiments done in the late 1960's and early 1970's
showed that protons are made from other particles
called quarks. Protons are made from two 'up' quarks
and one 'down' quark.
DESCRIBE NEUTRON
• Neutrons are uncharged particles found in the atomic
nucleus. Neutrons were discovered by James
Chadwick in 1932.
• Experiments done in the late 1960's and early 1970's
showed that neutrons are made from other particles
called quarks. Neutrons are made from one 'up' quark
and two 'down' quarks.
DESCRIBE ELECTRON
• Electrons are negatively charged particles that
surround the atom's nucleus. Electrons were
discovered by J. J. Thomson in 1897.
• Electrons determine properties of the atom.
Chemical reactions involve sharing or
exchanging electrons.
DESCRIBE NUCLEUS
• The nucleus is the central part of an atom.
It is composed of protons and neutrons.
• The nucleus contains most of an atom's
mass.
• It was discovered by Ernest Rutherford in
1911.
DESCRIBE QUARK
• Believed to be one of the basic building blocks of matter. Quarks
were first discovered in experiments done in the late 1960's and
early 1970's.
• Three families of quarks are known to exist. Each family
contains two quarks. The first family consists of Up and Down
quarks, the quarks that join together to form protons and
neutrons.
• The second family consists of Strange and Charm quarks and
only exist at high energies.
• The third family consists of Top and Bottom quarks and only
exist at very high energies.
DESCRIBE ISOTOPE
• Atoms that have the same number of
protons but different numbers of
neutrons
WHAT IS THE ELECTRON CLOUD MODEL?
• Model of the atom pictures the electrons moving around
the nucleus in a region called an electron cloud.
• The electron cloud is a cloud of varying density
surrounding the nucleus. The varying density shows
where an electron is more or less likely to be. Atoms
with electrons in higher energy levels have additional
electron clouds of different shapes that also show
where those electrons are likely to be.
For more information, click here:
http://regentsprep.org/Regents/physics/phys05/catomodel/cloud.htm
ELEMENT
• A pure substance that consists of
just one type of atom
An elements atomic number = number of
protons
6
C
Carbon
12.011
Atomic number
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
Table Salt
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
HOMEWORK
1. Describe the structure of an atom.
2. Why do all isotopes of an element have the
same chemical properties?
3. What is a covalent bond?
4. What is a compound? How are they related
to molecules?
5. How do Van der Waals forces hold
molecules together?
6. How are ionic bonds and Van der Waals
forces similar? How are they different?
SECTION 2:
Properties of Water
OBJECTIVES
1. Why are water molecules polar?
2. What are acidic solutions?
3. 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
HOMEWORK
1.
Use the structure of a water molecule to explain why its
polar
2.
Compare acidic and basic solutions in terms of their H+
ion and OH- ion concentrations
3.
What is the difference between a solution and a
suspension?
4.
What does pH measure?
5.
The strong acid hydrogen fluoride (HF) can be
dissolved in pure water. Will the pH of the solution be
greater or less than 7?
SECTION 3:
Carbon-Based Molecules
OBJECTIVE
1. What are the functions of each group
of organic compounds?
Interest Grabber
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
HOMEWORK
1. Name four groups of organic
compounds found in living thing
2. Describe at least one function of
each group of organic compounds
3. Compare the structures and
functions of lipids and starches
SECTION 4 & 5:
Chemical Reactions and
Enzymes
OBJECTIVES
1. What happens to chemical bonds during
chemical reactions?
2. How do energy changes affect whether a
chemical reaction will occur?
3. 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 is 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. pH
2. Temperature
3. Concentration
of enzyme
HOMEWORK
1. What happens to chemical bonds during chemical
reactions
2. Describe the role of energy in chemical reactions
3. What are enzymes, and how are they important to
living things?
4. Describe how enzymes work, including the role of
the enzyme substrate complex
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)