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Chapter 2
The Chemistry of Life
6
C
Carbon
12.011
2-1: The Nature of Matter
• What three subatomic particles make up
atoms?
• How are all of the isotopes of an element
similar?
• What are the two main types of chemical
bonds?
Atoms
• Atoms are the basic unit of matter
• Subatomic particles include protons, neutrons,
and electrons
• Protons (+) and neutrons (neutral) are in the
nucleus and have the
same mass
• Electrons (-) surround the
nucleus and balance out the
charge of the protons
Atomic Structure
Elements & Isotopes
• Elements consist of only one type of atom
• The atomic number is the number of protons
• Isotopes are when the same element has different
numbers of neutrons
• Because they have the same number of electrons,
all isotopes of an element have the same chemical
properties
• Some isotopes are radioactive and can be used to:
– Determine the age of rocks and fossils
– Treat cancer
- Kill bacteria
– Trace movements of substances within organisms
Isotopes of Carbon
Nonradioactive carbon-12
Nonradioactive carbon-13
6 electrons
6 protons
6 neutrons
6 electrons
6 protons
7 neutrons
Radioactive carbon-14
6 electrons
6 protons
8 neutrons
Chemical Compounds
• Chemical compounds are substances
formed by the chemical combination of two
or more elements in definite proportions
– Example: H2O, NaCl
• The properties of compounds can be very
different from the elements that form them
– Example: Sodium and Chlorine
• Table Salt is made from Sodium (Explosive when
mixed with water) and Chlorine (poison gas)
Table Salt
Sodium
Chlorine
Sugar
Carbon
Hydrogen
Oxygen
Chemical Bonds
• Ionic bonds are formed when one or more
electrons are transferred from one atom to
another
• Ions are atoms with positive or negative charges
• Covalent bonds form when electrons are shared
between atoms (can be single, double, or triple)
• Van der Waals forces are slight attractions that
develop between oppositely charged regions or
nearby molecules
Ionic Bonding
Sodium atom (Na)
Chlorine atom (Cl)
Sodium ion (Na+)
Chloride ion (Cl-)
Transfer
of electron
Protons +11
Electrons -11
Charge
0
Protons +17
Electrons -17
Charge
0
Protons +11
Electrons -10
Charge
+1
Protons +17
Electrons -18
Charge
-1
Ionic Bonding
Covalent Bonding
2-1 Section Assessment
1. Describe the structure of an atom.
2. Why do all isotopes of an atom have the same
chemical properties? In what way do isotopes
of an element differ?
3. What is a covalent bond? An ionic bond?
4. What is a compound. How are compounds
related to molecules?
5. How do van der Waals forces hold molecules
together?
6. How are ionic bonds and van der Walls forces
similar? How are they different?
2-2: Properties of Water
• Water is the most abundant compound in
most living things
• Why are water molecules polar?
• What are acidic solutions?
• What are basic solutions?
The Water Molecule
• A water molecule is neutral, however, regions of it
have a slight charge
• The 8 protons in oxygen pull the electrons away
from the hydrogen resulting in a slight – charge
near the O and a slight + charge near the H
(POLAR)
• Hydrogen bonds are weak bonds that form easily
in water and give water some special properties:
– Cohesion – Attraction between molecules of the same
substance
– Adhesion – Attraction between molecules of different
substances
The Water Molecule
WHITE BOARDS:
• Draw a water molecule. Label the Hydrogen and
oxygen atoms. Label the “+” and “-” regions.
Solutions & Suspensions
• A mixture is a material composed of two or
more elements or compounds that are
physically (not chemically) combined
• Solutions involve the even distribution of
components
– Solute – The substance that is dissolved
– Solvent – The substance in which the solute
dissolves
• Suspensions are mixtures of water and
nondissolved material
Solutions & Suspensions
NaCl Dissolving in Water When an ionic compound such as
sodium chloride is placed in water, water molecules
surround and separate the positive and negative ions.
WHITE BOARDS:
• When salt (NaCl) dissolves in water (H2O), salt is
the ___________ and water is the ___________.
WHITE BOARDS:
• A _______________ is a material composed of
two or more elements or compounds that are
physically (not chemically) combined.
*Acids, Bases, and pH
• The pH scale indicates the concentration of H+
ions in solution
• pH scale ranges from 0 (acidic) to 14 (basic) with
7 being neutral (H + = OH-)
• Acids form H+ ions in a solution
• A base is a compound that produces hydroxide
(OH-) ions in a solution (AKA Alkaline)
WHITE BOARDS:
• Draw a line (like the one below). Label Acidic,
Basic, and Neutral. Place the numbers 0, 7, and 14
on the line.
*Buffers
• Maintaining a pH between 6.5 and 7.5 is
important for homeostasis
• The body controls pH with buffers – weak
acids or bases that can react with strong
acids or bases to prevent sharp, sudden
changes in pH
2-2 Section Assessment
1. Use the structure of a water molecule to
explain why it is polar.
2. Compare acidic and basic solutions in terms of
their H+ 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?
2-3 Carbon Compounds
• Organic Chemistry is the study of all
compounds that contain bonds between
carbon atoms
• What are the functions of each group of
organic compounds (carbohydrates, lipids,
nucleic acids, and proteins)?
The Chemistry of Carbon
• Carbon has four valence electrons and can form
bonds with many elements such as H, O, P, S,
and N
• Carbon can also bond to other carbon atoms and
can form chains that are almost unlimited in
length
• Carbon can form single, double, or triple
covalent bonds, and can even form rings
• Carbon is the most versatile element
WHITE BOARDS:
• Carbon has four ____________ electrons.
Macromolecules
• Macromolecules (giant molecules) are made
from thousands or hundreds of thousands of
smaller molecules
• Macromolecules are formed through the process
of polymerization – joining monomers to make
polymers
• The four groups of organic compounds in living
things are carbohydrates, lipids, nucleic acids
and proteins (AKA biomolecules)
Polymerization
WHITE BOARDS:
• Joining monomers to make polymers is called
______________.
WHITE BOARDS:
• Identify the four groups of organic compounds in
living things.
Carbohydrates
• Carbs contain C, H, and O, usually in a 1:2:1 ratio
• Carbs are used as the main source of energy in
living things and can be used for structural
purposes in plants and some animals
• Glucose supplies energy to cells and excess is
stored as starch
• Monosaccharides – single sugars
– Glucose, galactose, and fructose
• Polysaccharides – large molecules formed from
monosaccharides
– Starch, Glycogen (animal starch), and Cellulose
WHITE BOARDS:
• Monosaccharides join to make polysaccharides in
a process called _______________.
WHITE BOARDS:
• What is the ratio of C, H, and O in carbohydrates?
Lipids
• Lipids are made mostly from carbon and hydrogen
• Lipids are generally not soluble in water
• Common categories include fats, oils, waxes, and
steroids
• Lipids store energy and are an important part of
biological membranes and waterproof coverings
• Form when glycerol combines with fatty acids
• Saturated – fatty acid is filled with H’s
• Unsaturated and polyunsaturated – fatty acid has
one or more double bonds and is not filled with
H’s
Lipids
WHITE BOARDS:
• What are the two parts of a lipid?
WHITE BOARDS:
• If a fatty acid chain is completely filled with
hydrogen, it is said to be _______________.
Nucleic Acids
• Nucleic acids contain H, O, N, C, and P
• Nucleic acids are made of nucleotides
– 5-carbon sugar
– Phosphate group
– Nitrogen base
• Nucleic acids store and transmit hereditary
(genetic) information
• DNA and RNA are the two kinds of nucleic
acids
Nucleotide
WHITE BOARDS:
• The three parts of a _____________ are a sugar, a
phosphate, and a base.
WHITE BOARDS:
• Two kinds of nucleic acids are ______________
and ____________.
Proteins
• Proteins contain N, C, H, and O
• Proteins are polymers of amino acids
• Amino acids are composed of:
– Amino group (-NH2)
– Carboxyl group (-COOH)
– R-group (different for each)
• Proteins control reaction rates, regulate cell
processes, form bones and muscles, transport
substances, and fight disease
WHITE BOARDS:
• A protein is a polymer made of monomers called
__________________.
2-3 Section Assessment
1. Name four groups of organic compounds
found in living things.
2. Describe at least one function of each group of
organic compounds.
3. What properties of carbon explain carbon’s
ability to form many different
macromolecules?
4. Explain why proteins are considered polymers
but lipids are not.
5. Compare the structures and functions of the
biomolecules lipids and starches.
2-4: Chemical Reactions & Enzymes
• Everything that happens in an organism is based
on chemical reactions (growth, interactions with
the environment, reproduction, movement, etc.)
• 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?
Chemical Reactions
• A chemical reaction is a process that changes
one set of chemicals into another set of
chemicals
• Reactants form products
CO2 + H2O = H2CO3
• Chemical reactions always involve the
breaking of bonds in reactants and the
formation of new bonds in the products
WHITE BOARDS:
• Identify the reactant(s) for the following:
CO2 + H2O = H2CO3
WHITE BOARDS:
• Chemical reactions always involve the breaking
and reforming of _________________.
Energy in Reactions
• Chemical reactions that release energy often occur
spontaneously
• Chemical reactions that absorb energy will not
occur without a source of energy
– Example 2H2 + O2 = 2H2O
• In order to stay alive, organisms need to carry out
reactions that require energy
• Activation energy is often required to start
reactions that release energy, otherwise all
reactions that release energy would always occur
spontaneously
Chemical reactions that
release energy often occur
spontaneously. Chemical
reactions that absorb energy
will occur only with a source
of energy. The peak of each
graph represents the energy
needed for the reaction to go
forward. The difference between
this required energy and the
energy of the reactants is the
activation energy.
WHITE BOARDS:
• The energy required to start a reaction is called
_________________.
Enzymes
• Many reactions needed for life are too slow or
have high activation energies
• Catalysts are substances that speed up the rate of
a chemical reaction
– Catalysts lower the reaction's activation energy
• Enzymes are proteins that act as biological
catalysts – they speed up reactions that take place
in cells
• Carbonic anhydrase speeds up the reaction
needed to remove CO2 from your body
– CO2 + H2O = H2CO3
Effects of an Enzyme
Enzymes speed up chemical reactions that take place in
cells. Notice how the addition of an enzyme lowers the activation
energy in this reaction. This action speeds up the reaction.
WHITE BOARDS:
• Substances that speed up the rate of chemical
reactions are called _________________. When
they are present within cells, they are called
____________________.
WHITE BOARDS:
• What does “A” represent?
WHITE BOARDS:
• What does “B” represent?
WHITE BOARDS:
• Is this an energy absorbing or energy releasing
reaction?
Enzyme Action
• The enzyme-substrate complex: Enzymes provide
a site where the reactants can be brought together
• Substrates are the reactants of enzyme-catalyzed
reactions
– The substrates binds to the site on the enzyme called
the active site
– The active site and the substrates have complimentary
shapes
– Often described as a lock and key, because each
protein has a specific, complex shape
• Enzymes work best at proper temperature and pH
WHITE BOARDS:
• What are the reactants of an enzyme-catalyzed
reaction called?
WHITE BOARDS:
• The location where the substrate binds to the
enzyme is called the ______________________.
Enzyme Action
2-4 Section Assessment
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 shape of a
protein. How might a change in pH affect the
function of an enzyme such as hexokinase?