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Chemistry of Life
BIOL-101 Section 800RL
Mr. Fusco
Chapter 2: The Chemical Context of Life
Chapter 3: Water and the Fitness of the Environment
Matter
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Organisms are composed of matter
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An ______ is a substance that cannot be
broken down to other substances by chemical
reactions
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______ is anything that takes up space or has mass
Matter is made up of elements
Organized into ______ ______ __ ______
______ ______ usually first letter or two
A ______ is a substance consisting of two or
more elements in a fixed ratio
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A compound has characteristics different from those
of its elements
Example = Sodium Chloride (NaCl)
Fig. 2-3
Compound Example
Sodium
Chlorine
Sodium
chloride
Essential Elements of Life
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About 25 of the 94 naturally occurring elements
are essential to life
Carbon, hydrogen, oxygen, and nitrogen make up
96% of living matter
Most of the remaining 4% consists of calcium,
phosphorus, potassium, and sulfur
______ ______ are those required by an
organism in minute quantities (less than 0.01%)
What are You Made of?
Human composition
1) Oxygen 65%
2) Carbon 18.5%
3) Hydrogen 9.5%
4) Nitrogen 3.3%
5) Calcium 1.5%
6) Phosphorus 1%
7) Potassium 0.4%
8) Sulfur 0.3%
9) Sodium 0.2%
10) Chlorine 0.2%
11) Magnesium 0.1%
Trace Elements
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Micronutrients
Minute, “trace”, quantities
Vitally Important
Ex. cobalt, copper, chromium, fluorine,
chlorine, iron, iodine, manganese,
selenium and zinc
Website defining elements
Atoms
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Each element consists of
unique atoms
An ______ is the
smallest unit of matter
that still retains the
properties of an element
Smallest particle of an
element that has the
characteristics of that
element (elements are
built from one kind of
atom)
Atoms
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Atomic ______
-protons
-neutrons
Proton number (atomic number) determines the
type of element
Electrons form a cloud around the nucleus
Neutron mass and proton mass are almost
identical and are measured in daltons
______ ______ = number of protons
______ ______ = proton # + neutron #
Atomic Structure
Atomic Structure
Particle
Symbol
Charge
Location
p+
Mass
(amu)
1
Proton
Positive (+)
Inside
Nucleus
Neutron
n
1
None
Inside
Nucleus
Electron
e-
.000545
Negative (-)
Outside
Nucleus
Reading the Periodic Table
6
Atomic Number
C
(# of protons)
Atomic Symbol
Carbon
12.011
Element Name
Atomic mass
(# of protons + # of neutrons)
Electric Charges
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The negative charge of the electron is the
same magnitude as that of the proton
(equal but opposite)
An atom is electrically ______ .
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#protons = #electrons
Electron Energy Levels
 ______ is the capacity to cause change
 ______ ______ is the energy that matter has
because of its location or structure
 The electrons of an atom differ in their amounts of potential
energy
 An electron’s state of potential energy is called its energy
level, or ______
______
Electron Energy Levels
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Electrons fill different “shells”
-1st shell: up to ______
-2nd shell: up to ______
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-3rd shell: up to ______
Shells are filled from inner to outer
Atoms will take or give electrons to attain a full outer
shell (______ )
Atoms with full shells typically don’t react
When drawing
an atom like
this, it is called
a Bohr model.
Electron Distribution
Electrons help determine the chemical behavior of an
atom
The periodic table of the elements shows the electron
distribution for each element
______ ______ are those in the outermost shell,
or ______ ______
Specifically, the chemical behavior of an atom is
mostly determined by the valence electrons
Elements with a full valence shell are chemically
______(not chemically active)
Ions and Isotopes
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___________
-(+) or (-) charged particle
-What would have to happen for an atom to
become an ion?
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___________
-atoms of the same element with different
numbers of neutrons
All atoms of an element have the same number
of protons but may differ in number of neutrons
Carbon Isotopes:
What differs?
12
6
C
13
6
C
14
6
C
___________
6 neutrons
7 neutrons
8 neutrons
Radioactive Isotopes
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Occurs when nuclei of unstable isotopes break apart
Used as ______ in medicine and research
Dangers:
-Nuclear explosions
-Radon (2nd most frequent cause of lung cancer)
Some applications of radioactive isotopes in biological
research are:
 Dating fossils
 Tracing atoms through metabolic processes
 Diagnosing medical disorders
Drawing Atoms
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Using the periodic table, write the following
information on your atom on an index card:
 Symbol
 Atomic #
 Atomic mass
 Element name
 Sketch your model (Bohr model)
 Is the outermost electron shell filled
 Will this element readily react with others? Why
or why not?
Chemical Bonding
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Atoms of different elements interact to form ______
These interactions usually result in atoms staying close
together, held by attractions called ______ ______
Bonding gives a molecule completely different chemical
properties than its parent elements
Example:
______ ______, NaCl (table salt) = nontoxic
vs.
______ is a metal that is violently reactive with
water. If sodium comes into contact with water, the
hydrogen gas that is released will actually burst into
flames
Chemical Bond Types
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3 Types of Chemical Bonds
-Covalent bond
-Ionic bond
-Hydrogen bond
Covalent Bonds
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Electron ______
Usually between 2 nonmetals
Strongest bond
Multiple covalent bonds can form if they need
more than one electron to fill their outer shell
______ ______ = sharing of one pair of valence
electrons
______ ______ = sharing of two pairs of
valence electrons
Covalent Bonds
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The notation used to represent atoms and
bonding is called a __________ ________
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For example, H–H
This can be abbreviated further with a
__________ __________
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For example, H2
Covalent Bonds
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Found in most compounds in organisms
A ___________ is a group of atoms held together
by covalent bonds having no overall charge
 ________________ is an atom’s attraction for the
electrons in a covalent bond
 The more electronegative an atom, the more
strongly it pulls shared electrons toward itself
Examples: Sugars, fats, proteins, water
What is a diatomic molecule? Polyatomic?
Covalent Bond Types
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___________ covalent
-equally shared electrons
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___________ -covalent
-One atom has a greater affinity for electrons in a
molecule (more electronegative)
-Shared electrons will spend more time around that atom
-Unequally shared electrons will cause a partial electrical
charge (called a _______ ) to form across the molecule
Polar vs. Non-Polar
Covalent Bonds
Non-Polar Covalent Bond
Polar Covalent Bond
2 H atoms equally sharing electrons
A dipole caused by the polar
covalent bond of the water
molecule.
Weak Bonds
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Most of the strongest bonds in organisms are
covalent bonds that form a cell’s molecules
Weak chemical bonds, such as ___________
bonds and ___________ bonds, are also
important
Weak chemical bonds reinforce shapes of large
molecules and help molecules adhere to each
other
Ionic Bonding
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Electron ___________
Atoms sometimes strip electrons from their
bonding partners
After the transfer of an electron, both atoms have
charges
Remember, a charged atom (or molecule) is called
an ___________
The oppositely charged ions attract to form an
___________ ___________
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An example is the transfer of an electron from
sodium to chlorine
Ionic Bonding
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Usually between 2 metals, or a metal and a nonmetal
Example:
-Na (Sodium)
Atomic number = 11
How many electrons in outermost shell?
How many electrons to fill outer shell?
-Cl (Chlorine)
Atomic number 17
How many electrons in outermost shell?
How many electrons to fill outer shell?
Ionic Bonding:
Na and Cl
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an electron and
becomes positively charged (Na+)
___________ ___________ an electron becoming
negatively charged (Cl-)
Both atoms now become ions
___________ charges on the Na+ and Cl- ions
cause them to attract each other and form an
ionic bond
Na+ + Cl-  NaCl
___________ ___________
Ionic Bonding:
Na and Cl
Ionic Bonding
A ___________ is a positively charged ion
An ___________ is a negatively charged ion
An ionic bond is an attraction between an
anion and a cation
Compounds formed by ionic bonds are called
ionic compounds, or ___________
Salts, such as sodium chloride (table salt),
often found in nature as crystals
are
Hydrogen Bonding
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Water molecules have polar (charged) ends
A ___________ bond forms when a hydrogen atom
covalently bonded to one electronegative atom is also
attracted to another electronegative atom
Allows for hydrogen bonding with other water molecules
H-bonding holds water molecules together
Weak bonds resulting from:
-attraction of ___________ ___________ H-atom on 1
water molecule to ___________ ___________ Oatom in another molecule
Resulting in water molecules clinging together
Water Movie
Van der Waals forces
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Electrons in a molecule are in random motion
around the nuclei.
The movement of electrons can cause an
___________ distribution of the electron cloud,
creating ___________ areas of slightly positive and
negative charges
When molecules come close together, the attractive
forces between these positive and negative regions
pull on the molecules and hold them together.
The strength of the attraction depends on the size
of the molecule, the shape and its ability to attract
electrons.
Water (Agua)
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Water is the biological medium on Earth
All living organisms require water more than any other
substance
Most cells are surrounded by water, and cells themselves
are about ___________ water
The abundance of water is the main reason the Earth is
habitable
The water molecule is a ___________ ___________ : The
opposite ends have opposite charges
___________ allows water molecules to form hydrogen
bonds with each other
Properties of Water
 Four of water’s properties
that facilitate an
environment for life are:
 Cohesive/Adhesive
behavior
 High Specific Heat
 Expansion upon freezing
 Universal solvent
Cohesive Forces
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___________
-water molecules are
attracted to other
water molecules
___________
___________ =
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cohesion of water
molecules at the
surface of a body of
water
Example:Water
strider bug (right) &
Basilisk (aka Jesus
lizard)
Adhesive Forces
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___________
-Water is attracted to other materials
Example: ______ ______ in a straw
-water “climbs” up a straw
-water molecules are attracted to the
straw molecules
-When one water molecule moves closer
to the straw molecules the other water
molecules (which are cohesively attracted
to that water molecule) also move up into
the straw
Plants use capillary action to draw water
from the ground into themselves
High Specific Heat Index
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Water can absorb a lot of heat before it begins to get hot since
-hydrogen bonds ___________ breaking
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-it takes much energy before bonds break, releases lots
before rejoining
Example: Moderates temperature on Earth
High Specific Heat Index
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Water absorbs heat from warmer air and releases
stored heat to cooler air
Water can absorb or release a large amount of heat with
only a slight change in its own temperature
is a measure of the total amount of
kinetic energy due to molecular motion
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___________ ___________
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___________
is the energy of motion
measures the intensity of heat due to the
average kinetic energy of molecules
Evaporative Cooling
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___________ is transformation of a substance from
liquid to gas
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___________ ___ ___________ is the heat a liquid
must absorb for 1 g to be converted to gas
As a liquid evaporates, its remaining surface cools, a
process called ___________ ___________
Evaporative cooling of water helps stabilize temperatures
in organisms and bodies of water
Hottest water molecules leave first, reducing the average
temp. of those remaining
Examples:
-Cools tropical oceans
-Keeps coastal areas more moderate
Physical States
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Which is most dense: solid, liquid, gas?
Usually solid, but in water, liquid is most
dense
As a result, when water freezes it floats
-hydrogen bonding
What if ice did not float?
Insulation of Bodies of
Water by Floating Ice
Ice floats in liquid water
because hydrogen bonds in ice
are more “ordered,” making
ice less dense
Water reaches its greatest
density at ___________
If ice sank, all bodies of
water would eventually freeze
solid, making life impossible
on Earth
Universal Solvent
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Water dissolves more substances than any other liquid.
A ___________ is a mix of 2 or more substances
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A ___________ is a dissolving agent
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A ___________ is what dissolves
Polar substances dissolve in water (like dissolves like)
An ___________ solution is one in which water is the
solvent
Chemical reactions of living things
Dissolving animation
Hydrophilic & Hydrophobic
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A ___________ substance is one that has an affinity for
water
A ___________ substance is one that does not have an
affinity for water
Oil molecules are hydrophobic because they have
relatively nonpolar bonds
A ___________ is a stable suspension of fine particles
in a liquid
Most biochemical reactions occur in water
Chemical reactions depend on collisions of molecules
and therefore on the concentration of solutes in an
aqueous solution
Acids and Bases
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A hydrogen atom in a hydrogen bond between
two water molecules can shift from one to the
other:
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The hydrogen atom leaves its electron behind and is
transferred as a proton, or ___________ ion (H+)
The molecule with the extra proton is now a
___________ ion (H3O+), though it is often
represented as H+
The molecule that lost the proton is now a
___________ ion (OH–)
Acids and Bases
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Some water molecules dissociate (come apart) in
a solution forming:
1) H+ (hydrogen ions)
2) OH- (hydroxide ion)
___________ release H+ into a solution
___________(alkaline solutions) take in H+ ions
and release OH- ions
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Acids & bases are quantified on a ___________
which is a measure of hydrogen ion
concentration in a solution
pH Scale
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Acidic solutions have
pH values less than 7
Basic solutions have
pH values greater
than 7
Water is neutral (pH
= 7)
Most biological
fluids have pH
values in the range of
6 to 8
Buffers
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The internal pH of most living cells must remain close to
pH 7
___________ are substances that minimize changes in
concentrations of H+ and OH– in a solution
Most buffers consist of an acid-base pair that reversibly
combines with H+
The majority of biological processes carried out by cells
occur between pH _____________________ .
In order to maintain homeostasis it is important to control
H+ levels.
Have you have ever taken an antacid?
 This acts as a buffer to help neutralize acids.
Your blood contains buffers that keep the pH at 7.4.
Threats to Water Quality
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___________ ___________
refers to rain, snow, or fog
with a pH lower than 5.6
Acid precipitation is caused mainly by the mixing of
different pollutants with water in the air and can fall at
some distance from the source of pollutants
Acid precipitation can damage life in lakes and streams
Effects of acid precipitation on soil chemistry are
contributing to the decline of some forests
Human Activities
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Human activities such as burning ___________
___________ threaten water quality
___________ is released by fossil fuel combustion
and contributes to:
 A warming of earth called the “___________ ”
effect
 Acidification of the oceans; this leads to a
decrease in the ability of corals to form calcified
reefs
Questions???