Bio 1107 Exam 1 Study Guide
Chapter 2: The Chemical Basis of Life
Elements and Compounds
An element is a single atom with certain characteristics
A compound is made up of elements, alike and not aka molecule
The four elements that make up 96% of living matter are Hydrogen, Oxygen, Nitrogen,
and Carbon
Atoms and Molecules
A simplified model of an atom misrepresents our understanding of atomic structure
because it does not accurately display how most of an atom is empty space.
A proton is a subatomic particle with a positive charge, a neutron is a subatomic particle
with no charge, or is neutral both are found in the nucleus of an atom and have about
the same weight, which can be expressed as one Dalton
Atomic number is the number of protons an atom contains (symbol A). Mass number is
the sum of the protons and neutrons in an atom (symbol Z). AZX
Atomic weight is the average of all the mass numbers of the naturally occurring isotopes
of one atom based on the abundance of each isotope mass number is a whole number
and atomic weight depends on the mass number
When given the atomic number and the mass number of an atom, you can find the
number of protons and neutrons the atom has using simple math the mass number is the
sum of protons and neutrons and the atomic number is the number of protons, subtracting
the one from the other will result in the number of neutrons
o This type of problem can be seen in various ways with different numbers given
Isotopes are forms of an element with different numbers of neutrons. Isotopes have the
same number of protons and neutrons as each other and only differ in the number of
neutrons. Some can be radioactive though, due to too many neutrons. (C-14)
The valence of an atom is the number of unpaired valence electrons an atom has in its
valence shell.
o An atom’s valence is significant because an atom is most stable when its valence
shell is filled (therefore its valence = 0)
One way shells can be filled is through the formation of strong chemical
bonds (attractions that bind atoms together) like a covalent bond (when
two atoms share one or more pairs of electrons)
Electron Distribution and Chemical Properties
Electronegativity can be defined as a measure of the ability of an atom to attract
electrons toward itself from an atom to which it is bonded this leads to unequal sharing
of electrons in covalent bonds
Nonpolar covalent bonds are covalent bonds where electrons are shared equally or
symmetrically
, Polar covalent bonds are covalent bonds with asymmetric sharing of electrons
Ionic bonds are when electrons are completely transferred from one atom to another
they are not being shared between two atoms, but the charges that result from the transfer
of electrons are what hold the atoms together.
Both strong covalent bonds and weak bonds (like hydrogen bonds) are essential in living
organisms because we need strong bonds to keep things together properly but we also
need weak bonds that can regulate some structures but can also be broken so more
reaction can occur that are needed in life
How would you make up a one molar (1M) solution of ethyl alcohol
o You would add one mole of ethyl alcohol, which would be its molar mass in
grams, to one liter of water
The Properties of Water
Water molecules are polar because the pair of electrons that are being shared between the
oxygen atom and each hydrogen atom are being held more tightly by the oxygen atom
because oxygen is more electronegative than hydrogen. This results in two partial
positive charges on the hydrogen atoms and a partial negative charge on the oxygen atom.
The partial charge on the oxygen is more than the partial charge on the hydrogen
o One water molecule can hydrogen bond with up to four other water molecules
because two hydrogens from two other molecules can bond with the one oxygen,
and the two hydrogen from the original molecule will bond with two more
oxygens from two more molecules.
Four emergent properties of water that are a result of hydrogen bonding
o Cohesion
o Moderation of Temperature
o Insulation of bodies of water by floating ice
o Solvent of life
Cohesion is the attraction between like molecules, like water
Adhesion is the attraction between unlike molecules water adheres to surfaces that
have any polar or charged components
o Cohesion and Adhesion are important in explaining how water can move from the
roots of plants to their leaves against the force of gravity
o Can also see it when water forms a meniscus in a glass tube
Water molecules at the perimeter of the surface adhere to the glass
Water molecules at the surface hydrogen bond with water molecules next
to them and below them, resulting in a net lateral and downward pull that
resists the upward pull of adhesion
o Cohesion is also seen in water’s surface tension
Heat is the total amount of energy possessed by the molecules in a piece of matter;
Temperature is not energy, it is a measure of hotness or coldness based on heat.
Explain the following:
o Coastal areas have milder climates than adjacent inland areas in coastal areas
there is water vapor in the air, much more than inland areas; water has a very high
Chapter 2: The Chemical Basis of Life
Elements and Compounds
An element is a single atom with certain characteristics
A compound is made up of elements, alike and not aka molecule
The four elements that make up 96% of living matter are Hydrogen, Oxygen, Nitrogen,
and Carbon
Atoms and Molecules
A simplified model of an atom misrepresents our understanding of atomic structure
because it does not accurately display how most of an atom is empty space.
A proton is a subatomic particle with a positive charge, a neutron is a subatomic particle
with no charge, or is neutral both are found in the nucleus of an atom and have about
the same weight, which can be expressed as one Dalton
Atomic number is the number of protons an atom contains (symbol A). Mass number is
the sum of the protons and neutrons in an atom (symbol Z). AZX
Atomic weight is the average of all the mass numbers of the naturally occurring isotopes
of one atom based on the abundance of each isotope mass number is a whole number
and atomic weight depends on the mass number
When given the atomic number and the mass number of an atom, you can find the
number of protons and neutrons the atom has using simple math the mass number is the
sum of protons and neutrons and the atomic number is the number of protons, subtracting
the one from the other will result in the number of neutrons
o This type of problem can be seen in various ways with different numbers given
Isotopes are forms of an element with different numbers of neutrons. Isotopes have the
same number of protons and neutrons as each other and only differ in the number of
neutrons. Some can be radioactive though, due to too many neutrons. (C-14)
The valence of an atom is the number of unpaired valence electrons an atom has in its
valence shell.
o An atom’s valence is significant because an atom is most stable when its valence
shell is filled (therefore its valence = 0)
One way shells can be filled is through the formation of strong chemical
bonds (attractions that bind atoms together) like a covalent bond (when
two atoms share one or more pairs of electrons)
Electron Distribution and Chemical Properties
Electronegativity can be defined as a measure of the ability of an atom to attract
electrons toward itself from an atom to which it is bonded this leads to unequal sharing
of electrons in covalent bonds
Nonpolar covalent bonds are covalent bonds where electrons are shared equally or
symmetrically
, Polar covalent bonds are covalent bonds with asymmetric sharing of electrons
Ionic bonds are when electrons are completely transferred from one atom to another
they are not being shared between two atoms, but the charges that result from the transfer
of electrons are what hold the atoms together.
Both strong covalent bonds and weak bonds (like hydrogen bonds) are essential in living
organisms because we need strong bonds to keep things together properly but we also
need weak bonds that can regulate some structures but can also be broken so more
reaction can occur that are needed in life
How would you make up a one molar (1M) solution of ethyl alcohol
o You would add one mole of ethyl alcohol, which would be its molar mass in
grams, to one liter of water
The Properties of Water
Water molecules are polar because the pair of electrons that are being shared between the
oxygen atom and each hydrogen atom are being held more tightly by the oxygen atom
because oxygen is more electronegative than hydrogen. This results in two partial
positive charges on the hydrogen atoms and a partial negative charge on the oxygen atom.
The partial charge on the oxygen is more than the partial charge on the hydrogen
o One water molecule can hydrogen bond with up to four other water molecules
because two hydrogens from two other molecules can bond with the one oxygen,
and the two hydrogen from the original molecule will bond with two more
oxygens from two more molecules.
Four emergent properties of water that are a result of hydrogen bonding
o Cohesion
o Moderation of Temperature
o Insulation of bodies of water by floating ice
o Solvent of life
Cohesion is the attraction between like molecules, like water
Adhesion is the attraction between unlike molecules water adheres to surfaces that
have any polar or charged components
o Cohesion and Adhesion are important in explaining how water can move from the
roots of plants to their leaves against the force of gravity
o Can also see it when water forms a meniscus in a glass tube
Water molecules at the perimeter of the surface adhere to the glass
Water molecules at the surface hydrogen bond with water molecules next
to them and below them, resulting in a net lateral and downward pull that
resists the upward pull of adhesion
o Cohesion is also seen in water’s surface tension
Heat is the total amount of energy possessed by the molecules in a piece of matter;
Temperature is not energy, it is a measure of hotness or coldness based on heat.
Explain the following:
o Coastal areas have milder climates than adjacent inland areas in coastal areas
there is water vapor in the air, much more than inland areas; water has a very high
