Chemistry Review
AP Biology
Chapter 2: The Chemical Context of Life
Matter, Elements, and Compounds
• Matter
• Anything that takes up space or has mass
• Element
• “Pure” substance that cannot be broken
down
• 92 naturally occurring in nature
• Compound
• Two or more elements combined in a fixed
ratio
Life’s chemical requirements
• 25 of 92 elements are required
• Carbon, nitrogen, hydrogen and oxygen
make up 96% of living matter
• Trace elements
• Required in minute quantities
• Some needed by all life forms
• Others only by certain species
What are
these called?
Atomic Structure
These have
what charge?
These have
what charge?
Reading the periodic table
Isotopes and Radioisotopes
• Isotopes
• Different forms of
element due to # of
neutrons
• Radioisotopes
• Nucleus decays
spontaneously
• Date fossils
• Used to trace atoms
through metabolisms
• Can damage cellular
molecules
Electron configuration
• Energy levels
• Closest shell = least
energy
• Farthest shell = most
energy
• Energy is gained/lost by
moving shells
• Orbital
• 3-D place where e- are
usually found
• 2 e- per orbital
• Valence electrons and
shell
• Outermost e• Complete outer shell =
non-reactive
Chemical Bonding
• Interactions between atoms
• Covalent – shared e• Non-polar covalent
• Polar covalent
• Ion – charged atom
• Anion (-)
• Cation (+)
• Ionic bond – “steals” e-
Weak chemical bonds
• Hydrogen bonds
• Hydrogen atom
covalently bonded to
one electronegative
atom is also
attracted to another
electronegative atom
• Hydrogen bonds,
ionic bonds and
other weak bonds
help form proteins
Reactants and Products
• Chemical reactions
• Make and break chemical bonds, change composition of
matter
• Reactants and products
• Starting and ending materials of chem rxns
• Matter cannot be destroyed, but rearranged
• Most chemical rxns are reversible
• Chemical equilibrium
• When reactions offset one another
• Rxns still happening, but no effect on reactant/product
concentrations
• Reactants and products are NOT equal in concentration
Chapter 3: Water and the Fitness of
the Environment
Polarity and Hydrogen Bonding
• Polar molecule
• Has opposite charges
at different ends
• Each water molecule
can bond to a max of
4 others
Water Properties and Organisms
• Water molecules stick together
due to hydrogen bonds
• In liquid form, bonds are fragile
• Each bond lasts one trillionth a
second
• Cohesion – bonds collectively
hold substance together
• How plants transport water
• Hydrogen molecules tug on
molecules further down the vessel
• http://faculty.pingry.org/thata/pingry_
upload/movies/water_macromolecul
es/cohesion_transport.mov
• Adhesion
• Clinging of one
substance to another
• Surface tension
• Measure of how
difficult it is to break
the surface of a liquid
Water & Earth
• Moderates temperatures,
contributing to habitability
• Kinetic energy
• Energy of motion
• Heat
• Measure of total kinetic energy due to
molecular motion
• Temperature
• Intensity of heat due to avg. kinetic
energy
• Celsius scale
Water and Earth, cont.
• Calorie
• Amount of heat energy
needed to raise 1g of
water by 1°C
• Kilocalorie
• Amount of heat energy
needed to raise 1kg of
water by 1°C
• Joule
• = 0.239 calories (one
calorie = 4.184 J)
Water and Earth, cont.
• Specific heat
• Amount of heat absorbed or
lost for 1g of substance to
change 1°C
• Specific heat of water is 10x
that of iron
• Water resists change in
temp
• High specific heat of water
makes ocean temp stable
for life
• Organisms made mostly of
water resist temp changes
Water and Earth, cont.
• Liquid molecules moving
fast to overcome bonds
enter air as gas
• Vaporization or
evaporation
• Takes 580 calories of heat
to evaporate 1g of room
temp water
• Evaporative cooling
• As substance evaporates,
surface of remaining
substance cools down
Ice Floats
• Why oceans and lakes don’t freeze
• Water is less dense as a solid than
as a liquid
• Expands when frozen
• Reaches its greatest density at 4°C
• If ice sank, all ponds, lakes, and
oceans would freeze solid
• How would this affect life?
Water is the solvent of life
• Solution
• Solvent + solute
• Solvent
• Does dissolving
• Solute
• What dissolves
• Aqueous solution
• Solution with water as solvent
• Water works well, but not for everything,
otherwise could not be stored
Water is the solvent of life, cont.
• Hydrophilic
• Has affinity for water
• Hydrophobic
• Repels water
• Mole
• Equal in # to molecular weight of
substance in grams
• Molecular weight
• Sum of all weights of all atoms in
a molecules
• Avagadro’s number = 6.02 x 1023
(# molecules/mole)
• Molarity
• Moles of solute per liter of
solution
Organisms and pH
• Organisms are sensitive to
pH
• Hydrogen ion
• (H+) single proton with charge
of +1
• Hydroxide ion
• (OH-) charge of -1
• Dissociation
• Transfer of hydrogen atoms
pH
• Acid
• Substance that increases H+ concentration of a
solution
• Donate H+ to a solution
• When hydrochloric acid is added to water HCl  H+
+ Cl• Base
• Substance that increases OH- of a solution
• Concentrations of H and OH
• Products of OH- and H+ concentrations are always
10-14
pH, cont.
• pH scale
• Range from 0-14, expresses OH- and H+
concentrations
• Defined as –log[H+]
• pH declines as H+ concentration increases
• Each pH unit represents 10-fold difference in
OH- and H+ concentrations
pH, cont.
• Buffers
• Substances that minimize changes in pH
• Accepts and donates ions in solution when
needed
• Ex: carbonic acid
Acid Precipitation & Environment
• Threatens the fitness of environment
• Acid precipitation
• Rain, snow, or fog more acidic than pH 5.6
• Harms environment by killing plants and
animals
Chapter 4: Carbon and the
Molecular Diversity of Life
Carbon
• Prominent role in evolution of life
• Can form molecules that are large,
complex, and diverse
• Complexity is demonstrated in
hemoglobin
Organic Chemistry
• Study of carbon compounds
• 30% of a cell is carbon based
compounds
• Common ingredients in carbon
compounds: H, O, N, S, P
Carbon atoms are a versatile building block
• Carbon has 6 electrons
• Little tendency to gain or lose
e- and form ionic bonds
• Completes valence shell by
making 4 covalent bonds
• Makes large, complex
molecules possible
• Carbon is compatible with
many different elements
• CO2 is the source of carbon for
all the organic molecules found
in organisms
Variation = Diversity
• Variation in carbon
skeletons
contributes to the
diversity of organic
molecules
• Carbon chains form
the skeletons of
organic molecules
• Hydrocarbons
• Organic molecules
consisting only of
carbon and hydrogen
Variation = Diversity, cont.
• Isomers
• Compounds with same
molecular formula, but
different structures,
hence different properties
• Structural isomers
• Differ in the covalent
arrangements of their
atoms
Variation = Diversity, cont.
• Geometric isomers
• All have same
covalent
partnerships, differ in
their spatial
arrangements
• Stereoisomers
• Molecules are mirror
images of each other
Functional Groups
• Contribute to the molecular diversity of
life
• Hydroxyl group
• H atom bonded to a O atom, in turn
bonded to the C skeleton
• Alcohol: organic compounds containing
hydroxyl groups
• Polar because of electronegative oxygen
• Carboxyl
• O double bonded to a C, bonded to
hydroxyl
Functional Groups, cont.
• Amino
• N bonded to 2 H atoms
• Sulfhydral
• S bonded to H
• Phosphate
• P ion convalently attached by O atom to C
skeleton
Chemical Elements of Life: Review
• Living matter consists of mainly C, H, O
• Chemical behavior of carbon makes it a
versatile building block