-----------Chapter 2 – Chemicals of Life
2.1 – Living organisms are composed of about
25 chemical elements
 Four elements (O, N, C, H) make up about 96%
of the weight of the human body as well as that
of most other living organisms.
o These are the main elements in biological
molecules such as sugar, proteins, and fats.
 Ca, P, K, S, Na, Cl, Mg account for most of the
remaining 4% of the body.
o Involved in the formation of bones, nerve
signaling, and DNA synthesis.
2.2 – Trace elements are common additives to
food and water
 Added to food and water to improve health.
 Trace elements, such as iron ( Fe), are needed
by all living organisms.
o Fe makes up only about 0.004% of human
body mass. Vital for energy processing and
transporting oxygen in your blood.
o Iodine (I) is only needed in small amounts by
certain species.
 Humans require approximately 15 mg of
iodine daily
 Used in the production of a hormone in
the thyroid gland.
 Deficit in iodine results in a condition
called goiter in which the thyroid grows to
abnormal size.
 Adding iodine to table salt has reduced
the occurrence of goiter in many
developed countries.
 Unfortunately, iodized salt is not
available everywhere. Goiters still
affect many people in developing
countries.
o Fluoride, a form of fluorine, commonly
added to municipal water supplies to
prevent tooth decay.
 NOTE: Bottled water does not usually
contain fluoride. Individuals who only
drink bottled water may be more
susceptible to tooth decay and dental
problems.
•Chemicals are added to foods as preservatives to
make them look better.
 Trace elements such as iron and zinc are
often added to cereal, for instance.
 Vitamins, which are made of elements, are
also added to foods.
TONIGHT: Look at a food label on one of your
favorite foods. List the elements and vitamins that
are added to your foods. Also note if the food
provides 100% of the daily required amount for
any of the elements. Bring your label to school
tomorrow.
2.3 – Elements combine to form compounds
 Compound is a substance consisting of two or
more elements combined in a fixed ratio.
o Examples: Table salt : NaCl,
Sugars: Combination of carbon,
hydrogen, oxygen
Water: H2O
Formic Acid (Ants): carbon,
hydrogen, oxygen.
Proteins: carbon, hydrogen,
oxygen, nitrogen, small amounts
of sulfur
 Different arrangements of the atoms determine
different properties of the compounds.
 Compounds have different properties from their
elemental components.
QUESTION: Explain how table salt demonstrates
the theme of emergent properties.
2.4 – Atoms consist of protons, neutrons, and
electrons
 Scientists have split the atom into approximately
a hundred different particles.
 Protons, neutrons, and electrons are the three
subatomic particles that are relevant to the
chemistry of life.
o Protons - positive charge, located in the
nucleus of the atom
o Neutrons – neutral, no charge, located in the
nucleus of the atom
o Electrons – negatively charged, located in the
electron cloud surrounding the nucleus
 The attractive force between the positively
charged proton and the negatively charged
electron is what keeps the electrons orbiting the
nucleus of the atom at about the speed of light.
 All atoms of a particular element have the same
number of protons in their nucleus.
 An atom’s mass number is equal to the number
of protons and neutrons in its nucleus.
 The mass of a proton and the mass of a neutron
are almost identical and expressed as a unit of
measurement called dalton. An electron has
approximately 1/2000 of the mass of a proton.
 The mass of an atom is the sum of the mass of
its protons and neutrons.
 The atomic mass number is approximately
equal to an atom’s mass number.
 Isotopes: atoms of the same element with
different numbers of neutrons in the nucleus.
o 99% of Carbon that occurs in nature has 6
protons and 6 neutrons, with an atomic mass
of approximately 12.The remaining 1% of
Carbon has 6 protons and 7 neutrons; Called
Carbon 13. A very small amount is Carbon
composed of 6 protons and 8 neutrons;
called Carbon 14.
 Carbon 14 is unstable or radioactive.
Radioactive isotope is one in which the
nucleus decays spontaneously, giving off
particles and energy. Radiation given off by
decaying isotopes can damage cellular
molecules and are thus dangerous to living
organisms. Some radioactive isotopes can be
helpful, such as Carbon 14 in dating fossils.
Some radioactive isotopes are also useful in
biological research and medicine.
2.5 Radioactive Isotopes can help or harm us.
•Living cells cannot distinguish between isotopes
of the same element and take up the radioactive
isotopes in the usual way. These radioactive
isotopes can be used as tracers, biological spies,
for monitoring the fate of atoms in living
organisms.
 Basic Research: Use radioactive isotopes
to trace the chemical changes molecules
undergo in living organisms. Photosynthesis:
scientists have used radioactive Carbon 14 in
plants. Carbon 14 has allowed scientists to
trace the sequence of molecular changes
CO2 goes through as glucose is formed.
 Medical Diagnosis: Radioactive isotopes
are used in small amounts in some imaging
techniques or medical tests to diagnosis
diseases.
o Kidney disease: small amount of
radioactive isotope is introduced into the
blood and taken up by the kidneys. The
urine is analyzed to measure the amount of
radioactive isotope present.
 Radiology: Radioactive isotopes are used in
imaging techniques, such as PET scans, to
detect certain heart disorders, cancers, and
in brain research. Current Alzheimer’s
disease uses a protein, PIB, which contains a
radioactive isotope that can be detected by a
PET scan. PIB binds with beta-amyloid which
is a protein that creates plaques and deposits
in the brain as Alzheimer’s progresses. New
therapies in treating Alzheimer’s focus on
limiting the production or reducing the
amount of beta-amyloid deposits. PIB allows
scientists to monitor the effectiveness of the
new drug therapy.
Dangers:
 Uncontrolled exposure to radioactive isotopes
can damage molecules, especially DNA, in
living organisms.
o Particles and energy from the decaying
isotope can break chemical bonds or cause
abnormal bonds to form.
 Manmade Sources of Exposure:
o Example: Chernobyl, Ukraine (1986)
 Nuclear reactor explosion
 30 people died within a few weeks
 Increase in cancer, thyroid
 Increase in birth defects
 Thousands increased risk of cancer
 UN predicted 4,000 deaths to be
attributed to accident
 Natural Sources of Exposure:
o Radon:
 Naturally occurring gas from decaying
uranium in underlying bedrock/rocks
 Can cause lung cancer
 Homes can be tested
 Sensors can be installed
 Technology exist to remove radon from
homes
2.6 Electron arrangement and chemical
properties of an atom
 Directly involved in chemical activity of atom
 Vary in amount of energy – farther from
nucleus, greater the energy
 Valence electrons determine chemical
properties of an atom
 Atoms with unpaired electrons in outer shells
bond with other atoms/are involved in chemical
reactions (reactive)
 O,C,H,N the main components of biological
molecules, react readily with other atoms
 Noble gases are inert because the outer
electron shell is full (nonreactive)
2.7 Ionic bonds
 Electrons are gained or lost
 Atoms losing electrons become positively
charged.
 Atoms gaining electrons become negatively
charged.
 Charged atoms are called ions
 Oppositely charged ions are attracted to one
another and form chemical bonds/ionic bonds
 Ionic bonds form compounds which are
electrically neutral
 Metal to nonmetal
2.8 Covalent bonds
 Two atoms share one or more pairs of valence
electrons
 2 or more atoms held together by covalent
bond(s) form molecules
 Nonmetal to nonmetal
 Can be represented in 4 forms (page 23)
o Molecular formula – H2
o Electron distribution model –
o Structural formula
o Space Filling Model
2.16 Acid Precipitation & Ocean Acidification
 Contamination of rivers, lakes, seas, and
precipitation pose serious environmental
problems.
o Acid Rain
o International Paper Waste Water Release
in Pearl River
o Dead Zone in Gulf of Mexico
 Can result in change of pH (the measure of
acidity or alkalinity of a substance)
 CO2 released from burning of fossil fuels mixes
with water and changes the pH of H2O
 Sulfur Oxides and nitrous oxides are also
released which results in the formation of acid
rain and snow.
 Acid precipitation – rain/snow/fog with pH lower
than 5.6
o pH between 2 and 3 more acidic than
vinegar
o Eastern US
 Kills fish, damages other forms of life
 Changes soil chemistry
 Negatively affects some forest in N.
America and Europe
o CO2 levels in atmosphere continue to
increase
 Acts as reflective blanket/holds heat in
atmosphere
 Absorbed by ocean which changes the
chemistry of the ocean
 Lowers pH of seawater
 Reduces concentration of carbonate
which corals use to produce calcium
carbonate/builds up their skeleton
(calcification)
 Decreased calcification can interfere
with marine food webs/reproduction
of marine life.
2.17 The Search for Extraterrestrial Life Centers
on Search for H2O
 Space probes
 Comet probe
 Moon Exploration
 Mars polar ice caps
 Search for H2O because it is so important for
life as we know it.
2.8 – Chemical Reactions
 Make or break bonds
 Changes composition of matter
 Structure of atoms and molecules determine
behavior
 Reactants – starting material in a chemical
reaction
 Products – molecules produced during a
chemical reaction
 # of atoms in the reactants = the # of atoms in
the products
 Matter is neither created nor destroyed, only
rearranged into new molecules
 Living things routinely carry out chemical
reactions; most involve Carbon-based
compounds.
EX: C6H12O6 + 6O2
6CO2 + 6H2O
What chemical reaction/process is represented
by the equation above?