A & P Ch. 2 BASIC CHEMISTRY NOTES
MATTER & ENERGY
Matter- anything that takes up space and has mass.
Physical changes do not alter the basic nature of a substance. Ex. Changes in matter,
cutting something into smaller pieces.
Chemical changes do alter the composition of a substance. Often completely changing
the substance.
Energy is massless, takes up no space, and can only be measured by its effects on
matter. Energy is the ability to do work or to put matter into motion.
Kinetic energy is displayed by actually doing work.
Potential energy is the stored energy that objects possess.
**All living things are built of matter, and to grow and function they require a supply
of continuous energy.
Forms of energy
Chemical energy is the energy stored in the bonds of chemical substances.
Electrical energy is the result of the movement of charged particles.
Mechanical energy is directly involved in moving matter.
Radiant energy travels in waves (in the electromagnetic spectrum) ex. X ray, infrared,
light, radio, UV.
Conversion of energy
With few exceptions, energy is easily converted from one form to another.
**In the body, chemical energy of food is trapped in the bonds of a high-energy
molecule called ATP, & ATP’s energy may ultimately be transformed into the electrical
energy of a nerve impulse or the mechanical energy of shortening muscles.
Energy conversions are quite inefficient, some energy is always lost as heat.
**It is heat that makes us warm-blooded animals and contributes to our relatively high
body temperature, which is an important influence on body functioning.
COMPOSITION OF MATTER
So far, 112 elements have been discovered. About 90 of these occur naturally. Only
four elements make up about 96% of the body-carbon, oxygen, hydrogen, & nitrogen.
The building blocks of an element are atoms, and are represented by their atomic
symbols. Atoms where Greek for “not being able to be divided”, but that is not exactly
true, they are composed of subatomic particles. Each subatomic particle differs in mass
and electrical charge, they are protons (p+), neutrons (n0), and electrons (e-). The
electrical charge of a particle is a measure of its ability to attract or repel other charged
particles. (opposites attract, likes repel) Because all atoms are electrically neutral, the
protons must balance the electrons.
Planetary & Orbital models of an atom
The Planetary model of an atom portrays the atom as a mini solar system.
The modern model called the Orbital model, portrays the electron location as an
electron cloud, the region outside the nucleus where you would most likely find an
electron. Most of the volume of an atom is empty space, and nearly all of the mass is
concentrated in the central nucleus.
Identifying Elements
Elements are identified based upon the number of their subatomic particles. The
number of protons must always equal the number of electrons for a balanced atom,
however, the number of neutrons may vary within an element. The smaller (lighter)
elements tend to balance, the larger (heavier) elements may have extra neutrons.
An atomic number is given to each element for identification purposes, it is equal
to the number of protons it contains. The atomic mass number is the sum of all of the
protons and neutrons, electrons do not enter the equation. The atomic weight of an
element is not always the same, due to the variability of the neutrons. An atom with
too many neutrons is referred to as an Isotope. Isotopes of an element have the same
atomic number, it’s the mass that differs. Remember electrons determine bonding
properties so the chemical properties are exactly the same. The heavier isotopes of certain
atoms are unstable and tend to decompose to become more stable, these isotopes are
called radioisotopes. The decomposition is referred to as radioactivity.
**Radioisotopes are used in tiny amounts mark biological molecules so that they can be
traced. PET scans can detect the radioisotopes. Iodine can be used to check blood
circulation through lungs or to scan the thyroid for tumors. Radium, cobalt, and other
radioisotopes are used to destroy localized cancer. ??What is this called??
CHEMICAL BONDS & REACTIONS
When two or more atoms of the same or different elements combine a molecule is
formed. When two or more different atoms bind together a compound is made.
Compounds always have properties quite different from the atoms that made them.
Chemical reactions occur whenever atoms combine with, or dissociate from, other
atoms. When atoms unite chemically, chemical bonds are formed.
Chemical bonds are not physical structures, but a energy relationship that involves the
electrons of the reacting atoms. Chemical bonding occurs in the outer electron shells of
an atom. The maximum number of energy levels (electron shells) known so far is 7.
These levels are number starting at the nucleus outward. The closer the electrons are
to the nucleus the stronger the attraction between the + & - so bonding occurs more
readily in the outer energy levels. Each energy level can only hold a certain number of
electrons. Level one holds 2 electrons, level two holds 8 electrons, level three holds up to
18 electrons and so on. If an energy level is not full or balanced it will try to give, take,
or share electrons with other atoms to obtain a balance. The magic number in all levels
other than one is the number 8. When the outer shell/level has 8 electrons it is inactive
and therefore inert. The outer shell is known as the valence shell and the electrons it
holds are known as valence electrons. The valence electrons determine chemical
reactivity. When atoms give, take, or share electrons they BOND.
Ionic bonds form when a complete transfer of electrons occurs, one atom gives the other
takes. This gives each atom a charge, these charged particles are called ions. The atom
that took an electron now has too many electrons compared to is protons so it has a (-)
charge. It is called an anion (AN-ion). The atom that gave an electron now has too few
electrons compared to its protons so it has a (+) charge. This is called a cation
(CAT-ion). When an ionic bond is created both a cation and an anion are formed.
Since opposite charges stick together these two stay very close.
Ex. NaCl
Covalent bonds form when two atoms share electrons to fill their valence shell at least
part of the time. Many atoms share the electron equally and are referred to as
nonpolar covalently bonded molecules. But some atoms tend to “hog” the electron from
the other atom(s) in the molecule which gives different atoms on the same molecule
slight charges. These are called polar molecules. The “hogging” of the electron may be
due to the three dimensional shape.
Ex. H2O
Hydrogen bonds are weak and sometimes referred to as sticky bonds. They form when
a hydrogen bound to an electron hungry atom (N, O) is attracted to another electron
hungry atom. When polar molecules such as water stick to each other they are forming
hydrogen bonds.
**They are important intramolecular bonds, they help bind different parts of the same
molecule together into a three dimensional shape. (helping it to “fold” neatly)
??What important molecule is dependent on this type of bonding??
Types of reactions
Synthesis reactions- two or more molecules combine to form a larger more complex
molecule. A + B = AB
This always involves bond formation. Energy must be absorbed to make bonds so
synthesis reactions are energy-absorbing reactions.
**Synthesis reactions underlie all anabolic (constructive) activities that occur in body
cells. They are important for growth, repair of tissue, and the formation of protein
molecules by joining amino acids into long chains.
Decomposition reactions occur when a molecule is broken into smaller molecules, atoms,
or ions. AB= A + B
This is a synthesis reaction in reverse. Bonds are always
broken. Products are always smaller & simpler than the original molecule. Energy is
released.
**Decomposition reactions underlie all catabolic (destructive) processes that occur in
the cells. These reactions break down food, and break down glycogen into glucose
when blood sugar level drop.
Exchange reactions involve both synthesis and decomposition reactions. Bonds are
made and broken, a switch is made between molecule parts (change partners).
AB + C = AC + B
or AB + CD = AD + CB
**An exchange reaction occurs when ATP reacts with glucose and transfers its end
phosphate group to glucose forming glucose-phosphate.
** At the same time the ATP becomes ADP. This reaction occurs whenever glucose
enters a body cell, this traps the glucose (fuel) molecule inside the cell.
BIOCHEMISTRY
All chemicals fall are either organic or inorganic compounds.
Organic compounds are carbon containing molecules. Ex. Carbohydrates, lipids,
proteins, & nucleic acids. All organic molecules are large covalently bonded molecules,
with a few exceptions such as carbon dioxide.
Inorganic compounds lack carbon, are simpler, and smaller. Ex. Salt, water, & many
acids & bases.
WATER- the most abundant inorganic compound in the body (2/3). Waters
properties make it so important to us.
 high heat capacity-prevents sudden changes in body temperature.
 Polarity- excellent solvent
 Molecules cannot react chemically unless they are in solution, most chemical
reactions are dependent in the presence of water. Water can act as a transport
and exchange medium in the body.
 Reactant- hydrolysis reactions add water and break bonds.
 Base for all body lubricants.
 Protective function-cerebrospinal fluid-amniotic fluid.
SALTS
The salts of many metal elements are commonly found in the body, but the most
plentiful salts are those containing calcium and phosphorus, found chiefly in bones and
teeth. Dissolved salts are ionic compounds which easily separate into their ions—called
dissociation. Because ions are charged particles, all salts are electrolytes-
Nucleic Acids
Nucleic acids are fundamental:
 they make up genes, provide the blueprints for life, direct growth and
development, and dictate the structure of the proteins.
 They are the largest biological molecule in the body
 Made of C, H, N, & P atoms
 Their building blocks are Nucleotides
 Nucleotides are made out of three basic parts
1. a nitrogen containing base
2. a pentose sugar (5 carbons)
3. a phosphate group
 Nucleotides come in 5 varieties: adenine (A), thymine (T), cytosine (C),
guanine(G), and uracil (U)
 A & G are large two ringed bases, the others are smaller single ringed
structures.
 THERE ARE TWO TYPES OF NUCLEIC ACIDS
1. Deoxyribonucleic acid (DNA) genetic material found within the nucleus of the cell.
 It replicates it’s self before the cell divides, ensuring that every
cell has the exact same genetic material inside.
 It also provides the instructions for building every protein that
your body needs.
 DNA is a double chain of nucleotides which looks like a twisted
ladder, it is called a double helix.
 The bases it uses are A & T which always bond together, and C &
G which always bond together—they are known as
complementary base pairs.
2. Ribonucleic acid (RNA) located outside the nucleus and it is the molecular slave of the DNA.
 It carries out the orders for protein synthesis issued by DNA.
 Single stranded nucleotide chains
 The bases it uses are A & U, and C & G, the U replaces the T and the
sugar is ribose instead of deoxyribose.
 There are three varieties of RNA messenger, ribosomal, and transfer
RNA.
 Messenger RNA carries the info for building proteins from the genes to the
ribosomes, the protein-synthesis.
 Transfer RNA brings amino acids to the ribosomes.
 Ribosomal RNA forms part of the ribosomes, where it oversees the (translation)
of the message and the binding together of amino acids to form the proteins.
ATP
ATP—adenosine triphosphate is a form of chemical energy that is usable by all body
cells. Glucose is the most important “fuel” for the body cells, energy released as glucose
is captured and stored in the bonds of ATP molecules as small packets of energy.
Structurally ATP is a modified nucleotide it consists of an adenine base, ribose sugar, &
three phosphate groups. The phosphate groups are attached by unique chemical bonds
called high-energy phosphate bonds. When they are ruptured by hydrolysis energy is
immediately available. This transforms the ATP to ADP (di-phosphate). ADP builds
up and is replenished back into ATP, by the oxidation of food supplies.