A&P I
Chapt 2 Notes
Chemical Organization of the Body
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1. Matter – Anything that occupies space and has mass.
2. Mass – a measure of the amount of matter
i. Weight- the force gravity has on a mass of matter
3. Chemicals – matter is made of chemicals
i. Element- pure substance all the matter of an element is made up of
identical atoms.
1. Atom- the smallest chemical particle of an element that retains
all the properties of that element
i. Nucleus – the central part of an atom made up
of:
1. Proton – elemental particle with a positive
charge
a. The number of protons in an atom
defines the element
b. The number of protons is called the
atomic number of the element
2. Neutron – elemental particle with no
charge that has the same mass as a proton
a. The number of protons plus the
number of neutrons is called the
atomic mass of the element
b. Two atoms of the same element with
differing atomic mass will have the
same number of protons but will have
a different number of neutrons they
are called isotopes.
c. Some isotopes are radioactive
isotopes and are unstable. They will
gradually decay toward a stable
state.
i. The time it takes for half of the
starting amount of an isotope
to decay to the next more
stable state is called the halflife
ii. Often the decay of radioactive
isotopes will change the
number of protons in the
nucleus and result in a
different element.
iii. Radioactive isotopes emit
particles that can be detected
and some make valuable
tracing elements for medical
diagnosis.
iv. Some radioactive isotopes are
harmful to cells.
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Chapt 2 Notes
Chemical Organization of the Body
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v. The harmful radioactivity can
be used to treat cancer
ii. Electron – subatomic particle circulating about
the nucleus having a negative charge equal to the
positive charge of the proton, but having
negligible mass.
1. Electrons are grouped in energy levels or
shells about the nucleus.
a. Shell one can contain a maximum of
2 electrons
b. Successive shells contain a maximum
of 8 electrons
c. Proximal shells must be filled before
electrons are placed in higher shells
d. The shell containing electrons further
from the nucleus is called Valence
band
e. The valence bands of atoms
participate in chemical bonding of
atoms to form molecules.
f. If the valence band is full and the
atom is not charged the atom stable
and is not free to react chemically
g. Atoms “desire” to have complete
valence bands and react with each
other in ways to move toward
satisfying the valences. (See
Chemical Bonds Below)
2. A complete atom has an equal number of
positively charged protons and negatively
charged electrons, making the atom as a
whole neutrally charged.
a. If an atom loses or gains an electron
it is a charged atom called an ion.
i. If an atom loses an electron it
has more protons than
electrons, therefore, the atom
has a positive charge and is
called a cation.
ii. If an atom gains an electron it
has more electrons than
protons and has a net negative
charge. It is called an anion.
4. There are 92 naturally occurring chemical elements
a. 25 of these are essential for human life.
i. 96 % of the body is composed of only 4 of these 25 (C,H,O,N)
ii. The body is over 75% water so the H2O is a substantial percentage of
the body mass
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Chapt 2 Notes
Chemical Organization of the Body
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1. Oxygen is the largest of the C H O N molecules making up 65%
of the mass of the body
2. Carbon follows at 18.5% of the body mass
3. many small Hydrogen atoms make up 9.5% and
4. the element found in all protein, DNA, and RNA (Nitrogen)
makes up 3.2%
5. Chemical Bonds may create bonded atoms of the same element such as O2 or
bonded atoms of different atoms forming a compound such as carbon monoxide
CO,
There are three main types of chemical bonds:
a. Ionic Bond- When and anion and cation are held together in a chemical
bond by electrical attraction Example:
i. Sodium (Na) has 11 protons and 11 electrons. The electron
configuration of Na is 2,8,1. That is 2 electrons in the innermost shell,
eight in the second shell and only one in the valence shell. Na will
easily give up its single outer electron to achieve an octet valence
band making it a positively charged cation (Na+).
ii. Chlorine (Cl) has 17 protons and 17 electrons. The electron
configuration is 2,8,7. Cl will readily accept an additional electron
filling its valence band making it an anion (Cl-).
iii. The two new ions are held together by the electric attraction of
opposite charges making a new molecule with no overall net charge.
(NaCl) this is an example of an Ionic bond.
b. Covalent bond – if neither atom gives up or gains an electron but come
into a permanent proximity to each other such that they share their valence
electrons to satisfy the valences of both atoms they are covalently bonded.
i. If one electron is shared it is a single bond
ii. If two electrons are shared it is a double bond
iii. If three electrons are shared it is a triple bone.
iv. If the electrons are not shared equally, and atoms at one end of the
molecule spends more time with the electron than an atom at the
other end of the molecule the molecule has a partial negative at one
end and a partial positive at the other end. We say the molecule is
electrically polarized, and we have a polar covalent bond.
c. If polar covalent molecules are attracted and held in proximity to each other
by the opposite charges on the opposite ends of the molecule this is called
hydrogen bonding. Example: Water (H2O)
i. The oxygen atom has a stronger attraction for the electrons than does
the hydrogen atom and is said to have a greater electronegativity.
ii. Due to the electronegativity of the oxygen the hydrogen’s electrons
will be unequally drawn to the oxygen leaving the hydrogen with a
lower percent of electron time. Therefore, the oxygen end of the
water will exhibit a negative charge and the hydrogen will have a
positive charge. Adjacent water molecules will have hydrogen bonding
between the hydrogen and oxygen atoms.
A&P I
Chapt 2 Notes
Chemical Organization of the Body
Hydrogen
bond
O
O
H
p4/8
H
H
H
O
O
H
O
H
H
H
H
O
O
H
H
H
H
H
iii. Water having many hydrogen bonds has a strong surface tension at
the outer layers of H2O molecules. If this surface tension is not broken
the wet surfaces of the alveoli sacs in the lungs would stick tightly
together making breathing difficult.
iv. Hydrogen bonding holds the two strands of DNA together.
6. Chemical Reactions are the making and breaking of chemical bonds when
molecules are taken apart or assembled.
a. The starting substances are called reactants
b. The resulting molecules are called products
c. A listing of the chemical symbols in a molecule is called its chemical formula.
i. Example: The formula H2O indicates that that there are two atoms of
hydrogen and one atom of oxygen in a molecule of water.
d. A symbolic representation of a chemical reaction is called a chemical
equation.
i. Example: the equation: H2O + CO2
H2CO3 shows that the
reactants water and carbon dioxide can react and form a new
molecule called carbonic acid.
ii. In order for a chemical equation to be balanced there must be the
same number and kind of atoms on both sides of the arrow.
1. Example: hydrogen molecules H2 can combine with Oxygen
molecules to make water.
H2 + O2
H2O This reaction is not balanced. To show the
correct ratio of molecules in to molecules out the same number
of Hydrogen and oxygen atoms must appear on both sides of
the equation: 2H2 + O2
2H2O is a balanced equation
showing the correct ratio of molecules in and out. We have 4
hydrogen atoms on the left and 4 on the right with two
oxygens on the left and two on the right.
e. Metabolism = all the chemical reactions occurring in the body Metabolism
occurs in two forms:
i. Catabolism – the breaking down or decomposition of molecules.
ii. Anabolism – the making or synthesis of new molecules.
f. Chemical reactions involve energy exchange.
i. Energy can not be created or destroyed it can only change form. This
is called the law of conservation of energy
ii. Energy may be due to the motion a mass has and is called kinetic
energy
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Chemical Organization of the Body
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iii. Energy may be due to position of mass or masses called potential
energy.
1. The energy due to chemical bonds is potential energy called
chemical energy.
a. When chemical bonds are broken energy is released.
When energy is released in a reaction it is referred to a
an Exergonic reaction. An exothermic reaction is an
exergonic reaction in which the form of energy released
is heat.
b. When chemical bonds are made potential energy must
be put into the bonds. This is called an Endergonic
reaction.
c. In a typical chemical reaction some bonds are broken
and some new bonds are formed. The overall reaction
may be endergonic or exergonic.
d. Example: glucose (C6H12O6) is broken down into C + H2O
in an exergonic process.
i. Some of energy released is recaptured in an
endergonic process of producing an energy
currency molecule called ATP (adenosine
triphosphate)
ii. ATP is an energy carrier that is used in many other
chemical processes to release energy to that
process by the exergonic process of:
ATP
ADP + PO4
1. the energy released by converting ATP to
ADP (adenosine diphosphate) is directly
coupled to other endergonic reactions.
iv. In order for a chemical reaction to occur molecules must collide with
each other correctly oriented and with enough force to disrupt the
valence bonds in the existing chemical bonds so new bonds can form.
The required energy is called the Activation energy.
v. The rate of a chemical reaction may be increased by:
1. Increasing the concentration of reactants so that collisions
occur more frequently.
2. Adding energy such as heat energy so that the molecules move
faster and collide with more force.
3. Lowering the activation energy required. If the molecules could
have more collisions with the molecules oriented such that
maximum disruption of valence bonds occurred the activation
energy would be less. A catalyst added to a reaction lowers
the activation energy and speeds up a reaction.
a. Catalysts in the body are special proteins called
enzymes.
b. Catalysts are not used up or contained in the product.
They are used over and over in a reaction.
4. The rate of a reaction can be controlled by controlling the
amount of catalyst (enzyme) present with the reactants.
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Chapt 2 Notes
Chemical Organization of the Body
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g. Chemical reactions may be reversible this is shown with a double arrow
between the reactants and products.
i. Example: CO2 + H2O
H2CO3
H+ + HCO3ii. The reaction will go back and forth with an equilibrium distribution of
each chemical at all times.
iii. The reaction will obey the law of mass action: i.e. if more CO2 is
added to the reactants it will result in more H+ and HCO3 being
produced and if CO2 is removed then H+ and HCO3 will be removed
from solution keeping the equilibrium. If more HCO3 is added then
more CO2 will be produced.
7. Inorganic and Organic Compounds and Solutions
a. The chemistry of carbon is called organic chemistry.
i. Organic chemical reactions involve carbon and usually hydrogen.
ii. Organic reactions are usually covalent.
iii. Carbon has 6 protons and 6 electrons. Its electron configuration is 2,4
iv. Carbon needs 4 more covalent electrons to satisfy its valence octet,
and always has 4 chemical bonds.
v. Life forms on earth are classified as carbon based life forms because
we have so many carbon bonds in the structure of our tissues,
enzymes, hormones etc.
b. The most important non-organic chemical on earth is Water.
i. Because water is polar it is a good solvent for many ionic compounds.
1. Solvent – substance that dissolves another, usually is a liquid.
2. Solute – that which gets dissolved, may be solid, liquid, or
gas.
3. Solution – the resulting mixture made from solvent and
solute.
ii. A solute that disassociates (dissolves) in water and forms ions is
called an electrolyte.
1. Solutes that are charged molecules or form ions dissolve easily
in water due the water’s bent shape and polar charges, which
allow a water molecule to interact with several charged groups.
a. These substances are said to be hydrophilic
iii. Non polar molecules are not very soluble in water and are said to be
hydrophobic or water fearing.
iv. Water not only dissolves ionic compounds, but is also a reactant or
product in many organic reactions. (See protein dissolution and
assembly below)
1. Dehydration synthesis – is the dehydration or removal of water
from reactants and synthesizing new molecules.
2. Hydrolysis – is the addition of water to a molecule to lyses or
break the molecule apart.
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Chapt 2 Notes
Chemical Organization of the Body
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v. Water has a high heat capacity which means that it can absorb heat
without a significant rise in temperature, therefore, helping to
maintain a relatively constant body temperature.
vi. Water has a high heat of vaporization. Which means that as water
evaporates it absorbs a significant amount of heat. Water (sweat) is
used for evaporative cooling of the body.
vii. Water also acts a lubricant where internal organs touch and slide over
each other, and as a lubricant in joints. It is also the principal
component of mucus lubricating fluid.
viii. Water dissolves acids, bases, and salts
1. Salts are molecules held together by ionic bonds and
disassociate into anions and cations in solution
2. Acids are molecules that release H+ ions into solution
a. The logarithm number corresponding to the
concentration of H+ ions in a liter of solution is a
measure of the acidity of a solution called pH (parts of
Hydrogen, or “power of Hydrogen”)
i. The more H+ ions present in solution the more
acidic the solution.
ii. The formula below indicates that the greater the
concentration (number of H+ ions per liter) the
lower the pH will be
pH
= log
1
[H + ]
iii. Because pH is measured in logarithm units a
change of 1 in pH equals a change of 10 X in the
number of free H+ ions.
3. Bases are molecules that remove H+ ions from solution or add
OH- to solution to form H2O which neutralizes H+
concentrations. The above formula indicates that the lower the
H+ concentration the higher the pH. The higher the pH the
more basic the solution.
4. Pure water has approximately 10-7 free dissolved H+ ions per
liter. The above formula tells us that pure water has a pH = 7
a. A pH of 7 is considered neutral
b. A pH less than 7 is acidic (pH < 7)
c. A pH greater than 7 is basic
d. Blood normal pH is 7.4 which is slightly basic but if a
patient has a blood pH of 7.2 (still slightly basic) they
are said to be acidotic or in a state of acidosis.
ix. Ways of expressing the concentration of a solute in water.
1. as a percentage. Example drugstore Hydrogen peroxide (H2O2)
is usually 3% Hydrogen Peroxide.
2. or by moles per liter. Or molar concentration.
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Chapt 2 Notes
Chemical Organization of the Body
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a. A mole of a substance is the weight in grams equal to
the atomic mass of a molecule of a substance.
b. Example: from the periodic table Sodium has an atomic
mass of 23 and Chlorine has a mass of 35. Therefore,
NaCl has an atomic mass of 58. to measure out one mole
of NaCl you would weigh 58 grams.
c. A mole of any substance always provides Avogadro’s
number of molecules of that substance regardless of the
weight required to achieve a mole. (Avogadro’s number
= 6.023 x 1023)
c. Many different organic molecules contain the same carbon chain or rings,
but have different functional side groups. The carbon group is often called
the carbon skeleton for the molecule.