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TORTORA  FUNKE  CASE
ninth edition
MICROBIOLOGY
an introduction
2
Part A
Chemical
Principles
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Chemistry
 Chemistry is the study of interactions between atoms
and molecules.
 The atom is the smallest unit of matter that enters into
chemical reactions.
 Atoms interact to form molecules.
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The Study of Atoms
 Atoms are composed of
 Electrons: Negatively charged particles
 Protons: Positively charged particles
 Neutrons: Uncharged particles
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The Study of Atoms
 Protons and neutrons are in the nucleus.
 Electrons move around the nucleus.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 2.1
Chemical Elements
 Each chemical element has a different number of
protons.
 Isotopes of an element are atoms with different
numbers of neutrons. Isotopes of oxygen are:
16
8
O
17
8
O
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18
8
O
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Table 2.1
Electronic Configurations
 Electrons are arranged in electron shells corresponding
to different energy levels.
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Electronic Configurations
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Table 2.2 (1 of 2)
Electronic Configurations
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Table 2.2 (2 of 2)
How Atoms Form Molecules: Chemical Bonds
 Atoms combine to complete the outermost shell.
 The number of missing or extra electrons in this shell
is known as the valence.
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How Atoms Form Molecules: Chemical Bonds
 A compound contains different kinds of atoms.
H2O
 The forces holding atoms in a compound are chemical
bonds.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
How Atoms Form Molecules: Chemical Bonds
 The number of protons and electrons is equal in
an atom.
 Ions are charged atoms that have gained or lost
electrons.
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Figure 2.2a
Ionic Bonds
 Ionic bonds are attractions between ions of opposite
charge. One atom loses electrons and another gains
electrons.
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Figure 2.2b
Covalent Bonds
 Covalent bonds form when two atoms share one or
more pairs of electrons.
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Figure 2.3a
Hydrogen Bonds
 Hydrogen bonds form when a
hydrogen atom covalently
bonded to an O or N atom in
another molecule.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 2.4
Molecular Weight and Moles
 The sum of the atomic
weights in a molecule is
H2O
the molecular weight.
 One mole of a substance
2H
=21
= 2
is its molecular weight in
O
= 16
grams.
MW
= 18
1 mole weighs
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18g
Chemical Reactions
 Chemical reactions involve the making or breaking of
bonds between atoms.
 A change in chemical energy occurs during a chemical
reaction.
 Endergonic reactions absorb energy.
 Exergonic reactions release energy.
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Synthesis Reactions
 Occur when atoms, ions, or molecules combine
to form new, larger molecules.
A
Atom, ion,
or molecule A
+
B
Atom, ion,
or molecule B
Combines
to form

AB
New molecule
AB
 Anabolism is the synthesis of molecules in a cell.
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Decomposition Reactions
 Occur when a molecule is split into smaller molecules,
ions, or atoms.
AB
New molecule
AB
Breaks
down into

A
Atom, ion,
or molecule A
+
B
Atom, ion,
or molecule B
 Catabolism is the decomposition reactions in a cell.
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Exchange Reactions
 Are part synthesis and part decomposition.
NaOH +
HCl
 NaCl
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+ H2O
Reversible Reactions
 Can readily go in either direction.
 Each direction may need special conditions.
Heat
A
+ B
 AB

Water
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings