Foundation in Microbiology 5ed

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PowerPoint®
Lecture Slide Presentation prepared by Christine L. Case
M I C R O B I O L O G Y
a n i n t r o d u c t i o n
ninth edition TORTORA  FUNKE  CASE
Part A2
Chemical
Principles

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 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.
Chemistry

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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.
Figure 2.1

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16
8 O 17
8 O 18
8 O
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:

6. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 2.1

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Electronic Configurations
 Electrons are arranged in electron shells corresponding
to different energy levels.

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Electronic Configurations
Table 2.2 (1 of 2)

9. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 2.2 (2 of 2)
Electronic Configurations

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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.

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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.
Figure 2.2a

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Ionic Bonds
 Ionic bonds are attractions between ions of opposite
charge. One atom loses electrons and another gains
electrons.
Figure 2.2b

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Covalent Bonds
 Covalent bonds form when two atoms share one or
more pairs of electrons.
Figure 2.3a

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Hydrogen Bonds
 Hydrogen bonds form when a
hydrogen atom covalently
bonded to an O or N atom in
another molecule.
Figure 2.4

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H2O
2H = 2 × 1 = 2
O = 16
MW = 18
1 mole weighs 18g
Molecular Weight and Moles
 The sum of the atomic
weights in a molecule is
the molecular weight.
 One mole of a substance
is its molecular weight in
grams.

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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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 Occur when atoms, ions, or molecules combine
to form new, larger molecules.
 Anabolism is the synthesis of molecules in a cell.
Synthesis Reactions
A + B AB
Atom, ion,
or molecule A
→
Atom, ion,
or molecule B
New molecule
AB
Combines
to form

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 Occur when a molecule is split into smaller molecules,
ions, or atoms.
 Catabolism is the decomposition reactions in a cell.
A + BAB
Atom, ion,
or molecule A
→
Atom, ion,
or molecule B
New molecule
AB
Breaks
down into
Decomposition Reactions

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NaCl + H2ONaOH + HCl →
Exchange Reactions
 Are part synthesis and part decomposition.

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 Can readily go in either direction.
 Each direction may need special conditions.
A + B
Water
←
→ AB
Heat
Reversible Reactions