Lecture PowerPoint to accompany
Foundations in
Microbiology
Seventh Edition
Talaro
Chapter 2
The Chemistry of
Biology
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2.1 Atoms, Bonds, and Molecules
• Matter - all materials that occupy space and have
mass
• Matter is composed of atoms
• Atom - simplest form of matter not divisible into
simpler substances
– Protons: (+) subatomic particles
– Neutrons: neutral subatomic particles
– Electrons: (-) subatomic particles
2
Figure 2.1a Three-dimensional model
3
Figure 2.1b Simple model
4
Different Types of Atoms
• All atoms share the same fundamental structure
• Element - pure substances with a characteristic
number of protons, neutrons, and electrons and
predictable chemical behaviors
5
Table 2.1 The Major Elements of Life
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Characteristics of Elements
Atomic number – number of protons
Mass number – number of protons and neutrons
Isotopes – variant forms of the same element that differ
in the number of neutrons
Atomic weight – average mass numbers of all isotopic
forms
Electron orbitals – volumes of space surrounding the
atomic nucleus where electrons are likely to be found
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Figure 2.1 Models of atomic structure
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Figure 2.2 Biologically important atoms
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Bonds and Molecules
• Molecule - a chemical substance that results from the
combination of two or more atoms
• Compounds - molecules that are combinations of two
or more different elements
• Formula/Mass weight - sum of all of the atomic
masses of the atoms a molecule contains
• Chemical bonds - when 2 or more atoms share,
donate, or accept electrons to form molecules and
compounds
– 3 types: covalent, ionic, and hydrogen
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3 Types of Chemical Bonds
1. Covalent bonds – electrons are shared among
atoms
–
–
Polar covalent bonds – unequal sharing
Nonpolar covalent bonds – equal sharing
2. Ionic bonds – electrons are transferred to one
atom forming positively charged cations and
negatively charged anions
3. Hydrogen bonds – weak bonds between
hydrogen and other atoms
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Figure 2.3 Three types of bonds
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Figure 2.4 Covalent bonds
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Figure 2.5 Polar molecule
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Figure 2.6 Ionic bonding
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Figure 2.7 Ionization
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Figure 2.8 Hydrogen bonding
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Electron Transfer and OxidationReduction Reactions
Energy exchange in cells is a result of the
movement of electrons from one molecule to
another.
Oxidation – the loss of electrons
Reduction – the gaining of electrons
Redox reactions – essential to biochemical
processes
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Figure 2.9 Oxidation-reduction reaction
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Chemical Shorthand
• Reactants - molecules starting a reaction
• Products - substances left by a reaction
• Synthesis reaction - the reactants bond
together in a manner that produces an entirely
new molecule
S + O2
SO2
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Figure 2.10 Molecular and Structural Formulas
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Solutions: Mixtures of Molecules
Solution – a mixture of one or more substances called
solutes, dispersed in a dissolving medium called a
solvent
Solutes –
Na+
-
& Cl
Solvent – H2O
22
• Most biological activities occur in aqueous
(water-based) solutions
• Hydrophilic molecules - dissolve in water
• Hydrophobic molecules - repel water
• Amphipathic molecules - have both
hydrophilic and hydrophobic properties
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Figure 2.12 Hydration spheres formed around ions
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Acidity, Alkalinity, and the pH Scale
•Ionization of H2O releases hydrogen ions
+
[H ] and hydroxyl ions [OH ]
•pH scale – ranges from 0 to 14, expresses
the concentration of H+ ions
•pH is the negative logarithm of the
concentration of H+ ions.
•pH 2 = 0.01 moles/L H+ ions
•pH 14 = 0.00000000000001 moles/L H+ ions
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Figure 2.13 The pH scale
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Table 2.2
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The Chemistry of Carbon and
Organic Compounds
• Organic chemicals – compounds
containing carbon bonded to hydrogens
28
• Carbon is the fundamental element of life
– Contains 4 atoms in its outer orbital
– Can form single, double, or triple covalent bonds
– Can form linear, branched, or ringed molecules
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Figure 2.14 The versatility of bonding in carbon
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Functional Groups of Organic Compounds
• Accessory molecules
that bind to organic
compounds
• Confer unique reactive
properties on the whole
molecule
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2.2 Macromolecules
• Biochemicals are organic compounds
produced by living things
• Macromolecules: large compounds assembled
from smaller subunits
– Monomer: a repeating subunit
– Polymer: a chain of monomers
32
Macromolecules
1. Carbohydrates – monosaccharides, disaccharides,
polysaccharides
2. Lipids – triglycerides (fats and oils), phospholipids,
steroids
3. Proteins
4. Nucleic acids – DNA, RNA
33
Carbohydrates
• Sugars and polysaccharides
• General formula (CH2O)n
• Aldehydes and ketones
• Saccharide: simple carbohydrate
– Monosaccharide: 3-7 carbons
– Disaccharide: two monosaccharides
– Polysaccharide: five or more monosaccharides
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Figure 2.15a Common classes of carbohydrates
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Figure 2.15b Common classes of carbohydrates
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Carbohydrates
• Subunits linked by glycosidic bonds
• Dehydration synthesis: loss of water in a
polymerization reaction
37
Carbohydrates
• Functions – cell structure, adhesion, and metabolism
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Lipids
• Long or complex, hydrophobic, C - H chains
• Triglycerides, phospholipids in membranes,
steroids like cholesterol
• Functions
– Triglycerides – energy storage
– Phospholipid – major cell membrane component
– Steroids – cell membrane component
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Figure 2.18b Triglycerides
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Figure 2.19 Phospholipids - membrane molecules
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Figure 2.20 Membrane
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Proteins
•
•
•
•
•
•
Predominant molecules in cells
Monomer – amino acids – 20
Polymer – peptide, polypeptide, protein
Subunits linked by peptide bonds
Fold into very specific 3-D shapes
Functions – support, enzymes, transport,
defense, movement
43
44
Figure 2.21 Formation of a peptide bond
45
46
Nucleic Acids
• DNA and RNA
• Monomer – nucleotide
• DNA – deoxyribonucleic acid
– A,T,C,G – nitrogen bases
– Double helix
– Function – hereditary material
• RNA – ribonucleic acid
– A,U,C,G – nitrogen bases
– Function – organize protein synthesis
47
48
Figure 2.24 Sugars and nitrogen bases of DNA and RNA
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Double Helix of DNA
• DNA is formed by two very
long polynucleotide strands
linked along their length by
hydrogen bonds
50
Passing on the Genetic Message
• Each strand is copied
• Replication is guided by
base pairing
• End result is two
separate double strands
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ATP: The Energy Molecule of Cells
• Adenosine triphosphate
– Nucleotide - adenine, ribose, three phosphates
• Function - transfer and storage of energy
Insert figure 2.27 a
ATP molecule
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