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Transcript of Foundations in Microbiology Seventh Edition Chapter 2 The Chemistry of Biology Lecture PowerPoint to...
Foundations in Microbiology
Seventh Edition
Chapter 2
The Chemistry of Biology
Lecture PowerPoint to accompany
Talaro
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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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
Figure 2.1a Three-dimensional model
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Figure 2.1b Simple model
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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
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
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
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 Oxidation-Reduction 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
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
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S O2 SO2+
Figure 2.10 Molecular and Structural Formulas
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Solutions: Mixtures of Molecules
Solutes – Na+ & Cl-
Solvent – H2O
Solution – a mixture of one or more substances called solutes, dispersed in a dissolving medium called a solvent
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• 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
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
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
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• 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
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
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Macromolecules1. Carbohydrates – monosaccharides, disaccharides,
polysaccharides
2. Lipids – triglycerides (fats and oils), phospholipids, steroids
3. Proteins 4. Nucleic acids – DNA, RNA
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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
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
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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
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
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Figure 2.21 Formation of a peptide bond
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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
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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
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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 aATP molecule