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 6
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 7
Figure 2.1 Models of atomic structure 8
Figure 2.2 Biologically important atoms 9
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 10
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 11
Figure 2.3 Three types of bonds 12
Figure 2.4 Covalent bonds 13
Figure 2.5 Polar molecule 14
Figure 2.6 Ionic bonding 15
Figure 2.7 Ionization 16
Figure 2.8 Hydrogen bonding 17
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 18
Figure 2.9 Oxidation-reduction reaction 19
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 + O 2 SO 2 20
Figure 2.10 Molecular and Structural Formulas 21
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 H 2 O 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 23
Figure 2.12 Hydration spheres formed around ions 24
Acidity, Alkalinity, and the ph Scale Ionization of H 2 O 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 25
Figure 2.13 The ph scale 26
Table 2.2 27
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 29
Figure 2.14 The versatility of bonding in carbon 30
Functional Groups of Organic Compounds Accessory molecules that bind to organic compounds Confer unique reactive properties on the whole molecule 31
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 (CH 2 O) n Aldehydes and ketones Saccharide: simple carbohydrate Monosaccharide: 3-7 carbons Disaccharide: two monosaccharides Polysaccharide: five or more monosaccharides 34
Figure 2.15a Common classes of carbohydrates 35
Figure 2.15b Common classes of carbohydrates 36
Carbohydrates Subunits linked by glycosidic bonds Dehydration synthesis: loss of water in a polymerization reaction 37
Carbohydrates Functions cell structure, adhesion, and metabolism 38
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 39
Figure 2.18b Triglycerides 40
Figure 2.19 Phospholipids - membrane molecules 41
Figure 2.20 Membrane 42
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
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Figure 2.21 Formation of a peptide bond 45
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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 47
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Figure 2.24 Sugars and nitrogen bases of DNA and RNA 49
DNA is formed by two very long polynucleotide strands linked along their length by hydrogen bonds Double Helix of DNA 50
Passing on the Genetic Message Each strand is copied Replication is guided by base pairing End result is two separate double strands 51
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 52