PowerPoint Lecture Presentations prepared by Mindy Miller-Kittrell, North Carolina State University C H A P T E R 2 The Chemistry of Microbiology
Atoms Matter anything that takes up space and has mass Atoms the smallest chemical units of matter
Atoms Atomic Structure Electrons negatively charged subatomic particles circling a nucleus Nucleus structure containing neutrons and protons Neutrons uncharged particles Protons positively charged particles
Figure 2.1 An example of a Bohr model of atomic structure.
Atoms Atomic Structure Element composed of a single type of atom Atomic number equal to the number of protons in the nucleus Atomic mass (atomic weight) sum of masses of protons, neutrons, and electrons
Table 2.1 Common Elements of Life
Atoms Isotopes Atoms of a given element that differ in the number of neutrons in their nuclei Stable isotopes Unstable isotopes Radioactive isotopes Release energy during radioactive decay
Figure 2.2 Nuclei of the three naturally occurring isotopes of carbon.
Atoms Electron Configurations Only the electrons of atoms interact, so they determine atom s chemical behavior. Electrons occupy electron shells. Valence electrons electrons in outermost shell that interact with other atoms
Figure 2.3 Electron configurations.
Figure 2.4 Bohr diagrams of the first 20 elements and their places within the chart known as the periodic table of the elements.
Atoms Tell Me Why Electrons zip around the nucleus at about 5 million miles per hour. Why don t they fly off?
Chemical Bonds Valence combining capacity of an atom Positive if atom has electrons to give up Negative if atom has spaces to fill Stable when outer electron shells contain eight electrons Chemical bonds atoms combine by sharing or transferring valence electrons Molecule two or more atoms held together by chemical bonds Compound a molecule composed of more than one element
Chemical Bonds Covalent bond sharing of a pair of electrons by two atoms Electronegativity attraction of atom for electrons The more electronegative an atom, the greater the pull its nucleus exerts on electrons.
Figure 2.6 Electronegativity values of selected elements.
Chemical Bonds Nonpolar Covalent Bonds Shared electrons spend equal amounts of time around each nucleus. Atoms with similar electronegativities No poles exist. Carbon atoms form four nonpolar covalent bonds with other atoms. Organic compounds contain carbon and hydrogen atoms.
Figure 2.5a-b Four molecules formed by covalent bonds.
Figure 2.5c-d Four molecules formed by covalent bonds.
Chemical Bonds Polar Covalent Bonds Unequal sharing of electrons due to significantly different electronegativities Most important polar covalent bonds involve hydrogen. Allow for hydrogen bonding
Figure 2.7 Polar covalent bonding in a water molecule.
Chemical Bonds Ionic Bonds Occur when two atoms with vastly different electronegativities come together Atoms have either positive (cation) or negative (anion) charges. Cations and anions attract each other and form ionic bonds (no electrons shared). Typically form crystalline ionic compounds known as salts
Figure 2.8 The interaction of sodium and chlorine to form an ionic bond.
Figure 2.9 Dissociation of NaCl in water.
Chemical Bonds Hydrogen Bonds Electrical attraction between partially charged H + and full or partial negative charge on same or different molecule Weaker than covalent bonds but essential for life Help to stabilize 3-D shapes of large molecules
Figure 2.10 Hydrogen bonds.
Table 2.2 Characteristics of Chemical Bonds
Chemical Bonds Tell Me Why Chlorine and potassium atoms form ionic bonds, carbon atoms form nonpolar covalent bonds with nitrogen atoms, and oxygen forms polar covalent bonds with phosphorus. Explain why these bonds are the types they are.
Chemical Reactions The making or breaking of chemical bonds Involve reactants and products Biochemistry involves chemical reactions of living things.
Chemical Reactions Synthesis Reactions Involve the formation of larger, more complex molecules Require energy (endothermic) Common type is dehydration synthesis Water molecule formed All the synthesis reactions in an organism are called anabolism.
Figure 2.11a Two types of chemical reactions in living things.
Chemical Reactions Decomposition Reactions Break bonds within larger molecules to form smaller atoms, ions, and molecules Release energy (exothermic) Common type is hydrolysis Ionic components of water are added to products. All the decomposition reactions in an organism are called catabolism.
Figure 2.11b Two types of chemical reactions in living things.
Chemical Reactions Exchange Reactions Involve breaking and forming covalent bonds Have endothermic and exothermic steps Involve atoms moving from one molecule to another Sum of all chemical reactions in an organism is called metabolism.
Chemical Reactions Tell Me Why Why are decomposition reactions exothermic, that is, energy releasing?
Water, Acids, Bases, and Salts Water Most abundant substance in organisms Many special characteristics due to two polar covalent bonds: Cohesive molecules generate surface tension Excellent solvent Remains liquid across wide range of temperatures Can absorb significant amounts of heat energy without changing temperature Participates in many chemical reactions
Figure 2.12 The cohesiveness of liquid water.
Water, Acids, Bases, and Salts Acids and Bases Dissociated by water into component cations and anions Acid dissociates into one or more H + and one or more anions Base binds with H + when dissolved in water; some dissociate into cations and OH Concentration of H + in solution expressed using the ph scale
Figure 2.13 Acids and bases.
Figure 2.14 The ph scale.
Water, Acids, Bases, and Salts Acids and Bases Metabolism requires relatively constant balance of acids and bases. Buffers prevent drastic changes in internal ph. Microorganisms differ in their ability to tolerate ph ranges. Some microorganisms can change the ph of their environment.
Water, Acids, Bases, and Salts Salts Compounds that dissociate in water into cations and anions other than H + and OH Cations and anions of salts are electrolytes that: Create electrical differences between inside and outside of cell Transfer electrons from one location to another Form important components of many enzymes
Water, Acids, Bases, and Salts Tell Me Why Why does the neutralization of an acid by a base often produce water?
Organic Macromolecules Functional Groups Contain carbon and hydrogen atoms Atoms often appear in arrangements called functional groups. Macromolecules large molecules used by all organisms: Lipids Carbohydrates Proteins Nucleic acids Monomers basic building blocks of macromolecules
Table 2.3 Functional Groups of Organic Molecules and Some Classes of Compounds in Which They Are Found
Organic Macromolecules Lipids Not composed of regular subunits Are all hydrophobic Four groups: Fats (triglycerides) Phospholipids Waxes Steroids
Figure 2.15 Fats (triglycerides).
Table 2.4: Common Fatty Acids in Fats and Cell Membranes
Figure 2.16 Phospholipids.
Organic Macromolecules Lipids Waxes Contain one long-chain fatty acid covalently linked to long-chain alcohol by an ester bond Lack hydrophilic head Completely insoluble in water
Figure 2.17 Steroids.
Organic Macromolecules Carbohydrates Organic molecules composed of carbon, hydrogen, and oxygen (CH 2 O) n Functions: Long-term storage of chemical energy Ready energy source Part of backbones of nucleic acids Converted to amino acids Form cell wall Involved in intracellular interactions between animal cells
Organic Macromolecules Carbohydrates Types: Monosaccharides Disaccharides Polysaccharides
Figure 2.18 Monosaccharides (simple sugars).
Figure 2.19 Disaccharides.
Figure 2.20 Polysaccharides.
Organic Macromolecules Proteins Composed mostly of carbon, hydrogen, oxygen, nitrogen, and sulfur Functions: Structure Enzymatic catalysis Regulation Transportation Defense and offense
Organic Macromolecules Proteins Amino acids The monomers that make up proteins Most organisms use only 21 amino acids in protein synthesis. Side groups affect how amino acids interact with one another and how a protein interacts with other molecules. A covalent peptide bond is formed between amino acids.
Figure 2.21 Amino acids.
Figure 2.22 Stereoisomers, molecules that are mirror images of one another.
Figure 2.23 The linkage of amino acids by peptide bonds via a dehydration reaction.
Figure 2.24 Levels of protein structure.
Organic Macromolecules Nucleotides and Nucleic Acids Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the vital genetic material of cells and viruses. RNA also acts as enzyme, binds amino acids, and helps form polypeptides.
Organic Macromolecules Nucleotides and Nucleic Acids Nucleotides and nucleosides Nucleotides Monomers that make up nucleic acids Composed of three parts: Phosphate Pentose sugar either deoxyribose or ribose One of five cyclic nitrogenous bases Nucleosides are nucleotides lacking phosphate.
Figure 2.25 Nucleotides.
Organic Macromolecules Nucleic Acids Nucleic acid structure Three H bonds form between C and G. Two H bonds form between T and A (DNA) or U and A (RNA). DNA is double stranded in most cells and viruses. The two strands are complementary. The two strands are antiparallel.
Figure 2.26 General nucleic acid structure.
Organic Macromolecules Nucleic Acids Nucleic acid function DNA is genetic material of all organisms and of many viruses. Carries instructions for synthesis of RNA and proteins Controls synthesis of all molecules in an organism Dr. Bauman s Microbiology Video Tutor For more information, listen to Dr. Bauman discuss the structure and function of nucleotides.
Table 2.5 Comparison of Nucleic Acids
Figure 2.27 ATP.
Organic Macromolecules Tell Me Why Why do the cell membranes of microbes living in Arctic water likely contain more unsaturated fatty acids than do membranes of microbes living in hot springs?