Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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 A 2 Chemical Principles

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  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

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Study of Atoms  Atoms are composed of  Electrons: Negatively charged particles  Protons: Positively charged particles  Neutrons: Uncharged particles

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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:

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

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Electronic Configurations  Electrons are arranged in electron shells corresponding to different energy levels.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Electronic Configurations Table 2.2 (1 of 2)

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

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

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings How Atoms Form Molecules: Chemical Bonds  A compound contains different kinds of atoms. H 2 O or CH 4  The forces holding atoms in a compound are chemical bonds.

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

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Ionic Bonds  Ionic bonds are attractions between ions of opposite charge. One atom loses electrons and another gains electrons. Figure 2.2b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Covalent Bonds  Covalent bonds form when two atoms share one or more pairs of electrons. Figure 2.3a

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hydrogen Bonds  Hydrogen bonds form when a hydrogen atom covalently bonded to an O or N atom in another molecule. Figure 2.4

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings H 2 O 2H = 2  1= 2 O = 16 MW=18 1 mole weighs18g 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.

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

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Occur when atoms, ions, or molecules combine to form new, larger molecules.  Anabolism is the synthesis of molecules in a cell. Synthesis Reactions A+BAB Atom, ion, or molecule A  Atom, ion, or molecule B New molecule AB Combines to form

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Occur when a molecule is split into smaller molecules, ions, or atoms.  Catabolism is the decomposition reactions in a cell. A+B AB Atom, ion, or molecule A  Atom, ion, or molecule B New molecule AB Breaks down into Decomposition Reactions

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings NaCl+H2OH2ONaOH+HCl  Exchange Reactions  Are part synthesis and part decomposition.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Can readily go in either direction.  Each direction may need special conditions. A+B Water  AB Heat Reversible Reactions