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CAMPBELL BIOLOGY Reece Urry Cain Wasserman Minorsky Jackson © 2014 Pearson Education, Inc. TENTH EDITION CAMPBELL BIOLOGY Reece Urry Cain Wasserman Minorsky Jackson TENTH EDITION 2 The Chemical Context of Life Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick
© 2014 Pearson Education, Inc. A Chemical Connection to Biology Biology is the study of life Living organisms and their environments are subject to basic laws of physics and chemistry One example is the use of formic acid by ants to protect themselves against predators and microbial parasites
© 2014 Pearson Education, Inc. Figure 2.1
© 2014 Pearson Education, Inc. Elements and Compounds Matter is made up of elements An element is a substance that cannot be broken down to other substances by chemical reactions A compound is a substance consisting of two or more elements in a fixed ratio A compound has characteristics different from those of its elements
© 2014 Pearson Education, Inc. Table 2.1
© 2014 Pearson Education, Inc. Figure 2.4 (b) (a) Electrons Nucleus Cloud of negative charge (2 electrons)
© 2014 Pearson Education, Inc. Isotopes All atoms of an element have the same number of protons but may differ in number of neutrons Isotopes are two atoms of an element that differ in number of neutrons Radioactive isotopes decay spontaneously, giving off particles and energy Radioactive isotopes are often used as diagnostic tools in medicine Radioactive tracers can be used to track atoms through metabolism They can also be used in combination with sophisticated imaging instruments
© 2014 Pearson Education, Inc. Electron Distribution and Chemical Properties The chemical behavior of an atom is determined by the distribution of electrons in electron shells The periodic table of the elements shows the electron distribution for each element
© 2014 Pearson Education, Inc. Figure 2.7 Atomic mass Atomic number Element symbol Electron distribution diagram 2 4.003 He Helium 2 He Neon 10 Ne Fluorine 9 F Oxygen 8 O Nitrogen 7 N Carbon 6 C Boron 5 B Beryllium 4 Be Lithium 3 Li Second shell First shell Hydrogen 1 H Argon 18 Ar Chlorine 17 Cl Sulfur 16 S Phosphorus 15 P Silicon 14 Si Aluminum 13 Al Magnesium 12 Mg Sodium 11 Na Third shell
© 2014 Pearson Education, Inc. Concept 2.3: The formation and function of molecules depend on chemical bonding between atoms Atoms with incomplete valence shells can share or transfer valence electrons with certain other atoms These interactions usually result in atoms staying close together, held by attractions called chemical bonds
© 2014 Pearson Education, Inc. Covalent Bonds A covalent bond is the sharing of a pair of valence electrons by two atoms In a covalent bond, the shared electrons count as part of each atom’s valence shell Hydrogen atoms (2 H) Hydrogen molecule (H 2 )
© 2014 Pearson Education, Inc. A molecule consists of two or more atoms held together by covalent bonds A compound is a combination of two or more different elements A single covalent bond, or single bond, is the sharing of one pair of valence electrons A double covalent bond, or double bond, is the sharing of two pairs of valence electrons Stronger than a single bond
© 2014 Pearson Education, Inc. Figure 2.10 Name and Molecular Formula Electron Distribution Diagram Lewis Dot Structure and Structural Formula Space- Filling Model (d) Methane (CH 4 ) (c) Water (H 2 O) (b) Oxygen (O 2 ) (a) Hydrogen (H 2 ) HH OO O H H CH H H H
© 2014 Pearson Education, Inc. Animation: Covalent Bonds
© 2014 Pearson Education, Inc. Atoms in a molecule attract electrons to varying degrees Electronegativity is an atom’s attraction for the electrons in a covalent bond The more electronegative an atom, the more strongly it pulls shared electrons toward itself
© 2014 Pearson Education, Inc. In a nonpolar covalent bond, the atoms share the electron equally In a polar covalent bond, one atom is more electronegative, and the atoms do not share the electron equally Unequal sharing of electrons causes a partial positive or negative charge for each atom or molecule
© 2014 Pearson Education, Inc. Ionic Bonds Atoms sometimes strip electrons from their bonding partners An example is the transfer of an electron from sodium to chlorine After the transfer of an electron, both atoms have charges A charged atom (or molecule) is called an ion A cation is a positively charged ion An anion is a negatively charged ion An ionic bond is an attraction between an anion and a cation
© 2014 Pearson Education, Inc. Figure 2.12-2 NaCl Na Sodium ion (a cation) Cl Chloride ion (an anion) Sodium chloride (NaCl) NaCl Na Sodium atom Cl Chlorine atom
© 2014 Pearson Education, Inc. Animation: Ionic Bonds
© 2014 Pearson Education, Inc. Weak Chemical Bonds Many large biological molecules are held in their functional form by weak bonds The reversibility of weak bonds can be an advantage A hydrogen bond forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom In living cells, the electronegative partners are usually oxygen or nitrogen atoms
© 2014 Pearson Education, Inc. Figure 2.14 Water (H 2 O) Ammonia (NH 3 ) Hydrogen bond
© 2014 Pearson Education, Inc. If electrons are distributed asymmetrically in molecules or atoms, they may accumulate by chance in one part of a molecule Van der Waals interactions are attractions between molecules that are close together as a result of these charges Collectively, such interactions can be strong, as between molecules of a gecko’s toe hairs and a wall surface
© 2014 Pearson Education, Inc. Concept 2.4: Chemical reactions make and break chemical bonds Chemical reactions are the making and breaking of chemical bonds The starting molecules of a chemical reaction are called reactants The final molecules of a chemical reaction are called products All chemical reactions are reversible: products of the forward reaction become reactants for the reverse reaction Chemical equilibrium is reached when the forward and reverse reactions occur at the same rate At equilibrium the relative concentrations of reactants and products do not change
© 2014 Pearson Education, Inc. Figure 2.UN03 ReactantsReactionProducts 2 H 2 O2O2 2 H 2 O
The Chemical Context of Life Chemical Basis of Biology.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Presentations for Biology Eighth Edition Neil Campbell.
© 2011 Pearson Education, Inc. LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman,
CAMPBELL BIOLOGY IN FOCUS © 2014 Pearson Education, Inc. Urry Cain Wasserman Minorsky Jackson Reece Lecture Presentations by Kathleen Fitzpatrick and Nicole.
The Chemical Context of Life chapter 2. 2 Energy & Matter Universe is composed of 2 things …… Universe is composed of 2 things …… Energy Energy Ability.
The chemical context of life
The Chemical Context of Life
Atom- Molecule-Element- Compound Relationship
Chapter 2 Notes The Chemical Context of Life. Concept 2.1 Organisms are composed of matter: anything that takes up space or has mass Element: a substance.
Chapter 2 The Chemical Context of Life Students get a book from the counter or from under the TV add your book number to the student info sheet turn in.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 2 The Chemical Context of Life.
Fig Fig. 2-2b Dead leaf tissue (cm 2 ) after one day Inside, unprotected Inside, protected Outside, unprotected Outside, protected Cedrela.
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