© 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey Chapter 2 Biochemistry for Biology

Figure 2.00 Fluoride in water Is a common ingredient in Earth’s crust Helps maintain healthy teeth

© 2010 Pearson Education, Inc. Fluoride prevents cavities by –Affecting the metabolism of oral bacteria –Promoting the replacement of lost minerals on the tooth surface

© 2010 Pearson Education, Inc. Matter: Elements and Compounds Matter is anything that occupies space and has mass. Matter is found on the Earth in three physical states: –Solid –Liquid –Gas

© 2010 Pearson Education, Inc. Matter is composed of chemical elements. –Elements are substances that cannot be broken down into other substances. –There are 92 naturally occurring elements on Earth. All of the elements are listed in the periodic table.

© 2010 Pearson Education, Inc. Periodic Table

Mercury  Hg  Figure 2.1a

Copper  Cu  Figure 2.1b

Lead  Pb  Figure 2.1c

© 2010 Pearson Education, Inc. Twenty-five elements are essential to life. Four elements make up about 96% of the weight of the human body: –Oxygen –Carbon –Hydrogen –Nitrogen

© 2010 Pearson Education, Inc. Trace elements –Occur in smaller amounts –Are essential for life An iodine deficiency causes goiter (an enlargement of the thyroid gland).

Figure 2.3

© 2010 Pearson Education, Inc. Elements can combine to form compounds. –Compounds are substances that contain two or more elements. –Common compounds include –NaCl (table salt) –H 2 O (water)

© 2010 Pearson Education, Inc. Atom Subatomic particles found in atoms

Nucleus Protons Neutrons Electrons Nucleus Cloud of negative charge  2 electrons  Figure 2.4

© 2010 Pearson Education, Inc. Atoms atomic number mass number

© 2010 Pearson Education, Inc.  H (hydrogen) atomic # = 1 mass # = 1  He (helium) atomic # = 2 mass # = 4

© 2010 Pearson Education, Inc.  Isotope  Radioisotope  Half- life

Electron Arrangement and the Chemical Properties of Atoms Electrons determine how an atom behaves when it encounters other atoms. Electrons orbit the nucleus of an atom in specific electron shells. The number of electrons in the outermost shell determines the chemical properties of an atom. © 2010 Pearson Education, Inc.

Rules of electrons

First electron shell  can hold 2 electrons  Outer electron shell  can hold 8 electrons  Hydrogen  H  Atomic number = 1 Carbon  C  Atomic number = 6 Nitrogen  N  Atomic number = 7 Oxygen  O  Atomic number = 8 Electron Figure 2.5

© 2010 Pearson Education, Inc. Animation 2-1  molecules

© 2010 Pearson Education, Inc. Types of bonds 1. Ionic bonds - Ion

Outer shell has 1 electron Outer shell has 7 electrons The outer electron is stripped from sodium and completes the chlorine atom’s outer shell Na Sodium atom Cl Chlorine atom Figure 2.6-1

Outer shell has 1 electron Outer shell has 7 electrons The outer electron is stripped from sodium and completes the chlorine atom’s outer shell Na Sodium atom Cl Chlorine atom Complete outer shells The attraction between the ions—an ionic bond—holds them together Na  Sodium ion Cl  Chlorine ion Sodium chloride (NaCl) Figure 2.6-2

© 2010 Pearson Education, Inc. 2. Covalent bond

Name  molecular formula  Hydrogen gas  H 2  Oxygen gas  O 2  Methane  CH 4  Electron configurationStructural formulaSpace-filling modelBall-and-stick model Single bond  a pair of shared electrons  Double bond  two pairs of shared electrons  Figure 2.7

© 2010 Pearson Education, Inc. Types of covalent bonds a. nonpolar bond b. polar bond

© 2010 Pearson Education, Inc. Polar Bonds Water is a compound in which the electrons in its covalent bonds are not shared equally. –This causes water to be a polar molecule, one with opposite charges on opposite ends.

HH O  slightly   slightly –  Figure UN2-2

© 2010 Pearson Education, Inc. Chemical Reactions Cells constantly rearrange molecules by breaking existing chemical bonds and forming new ones. –Such changes in the chemical composition of matter are called chemical reactions.

2 H 2 2 H 2 O O2O2 Hydrogen gas Oxygen gas Water ProductsReactants   Figure UN2-3

© 2010 Pearson Education, Inc. The polarity of water results in weak electrical attractions between neighboring water molecules.

© 2010 Pearson Education, Inc. 3. Hydrogen bond

Hydrogen bond Figure 2.8

© 2010 Pearson Education, Inc. Water’s Life-Supporting Properties 1. Cohesion- water molecules stick together 2. Water has a strong resistance to change in temperature. 3. Frozen water floats. 4. Water is a common solvent for life.

© 2010 Pearson Education, Inc. Water molecules stick together

Microscopic tubes Cohesion due to hydrogen bonds between water molecules Evaporation from the leaves SEM Flow of water Figure 2.10 Cohesion

Figure 2.11

© 2010 Pearson Education, Inc. Animation 3-1  properties of water

Hydrogen bond Liquid water Ice Figure 2.13 Ice is less dense than water

© 2010 Pearson Education, Inc. Acids, bases and salts  Solvent  Solute  Acid  Base  Salts

© 2010 Pearson Education, Inc.