1. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint ® Lecture Slides for Essential Biology, Second Edition & Essential Biology with Physiology Neil Campbell, Jane Reece, and Eric Simon Presentation prepared by Chris C. Romero CHAPTER 3 The Molecules of Life Figures 3.16 – 3.20

2. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Steroids are very different from fats in structure and function Steroids –The carbon skeleton is bent to form four fused rings Cholesterol is the base steroid from which your body produces other steroids –Example: sex hormones Figure 3.16 Cholesterol TestosteroneA type of estrogen

3. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Synthetic anabolic steroids are controversial –They are variants of testosterone –Some athletes use them to build up their muscles quickly –They can pose serious health risks Figure 3.17

4. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings A protein is a polymer constructed from amino acid monomers Proteins Proteins perform most of the tasks the body needs to function –They are the most elaborate of lifes molecules

5. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The four types of proteins Figure 3.18 (a) Structural proteins (b) Storage proteins (c) Contractile proteins (d) Transport proteins

6. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings All proteins are constructed from a common set of 20 kinds of amino acids The Monomers: Amino Acids

7. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Each amino acid consists of –A central carbon atom bonded to four covalent partners –A side group that is variable among all 20 Figure 3.19 Amino group Carboxyl group Side group (a) Side groups (b) Leucine Serine (hydrophobic)

8. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Carboxyl group Amino group Side group Side group Amino acid Dehydration synthesis Side group Side group Peptide bond Cells link amino acids together by dehydration synthesis Proteins as Polymers –The resulting bond between them is called a peptide bond Figure 3.20

9. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Your body has tens of thousands of different kinds of protein –The arrangement of amino acids makes each one different