BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections CHAPTER 3 The Molecules of Cells Modules 3.1 – 3.3

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Life’s diversity results from the variety of molecules in cells A spider’s web-building skill depends on its DNA molecules DNA also determines the structure of silk proteins –These make a spider web strong and resilient –Spider silk is an extremely strong material and is on weight basis stronger than steel. It has been suggested that a pencil thick strand of silk could stop a Boeing 747 in flight. Spider Silk: Stronger than Steel

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The capture strand contains a single coiled silk fiber coated with a sticky fluid The coiled fiber unwinds to capture prey and then recoils rapidly. The spider can easily recycle the silk by eating it. The web is easily destroyed by bad weather and by catching prey. After a day or two the adhesive droplets of glue also lose their adhesiveness. The old web is eaten and a new web is constructed again. The cutting and the digesting of the web are done by special digestive juices that contain enzymes rather than by any mechanical cutting. These juices are also used to connect the strands of silk together. Coiled fiber of silk protein Coating of capture strand

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Life’s structural and functional diversity results from a great variety of molecules Over 2 million organic molecules are known. A relatively small number of structural patterns underlies life’s molecular diversity INTRODUCTION TO ORGANIC COMPOUNDS AND THEIR POLYMERS

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A carbon atom forms four covalent bonds –It can join with other carbon atoms to make straight chains, branched chains or rings 3.1 Life’s molecular diversity is based on the properties of carbon Figure 3.1, top part Structural formula Ball-and-stick model Space-filling model Methane The 4 single bonds of carbon point to the corners of a tetrahedron.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Carbon skeletons vary in many ways EthanePropane Carbon skeletons vary in length. ButaneIsobutane Skeletons may be unbranched or branched. 1-Butene2-Butene Skeletons may have double bonds, which can vary in location. CyclohexaneBenzene Skeletons may be arranged in rings. Figure 3.1, bottom part

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Functional groups are the groups of atoms that participate in chemical reactions –Hydroxyl groups (OH) are characteristic of alcohols. ex ethanol –The carboxyl group (COOH) acts as an acid. ex acetic acid or vinegar –The carbonyl group (C=O). Ex. Sugars typically have a hydroxyl and carbonyl group –An amino group (NH2) ex. Amino acids contain both an amino group and a carboxyl group –A phosphate group (OPO3 -2 ) is typically involved in energy transfer. 3.2 Functional groups help determine the properties of organic compounds

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Table 3.2

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Most of the large molecules in living things are macromolecules called polymers –Polymers are long chains of smaller molecular units called monomers –A huge number of different polymers can be made from a small number of monomers –Linked polymers form macromolecules 3.3 Cells make a huge number of large molecules from a small set of small molecules

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cells link monomers to form polymers by dehydration synthesis 123 Unlinked monomer Removal of water molecule 1234 Longer polymer Figure 3.3A Short polymer

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Polymers are broken down to monomers by the reverse process, hydrolysis Coating of capture strand 123 Addition of water molecule 123 Figure 3.3B 4