Lecture Presentations by Carol R. Anderson Westwood College, River Oaks Campus © 2014 Pearson Education, Inc. BIOLOGY Life on Earth WITH PHYSIOLOGY Tenth Edition Audesirk Audesirk Byers 3 Biological Molecules

© 2014 Pearson Education, Inc. Chapter 3 At a Glance  3.1 Why Is Carbon So Important in Biological Molecules?  3.2 How Are Organic Molecules Synthesized?

© 2014 Pearson Education, Inc. 3.1 Why Is Carbon So Important in Biological Molecules?  Organic refers to molecules containing a carbon skeleton bonded to hydrogen atoms  Inorganic refers to carbon dioxide and all molecules without carbon

© 2014 Pearson Education, Inc. 3.1 Why Is Carbon So Important in Biological Molecules?  The unique bonding properties of carbon are key to the complexity of organic molecules –The carbon atom is versatile because it has four electrons in an outermost shell that can accommodate eight electrons –Therefore, a carbon atom can become stable by forming up to four bonds (single, double, or triple) –As a result, organic molecules can assume complex shapes, including branched chains, rings, sheets, and helices

© 2014 Pearson Education, Inc. Figure 3-1 Bonding patterns hydrogen C carbon nitrogen oxygen CC C N OO NN H

© 2014 Pearson Education, Inc. 3.1 Why Is Carbon So Important in Biological Molecules?  The unique bonding properties of carbon are key to the complexity of organic molecules (continued) –Functional groups in organic molecules determine the characteristics and chemical reactivity of the molecules –Functional groups are less stable than the carbon backbone and are more likely to participate in chemical reactions

© 2014 Pearson Education, Inc. Table 3-1

© 2014 Pearson Education, Inc. 3.2 How Are Organic Molecules Synthesized?  Small organic molecules (called monomers) are joined to form longer molecules (called polymers)  Biomolecules are joined or broken through dehydration synthesis or hydrolysis

© 2014 Pearson Education, Inc. 3.2 How Are Organic Molecules Synthesized?  Biological polymers are formed by removing water and split apart by adding water –Monomers are joined together through dehydration synthesis, at the site where an H and an OH are removed, resulting in the loss of a water molecule (H 2 O) –The openings in the outer electron shells of the two subunits are filled when the two subunits share electrons, creating a covalent bond

© 2014 Pearson Education, Inc. Figure 3-2 Dehydration synthesis dehydration synthesis

© 2014 Pearson Education, Inc. 3.2 How Are Organic Molecules Synthesized?  Biological polymers are formed by removing water and split apart by adding water (continued) –Polymers are broken apart through hydrolysis (“water cutting”) –Water is broken into H and OH and is used to break the bond between monomers

© 2014 Pearson Education, Inc. Animation: Dehydration Synthesis and Hydrolysis

© 2014 Pearson Education, Inc. Figure 3-3 Hydrolysis hydrolysis

© 2014 Pearson Education, Inc. 3.2 How Are Organic Molecules Synthesized?  Biological polymers are formed by removing water and split apart by adding water (continued) –All biological molecules fall into one of four categories –Carbohydrates –Lipids –Proteins –Nucleotides/nucleic acids

© 2014 Pearson Education, Inc. Table 3-2