Biochemistry, 4th Edition P6. Continuing Garrett and Grisham's innovative conceptual and organizing framework, "Essential Questions," BIOCHEMISTRY guides students through course concepts in a way that reveals the beauty and usefulness of biochemistry in the everyday world. Streamlined for increased clarity and readability, this edition also includes new photos and illustrations that show the subject matter consistently throughout the text. New end-of-chapter problems, MCAT practice questions, and the unparalleled text/media integration with the power of CengageNOW round out this exceptional package, giving you the tools you need to both master course concepts and develop critical problem-solving skills you can draw upon. | How Do the Properties of Biomolecules Reflect Their Fitness to the Living Condition 13 TABLE Radii of the Common Atoms of Biomolecules Atom Van der Waals Radius nm Covalent Radius nm Atom Represented to Scale H C N O P S Half-thickness of an aromatic ring cific than van der Waals interactions because they require the presence of complementary hydrogen donor and acceptor groups. Ionic Interactions Ionic interactions are the result of attractive forces between oppositely charged structures such as negative carboxyl groups and positive amino groups Figure . These electrostatic forces average about 20 kJ mol in aqueous solutions. Typically the electrical charge is radially distributed so these interactions may lack the directionality of hydrogen bonds or the precise fit of van der Waals interactions. Nevertheless because the opposite charges are restricted to ster-ically defined positions ionic interactions can impart a high degree of structural specificity. The strength of electrostatic interactions is highly dependent on the nature of the interacting species and the distance r between them. Electrostatic interactions may involve ions species possessing discrete charges permanent dipoles having a permanent separation of positive and negative charge or induced dipoles having a temporary separation of positive and negative charge induced by the environment . Hydrophobic Interactions Hydrophobic interactions result from the strong tendency of water to exclude nonpolar groups or molecules see Chapter 2 . Hydrophobic interactions arise not so much because of any intrinsic affinity of nonpolar substances for one another although van der Waals forces do promote the weak bonding of nonpolar substances but because water molecules prefer the stronger interactions that they share with one another compared to their interaction with nonpolar molecules. Hydrogen-bonding interactions between polar .
