Biochemistry: A Short Course Third Edition

Book Preface

As humans, we are adept learning machines. Long before a baby learns that she can change a sheet of paper by crumpling it, she is absorbing vast amounts of information. This learning continues throughout life in myriad ways: learning to ride a bike and to take social cues from friends; learning to drive a car and balance a checkbook; learning to solve a quadratic equation and to interpret a work of art.

Of course, much of learning is necessary for survival, and even the simplest organisms learn to avoid danger and recognize food. However, humans are especially gifted in that we also acquire skills and knowledge to make our lives richer and more meaningful. Many students would agree that reading novels and watching movies enhance the quality of our lives because we can expand our horizons by vicariously being in situations we would never experience, reacting sympathetically or unsympathetically to characters who remind us of ourselves or are very different from anyone we have ever known. Strangely, at least to us as science professors, science courses are rarely thought of as being enriching or insightful into the human condition. Larry Gould, a former president of Carleton College, was also a geologist and an Arctic explorer. As a scientist, teacher, and administrator, he was very interested in science education especially as it related to other disciplines. In his inaugural address when he became president he said, “Science is a part of the same whole as philosophy and the other fields of learning. They are not mutually exclusive disciplines but they are independent and overlapping.” Our goal was to write a book that encourages students to appreciate biochemistry in this broader sense, as a way to enrich their understanding of the world.

The ultimate goal of all scientific endeavors is to develop a deeper, richer understanding of ourselves and the world in which we live. Biochemistry has had and will continue to have an extensive role in helping us to develop this understanding. Biochemistry, the study of living organisms at the molecular level, has shown us many of the details of the most fundamental processes of life. For instance, biochemistry has shown us how information flows from genes to molecules that have functional capabilities. In recent years, biochemistry has also unraveled some of the mysteries of the molecular generators that provide the energy that powers living organisms. The realization that we can understand such essential life processes has significant philosophical implications. What does it mean, biochemically, to be human? What are the biochemical differences between a human being, a chimpanzee, a mouse, and a fruit fly? Are we more similar than we are different?

The understanding achieved through biochemistry is greatly influencing medicine and other fields. Although we may not be accustomed to thinking of illness in relation to molecules, illness is ultimately some sort of malfunction at the molecular level. The molecular lesions causing sickle-cell anemia, cystic fibrosis, hemophilia, and many other genetic diseases have been elucidated at the biochemical level. Biochemistry is also contributing richly to clinical diagnostics. For example, elevated levels of heart enzymes in the blood reveal whether a patient has recently had a myocardial infarction (heart attack). Agriculture, too, is employing biochemistry to develop more effective, environmentally safer herbicides and pesticides and to create genetically engineered plants that are, for example, more resistant to insects.

In this section, we will learn some of the key concepts that structure the study of biochemistry. We begin with an introduction to the molecules of biochemistry, followed by an overview of the fundamental unit of biochemistry and life itself—the cell. Finally, we examine the weak reversible bonds that enable the formation of biological structures and permit the interplay between molecules that makes life possible

✓ By the end of this section, you should be able to:

1 Describe the key classes of biomolecules and differentiate between them.
✓ 2 List the steps of the central dogma.
✓ 3 Identify the key features that differentiate eukaryotic cells from prokaryotic cells.
✓ 4 Describe the chemical properties of water and explain how water affects biochemical interactions.
✓ 5 Describe the types of noncovalent, reversible interactions and explain why reversible interactions are important in biochemistry.
✓ 6 Define pH and explain why changes in pH may affect biochemical systems