Principles of Cell Biology 3rd Edition

Book Preface

As the rate of discovering facts in the sciences continues to escalate, both students and instructors must confront the age-old problem of deciding what material matters most,especially at the introductory level. In our experience, even the most enthusiastic students have great difficulty distinguishing essential facts in cell biology from more technical details. Given the heavy emphasis on memorization in most K–12 programs, many introductory-level college students resort to storing as much information as possible in short-term memory, only to discover later that they’ve missed the underlying concepts that give these facts their significance. In the past 25 years of teaching, we have spent as much time helping students navigate a conceptual path through the dense web of facts in cell biology as we have explaining the meaning of those facts.
The purpose of this book is to help students build a conceptual framework for cell biology that will persist long after their coursework is complete.

Our Approach to Learning Cell Biology

The field of introductory cell biology enjoys a wealth of well-written texts by outstanding authors. Why add yet another introductory text? This book is needed for two important reasons. First, it overtly focuses on some of the underlying principles that illustrate both how cells function as well as how we study them. While many textbooks reference “principles” in their fields, few specifically identify these principles or explore them in detail. In contrast, this book identifies 14 specific principles of cell biology (see page xiv), and devotes a separate chapter to illustrate each one of them.
As a result:

■ We intentionally shift away from the traditional focus on technical details and toward a more integrative view of cellular activity that can be tailored to suit students with a broad range of backgrounds.
■ Instructors have great freedom to organize technical subjects as they see fit while permitting students to build their own conceptual view of how cells solve problems. In short, because every cellular activity discussed in the text is tied directly to an overlying principle, these activities can be arranged and taught in many different combinations, at varying depths of detail, without losing focus on the Big Picture.
■ Students develop a framework for evaluating facts as they encounter them, and this invites them to critically evaluate information as they learn. The principles in this book are not intended to be treated as laws and are thus always subject to criticism and review.
■ Instructors can capitalize on this organizing style to seamlessly merge supplemental material with the text as the field changes or to emphasize specific subjects in a topics course.
■ Professionals in the field can use these principles as starting points for identifying additional principles in cell biology and in other related fields, for comparing these principles in other fields of biology, and for developing a more integrated curriculum across multiple scales of biological organization. For example, mapping several courses to specific principles such as those identified in this text could assist in curriculum development and assessment at a department or program administrative level.

The second important distinguishing feature of this book is its informal, narrative writing style. We adopted this style to make even the most complex concepts accessible to students new to a scientific field, including stripping away some of the technical complexity that many introductory students find intimidating. Each chapter thus reflects our own lectures in introductory cell biology, in both style and content. Specifically, this includes:

■ Liberal use of analogies that have proven effective over many years of teaching
■ Boxes throughout each chapter including studying tips, clarifications of apparent contradictions, explanations of naming schemes, FAQs, etc.
■ Gradual introduction of jargon, after the concepts have been established, thereby de-emphasizing memorization of names
■ Novel artwork reflecting drawing exercises the authors include in their own lectures

Audience

Principles of Cell Biology is written for introductory cell biology courses having an emphasis on eukaryotic cells, especially humans and other mammals. It is geared toward students in general biology, molecular biology, physiology, nursing, dental hygiene, and bioengineering. The book also provides a firm foundation for advanced programs in biological sciences, medicine, dentistry, and bioengineering.

Organization

The book consists of four chapters (1–4) that introduce the fundamental molecular building blocks of all cells: sugars, proteins, nucleic acids, and lipids. Chapter 1 also firmly establishes the role of natural selection as a driving force in the evolution of life at the level of single cells. The remaining 10 chapters focus on illustrating how cells use these building blocks to perform their essential functions. We do not assume students must read the chapters in order; instructors should be able to arrange the chapters in any sequence with minimal impact on topic continuity.
Some chapters can be clustered into broader themes. Chapters 5 and 6 focus on the cytoskeleton and extracellular matrix, respectively, to explain how cells establish, maintain, and modify their shapes. Chapters 7–9 focus on DNA replication, transcription, translation, protein sorting, and the endomembrane system to illustrate the theme of information transfer from DNA to proteins. Chapters 11–13 use signal transduction as a unifying theme to illustrate the relationships among signaling pathways, control of gene expression, and cell growth/apoptosis. Finally, Chapter 14 revisits the evolution theme in Chapter 1 but updates it to include artificial selection by humans as the next paradigm shift in evolution. This allows students to review the technology topics presented in Chapters 1-13 in the context of creating new forms of life.

What’s New

First and foremost, we added a new author, Dr. Diana Bebek Ivankovic. Dr. Ivankovic has over 25 years of teaching and research experience in cell biology, cancer, genetics, and microbiology as well as years of experience as a textbook editor, reviewer, and contributor. She is the source and inspiration of the new pedagogic elements in the third edition.
We received over 250 comments/suggestions on the second edition from students, instructors, and subject matter experts, adjudicated each, and incorporated most them into the third edition. For example, we added five new elements to every chapter:

■ First, we addressed reviewers’ requests for more emphasis on cell biology techniques by adding “Applied Cell Biology” callout boxes that discuss technology in the context of each chapter’s principle.
■ Second, we added a “Case Study” to each chapter to illustrate how the concepts of the chapter apply to modern challenges in biology; these focus primarily on human health and disease, reflecting our emphasis on eukaryotic organisms. The case studies also include study questions, with suggested answers provided in the back matter of the text.
■ Third, we embraced the wealth of content available on the World Wide Web by providing sample search terms and inviting students to explore the chapter topics online.
■ Fourth, for the eBook version, we provide online access to one video lesson, recorded by Dr. Ivankovic, for each chapter; this serves to reinforce the informal narrative style of the text and give students a glimpse into how we teach these topics ourselves.
■ Fifth, because of the positive feedback we received for the first two editions of this text, we added cell biology principles to Chapters 1-4 and revised four of the existing principles to fully embrace this organizational concept for all 14 chapters.

We also added Concept Check questions, with suggested answers, to every major section of each chapter, and we increased the number of multiple-choice questions at the end of every chapter to 10.
In addition to the new elements, we made the following changes in the third edition, by chapter, as follows:

■ Chapter 1. We rewrote nearly all of Chapter 1 to move it away from the traditional role of previewing content in other chapters and towards a more substantive coverage of evolution at the cellular level. Our goal for Chapter 1 is to firmly establish the theme of evolution from the outset so students can view how the molecular differences between cells and organisms arose through the natural selection. This chapter also establishes the themes of teamwork and biological codes, which we feel are critical to understanding the molecular complexity of most cellular functions.
■ Chapter 2. We revised approximately 20% of the content. We added a section describing the variety of RNAs cells produce and imported some of the DNA modification material from Chapter 12 to consolidate the discussion of chromosome remodeling. This provides the background to support our case study on X chromosome silencing. We also corrected some errors in chemical nomenclature.
■ Chapter 3. We made modest updates to the existing text (e.g., a slight expansion of our discussion of protein binding kinetics) and focused most of our revisions on the new elements (callout boxes on ‘omics technologies, home pregnancy test kits, and flu vaccine development).
■ Chapter 4. Per request of many reviewers, we moved sections on membrane transport from Chapter 10 to Chapter 4. We also expanded our discussion of sphingolipids and added visual analogy/exercise—building a membrane “sandwich”—to reinforce the complex composition of biological membranes.

■ Chapter 5. We added a section on membrane anchors and cytoskeletal linkers to expand the classes of actin binding proteins to five.
■ Chapter 6. We added emphasis on the role of extracellular matrix and cell-cell junction proteins to the evolution of multicellular organisms and added a new class of extracellular matrix molecules: matricellular proteins. This new topic provided an opportunity to reinforce the theme that signaling molecules can be embedded in the extracellular space.
■ Chapter 7. Approximately 15% of this chapter has been updated. We revised the principle for this chapter to expand our focus to the role of the nucleus as an organizer and protector of nucleic acids. The principle for the second edition, that DNA integrity is the top priority for cells, is embedded in the new principle. We used this shift in focus to more closely examine how DNA is organized and imported content from Chapter 2 to explain the physical basis of chromosome organization. We also expanded our discussion of DNA replication and the organization of the replication fork.
■ Chapter 8. We updated the principle for this chapter to further emphasize the connections between DNA, RNA, and proteins as forms of cellular information and to illustrate how biological codes are essential to proper collaboration between molecular teams. We also pick up the discussion of RNAs from Chapter 2 and address the multiple ways that cells move different RNA types into and out of the nucleus. The revised chapter also includes an updated description of peroxisomal membrane transport and protein degradation in the endoplasmic reticulum. Finally, we expand the topic of targeted mRNA transport in the cytosol.
■ Chapter 9. The section on the structure and function of the Golgi apparatus was extensively updated to reflect the impact of genomic sequencing on the field. We also added a new section, entitled Peroxisomes Defy Classification, to embrace the growing evidence that the peroxisome is a descendent of both the endomembrane system and mitochondria. This section also provides an opportunity to review the sometimes tortuous path researchers must take to answer such a seemingly simple question as, “where did peroxisomes come from?”

■ Chapter 10. We moved the membrane transport section to Chapter 4 and expanded the discussion of glucose metabolism to include gluconeogenesis and anabolic pathways.
■ Chapter 11. We made minor changes to clarify the content.
■ Chapter 12. We updated approximately 20% of the content, including the sections covering G protein coupled receptor-, phosphatidylinositol-, and protein kinase-mediated signaling in the nucleus; and epigenetic modification of DNA.
■ Chapter 13. We expanded the details of growth factor-mediated signaling and control of the cell cycle, repair of double-stranded DNA breaks, and cytokinesis.
■ Chapter 14. We changed the principle for this chapter to reflect our increased emphasis on cellular evolution and the impact of human activity on all organisms. We retained most of the content on neuromuscular systems and introduced a new section on meiosis and embryonic development. We also added a section on gene editing to capture its central importance on all aspects of biology, from biomedical research to designer organisms.