A Signal-Recognition Particle (SRP) Directs ER Signal Sequences to a Specific Receptor in the Rough ER Membrane By Providing an Inexhaustible Source of Reducing Power, Photosynthetic Bacteria Overcame a Major Evolutionary Obstacle Mammalian cells proliferating in culture. The cells in this scanning electron micrograph are rat fibroblasts. (Courtesy of Guenter Albrecht-Buehler.) Transport Between the Nucleus and Cytosol Can Be Regulated by Controlling Access to the Transport Machinery

Bacterial Chemotaxis Depends on a Two-Component Signaling Pathway Activated by Histidine-Kinase-associated Receptors Metal Shadowing Allows Surface Features to Be Examined at High Resolution by Transmission Electron MicroscopyLipid Rafts May Mediate Sorting of Glycosphingolipids and GPI-anchored Proteins to the Apical Plasma Membrane A Strand-directed Mismatch Repair System Removes Replication Errors That Escape from the Replication Machine

Petite Mutants in Yeasts Demonstrate the Overwhelming Importance of the Cell Nucleus for Mitochondrial Biogenesis In Multicellular Animals and Most Plants, the Diploid Phase Is Complex and Long, the Haploid Simple and FleetingMolecular Biology of the Cell, Sixth Edition: The Problems Book by John Wilson and Tim Hunt The Problems Book is designed to help students appreciate the ways in which experiments and simple calculations can lead to an understanding of how cells work. It provides problems to accompany Chapters 1–20 of Molecular Biology of the Cell. Each chapter of problems is divided into sections that correspond to those of the main textbook and review key terms, test for understanding basic concepts, pose research-based problems, and now include MCAT-style questions which help students to prepare for standardized medical school admission tests. Molecular Biology of the Cell, Sixth Edition: The Problems Book should be useful for homework assignments and as a basis for class discussion. It could even provide ideas for exam questions. Solutions for all of the problems are provided in the book. Solutions for the end-of-chapter problems for Chapters 1–24 in the main textbook are also found in The Problems Book Filament Treadmilling and Dynamic Instability Are Consequences of Nucleotide Hydrolysis by Tubulin and Actin Conditional and Induced Somatic Mutations Make it Possible to Analyze Gene Functions Late inDevelopment