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Lippincott Illustrated Reviews: Cell and Molecular Biology Second Edition Nalini Chandar, PhD Professor of Biochemistry Midwestern University Downers Grove, Illinois Susan Viselli, PhD Professor of Biochemistry Midwestern University Downers Grove, Illinois • oc.Wolters Kluwer Philadelphia • Baltimore • New York • London Buenos Aires • Hong Kong· Sydney • Tokyo Acquisitions Editor: Crystal Taylor Product Development Editor: Andrea Vosburgh Marketing Manager: Michael McMahon Production Project Manager: Marian Bell us Editorial Coordinator: Dave Murphy Design Coordinator: Joan Wendt Manufacturing Coordinator: Margie Orzech Prepress Vendor: SPi Global Second Edition Copyright 0 2019 Wolters Kluwer Copyright@2010 Wolters Kluwer Health/Lippincott Williams & Wilkins. All rights reserved. This book is protected by copyright. No part of this book may be reproduced or transmitted in any form or by any means, including as photo copies or scanned-in or other electronic copies, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotations embodied in critical articles and reviews. Materials appearing in this book prepared by individuals as part of their official duties as U.S. government employ ees are not covered by the above-mentioned copyright. To request permission, please contact Wolters Kluwer at Two Commerce Square, 2001 Market Street, Philadelphia, PA 19103, via email at [email protected], or via our website at lww.com (products and services). 9 8 7 6 5 4 3 2 1 Printed in China Library of Congress Cataloging-in-Publication Data I Names: Chandar, Nalini, author. Viselli, Susan, author. Title: Cell and molecular biology I Nalini Chandar, Susan Viselli. Other titles: Lippincott illustrated reviews. I I I Description: Second edition. Philadelphia :Wolters Kluwer, [2019] Series: Lippincott illustrated reviews Includes index. I Identifiers: LCCN 2017054851 ISBN 9781496348500 I I I I I Subjects: MESH: Cells Biological Transport-physiology Cell Physiological Phenomena Genetic Phenomena I Examination Questions Outlines I I Classification: LCC QH581.2 NLM QU 18.2 DDC 611/.0181--dc23 LC record available at https:/llccn.loc. gov/2017054851 This work is provided "as is," and the publisher disclaims any and all warranties, express or implied, including any warranties as to accuracy, comprehensiveness, or currency of the content of this work. This work is no substitute for individual patient assessment based upon healthcare professionals' examination of each patient and consideration of, among other things, age, weight, gender, current or prior medical conditions, medication history, laboratory data and other factors unique to the patient. The publisher does not provide medical advice or guid ance and this work is merely a reference tool. Healthcare professionals, and not the publisher, are solely responsible for the use of this work including all medical judgments and for any resulting diagnosis and treatments. Given continuous, rapid advances in medical science and health information, independent professional verifica tion of medical diagnoses, indications, appropriate pharmaceutical selections and dosages, and treatment options should be made and healthcare professionals should consult a variety of sources. When prescribing medication, healthcare professionals are advised to consult the product information sheet (the manufacturer's package insert) accompanying each drug to verify, among other things, conditions of use, warnings and side effects and identify any changes in dosage schedule or contraindications, particularly if the medication to be administered is new, infre quently used or has a narrow therapeutic range. To the maximum extent permitted under applicable law, no respon sibility is assumed by the publisher for any injury and/or damage to persons or property, as a matter of products liability, negligence law or otherwise, or from any reference to or use by any person of this work. LWW.com Dedication In memory of our parents. This book is dedicated to those we teach and those who taught us. Acknowledgments We are grateful to the team at Wolters Kluwer. We thank Crystal Taylor whose support has been invaluable throughout the course of the first and second editions of this book. We also extend special thanks to Matt Chansky who expertly and patiently transformed our sketches into the works of art that appear as figures throughout this book. We value the support of our colleagues who read and critiqued early versions of the chapters, who served as peer reviewers, and to those who have adopted this title for their courses. We hope that this second edition will be a helpful resource to students of the health professions. In Memoriam Richard A. Harvey, PhD 1936-2017 Cocreator and series editor of the Lippincott Illustrated Reviews series, in collaboration with Pamela C. Champe, PhD (1945-2008). Illustrator and coauthor of the first books in the series: Biochemistry, Pharmacology, and Microbiology and Immunology. Contents UNIT I- Cell and Tissue Structure and Organization Chapter 1: Stem Cells and Their Differentiation ... 2 Chapter 2: Extracellular Matrix and Cell Adhesion ... 11 Chapter 3: Biological Membranes ... 31 Chapter 4: Cytoskeleton ... 40 Chapter 5: Organelles ... 55 UNIT II- Organization of the Euknryotic Genome and Gene Expression Chapter 6: The Eukaryotic Genome ...6 6 Chapter 7: DNA Replication ... 77 Chapter 8: Transcription ... 92 Chapter 9: Translation ... 102 Chapter 10: Regulation of Gene Expression ... 116 Chapter 11: Protein Trafficking ... 127 Chapter 12: Protein Degradation ... 138 UNIT III-Membrane Transport Chapter 13: Basic Concepts of Transport ... 146 Chapter 14: Active Transport ... 155 Chapter 15: Glucose Transport ... 162 Chapter 16: Drug Transport ... 170 UNIT IV-Cell Signaling Chapter 17: G-Protein Signaling ... 176 Chapter 18: Catalytic Receptor Signaling ... 185 Chapter 19: Steroid Receptor Signaling ... 194 UNIT V- Regulation of Cell Growth and Cell Death Chapter 20: The Cell Cycle ... 204 Chapter 21: Regulation of the Cell Cycle ... 212 Chapter 22: Abnormal Cell Growth ... 221 Chapter 23: Cell Death ...2 31 Chapter 24: Aging and Senescence ... 244 lndex. .•2 53 iv UNIT I Cell and Tissue Structure and Organization Unity of plan everywhere lies hidden under the mask of diversity of structure-the complex is everywhere evolved out of the simple. -Thomas Henry Huxley A Lobster; or, the Study of Zoology (1861). In: Collected Essays, Vol. 8. 1894: 205-206. The most basic and simple form of human life is the cell. Complex organisms, such as humans, are collections of these individual cells that have grown and differentiated to generate the organism itself. Each cell in an adult developed in a purposeful way from a precursor cell along a specific lineage to become organized structurally and according to its function. Be it a liver cell, a blood cell, a bone cell, or a muscle cell, it was derived from a stem cell generated soon after the organism's conception. Hidden within the tiny stem cell is the vast capacity to develop into an array of diverse cell types that differentiate into efficient individual units that survive only within the context of the whole person. Our discussion of cell and molecular biology therefore begins with an examination of stem cells, from which all other cells are generated. As we move deeper into this unit, we explore structural components of tissues including the extracellular matrix, which is produced by cells but resides outside the boundary of cell membranes. In considering cell structure, cell membranes serve as our starting point. As the outer limit of the cell, the plasma membrane protects the cell's interior from the environ ment. Yet, it is also a dynamic structure that enables interactions with the environment and facilitates the cell's function. Within the confines of the plasma membrane, we find cytoskeletal proteins that not only organize the cytoplasm and provide a structural framework for the cell but also function in the intracellular movement of chromatin and organelles. The organelles are specialized centers within each cell that carry out func tional processes, including energy extraction in the mitochondria, mac romolecule digestion in the lysosomes, and DNA and RNA synthesis in the nucleus. While each organelle is a complex machine in its own right and has its own unique role within the cell, organelles are linked physi cally by the cytoskeleton and cooperate in completing their tasks with a unified purpose. 1 Stem Cells and Their Differentiation I. OVERVIEW All cells within an organism are derived from precursor cells. Precursor cells divide along specific paths in order to produce cells that are differenti ated to perform specialized tasks within tissue--s and organs. Cells with the capacity to give rise to the whole organism are referred to as stem cells. Stem cells remain undifferentiated ana are c aracterized by the ability to self-renew. They also generate many daaghter cells committed to differen tiate (change) into a diverse range of specialized cell types. A daughter cell with the ability to differentiate info a wide variety of cell types is pluripotent. The human body is made up of al<>out 200 different types of cells. The human genome is the same i all cell types, meaning that within an individual person, all cells Have exactly the same DNA sequences and genes. Stem cells represent all the different ways that human genes can be expressed as proteins. In order for different regions of the genome to be expressed in crtterent cell types, the genome has to be reversibly modified. In fact, the organization of chromatin (a complex of specific proteins an QNA) varies between cell types and is made possible by reversible covalent modification of the proteins that are associated with DNA and sometimes the DNA itself (see also Chapter 6). These modifi eations are important to expose regions of the DNA to the proteins and e~ymes that are required for transcription (DNA ➔ RNA), allowing for variation in gene expression as proteins (see also Chapter 8). Different cell types arise from precursor cells that proliferate (divide) and eventually differentiate into cells with unique structures, functions, and chemical composition. From specific proteins produced in the cells, a special type of cell division, and the microenvironment of the precursor cell, a progeny of cells is produced. This progeny can both sustain the organism and carry out specific functions in the body. II. STEM CELLS Stem cells exist in both early embryos and adult tissues (Figure 1.1 ). The stem cells present in early embryos have an extensive capacity to differ entiate into all cell types of the organism. Populations of stem cells also exist in adults and can differentiate into various cells within a lineage but not outside that lineage. For example, a hematopoietic stem cell (HSC) can differentiate into various types of blood cells but not into a hepatocyte (liver cell). However, researchers may have found new properties of adult 2 II. Stem Cells 3 .Tot ipotent a-cell stage ..... ..... .. Egg 4-cell stage, totipotent cells ,________~, '~ ~ ~ ~ ~ Epidermis Neurons Pigment Cardiac Skeletal Kidney Red Bone Pancreatic Thyroid Liver Sperm Egg cells muscle muscle tubule blood cells- cell cells cells cells cells cells osteoblasts '-----------------i[ Unipotent Jr----------------------' Figure 1.1 Embryonic and adult stem cells. stem cells, which under certain conditions allow differentiation into more cell types than previously recognized. • Totipotency is the potential of a single cell to develop into a total organism (e.g., a fertilized egg and the four-cell stage). • Pluripotency is a cell's capacity to give rise to all cell types in the body but not to the supporting structures, such as the placenta, amnion, and chorion, all of which are needed for the development of an organism. • Multi potency is a cell's capacity to give rise to a small num ber of different cell types. • Unipotency is a cell's capacity to give rise to only one cell type. A. Pluripotent stem cells The most primitive, undifferentiated cells in an embryo are embry onic stem cells (ESCs). These cells are derived from the inner cell mass of preimplantation embryos (Figure 1.1) and can be maintained in the pluripotent state in vitro. They can give rise to all the three germ layers (ectoderm, mesoderm, and endoderm) with the ability to dif ferentiate into a number of cell types. This ability to differentiate into multiple cell types is called plasticity (Figure 1.2). 4 1. Stem Cells and Their Differentiation B. Unipotent stem cells Cells that reside within adult tissues and retain the ability to generate cells for the tissue type to which they belong are unipotent. Under normal situations, unipotent stem cells give rise to only one cell type. For example, a myoblast (muscle cell precursor) can give rise to a myocyte (muscle cell), and a hepatoblast (liver cell precursor) can give rise to a hepatocyte (liver cell). C. Multipotent stem cells Adult multipotent stem cells have been identified for a number of dif ferent tissue types such as brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin, and liver (Figure 1.2). 1. Hematopoietic stem cells: This group of stem cells gives rise to all the types of blood cells, including red blood cells, B lympho cytes, T lymphocytes, natural killer cells, neutrophils, basophils, eosinophils, monocytes, macrophages, and platelets. Figure 1.2 2. Mesenchymal stem cells: Also called bone marrow stromal Adult stem cell plasticity. cells, mesenchymal cells give rise to a variety of cell types, includ ing osteoblasts (bone cells), chondrocytes (cartilage cells), adipo cytes (fat cells), and other kinds of connective tissue. 3. Skin stem cells: These stem cells are found in the basal layer of the epidermis and also at the base of hair follicles. Epidermal stem cells give rise to keratinocytes, while the follicular stem cells give rise to both hair follicles and the epidermis. 4. Neural stem cells: Stem cells in the brain can differentiate into its three major cell types: nerve cells (neurons) and two types of non neuronal cells-astrocytes and oligodendrocytes. 5. Epithelial stem cells: Located in the lining of the digestive tract, epithelial stem cells are found in deep crypts and give rise to sev eral cell types, including absorptive cells, goblet cells, Paneth cells, and enteroendocrine cells. Ill. STEM CELL COMMITMENT Most stem cells first become intermediate progenitor cells (also known as transit amplifying cells), which then produce a differentiated population of cells. A good example of this stepwise process is illustrated by HSCs. HSCs are multipotent but undergo commitment into a particular pathway in a step wise process. In the first step, they give rise to two different progenitors. The committed progenitors then undergo many rounds of cell division to produce a population of cells of a given specialized type. In this particular case, the HSCs give rise to one type that is capable of generating lymphoid cells and another type that results in the generation of myeloid cells (Figure 1.3). The different steps of commitment happen due to changes in gene expression. Genes for a particular pathway are switched on, while access to other developmental pathways is shut off by specific proteins that bind DNA and act as transcription factors (see Chapter 10 ). These proteins are able to both activate the genes necessary for a particular pathway and shut down the expression of genes necessary for development along a different pathway.

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