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T H E C E L L a v i s u a l t o u r o f t h e b u i l d i n g b l o c k o f l i f e JACK CHALLONER consultant editor DR. PHIL DASH T H E C E L L T H E C E L L A V I S U A L T O U R O F T H E B U I L D I N G B L O C K O F L I F E JACK CHALLONER consultant editor DR PHIL DASH THE UNIVERSITY OF CHICAGO PRESS Chicago and London Jack Challoner is the author of more than thirty books on science and technology. He also works as an independent science consultant for print, radio, and TV. The University of Chicago Press, Chicago 60637 The University of Chicago Press, Ltd., London © 2015 by The Ivy Press Limited All rights reserved. Published 2015. Printed in China 24 23 22 21 20 19 18 17 16 15 1 2 3 4 5 Text © Jack Challoner 2015 Design and layout © The Ivy Press Limited 2015 ISBN-13: 978-0-226-22418-3 (cloth) ISBN-13: 978-0-226-22421-3 (e-book) DOI: 10.7208/chicago/978-0226224213.001.0001 Library of Congress Cataloging-in-Publication Data Challoner, Jack, author. The cell : the origin of life / Jack Challoner. pages cm Includes index. ISBN 978-0-226-22418-3 (cloth : alk. paper) — ISBN 978-0-226-22421-3 (ebook) 1. Cells. 2. Cytology. I. Title. QH582.4.C425 2015 571.6—dc23 2015008716 This book was conceived, designed, and produced by Ivy Press 210 High Street, Lewes, East Sussex, BN7 2NS. United Kingdom www.ivypress.co.uk Publisher Susan Kelly Creative Director Michael Whitehead Editorial Director Tom Kitch Art Director James Lawrence Commissioning Editor Jacqui Sayers Project Editor Stephanie Evans Designer Andrew Milne Illustrator Vivien Martineau Picture Researcher Caroline Hensman Color origination by Ivy Press Reprographics ∞ This paper meets the requirements of ANSI/NISO Z39.48-1992 (Permanence of Paper). Front cover image Spike Walker, Wellcome Images. Back cover image Lebendkulturen.de/ Shutterstock, Inc. Contents 6 INTRODUCTION Why the cell is Earth’s greatest success story, and the basis of all life. 10 CHAPTER 1 58 CHAPTER 3 A Brief History Cells Beget Cells of the Cell The process of cell division In the 350 years since cells accounts for growth and were discovered remarkable reproduction, as well as the progress has been made in evolution of new species. our understanding of them. 90 CHAPTER 4 142 CHAPTER 6 28 CHAPTER 2 Cellular Life, Death, and Inside Living Cells Singletons Immortality All types of cell share certain The overwhelming majority Cells have evolved characteristics, including the of cells on Earth are extraordinary ways to attack molecular machinery that individual living things— other cells and to protect makes them work. single-celled organisms. themselves. 118 CHAPTER 5 164 CHAPTER 7 188 GLOSSARY Coming Together— Taking in the INDEX Multicellular Life Cytes ACKNOWLEDGMENTS Cells cooperate within The human body complex organisms manufactures around and perform essential 200 different cell types, specialized tasks. displaying astonishing diversity and specialization. Introduction Every person on this planet began life as one cell, howler monkey, houseplants, a hawk’s beak, a snake’s about the same size as this period. Each one of venom … all of these are the result of activity in cells. us remained like this for about 24 hours before dividing in two—the first step toward creating the What is this life? complex, multicellular organism that humans are The difference between a living and a nonliving thing today. It is an incredible and fascinating thought, has always been difficult to define. Biologists that a human could have been contained in a generally agree that for something to be considered single cell, and that, perhaps more remarkable still, alive it must satisfy a set of criteria, including the use that one basic unit of life knew what to do to next. of energy to build complex molecules and organize its internal systems, and the ability to respond to its To understand just how important cells are, consider surroundings and to reproduce. Rhododendrons and the following. The total number of living things ants satisfy all of these criteria—but only because currently inhabiting our planet is unimaginably they are made of cells, life’s building blocks. Cells large (there are an estimated 8.7 million unique are life, and to understand their behavior, their species, most of them numbering millions, billions, structure and their remarkable microscopic and Left Two become one; light or trillions of individuals), and every last one of submicroscopic machinery is to understand life micrograph (a microscope them, without exception, is made of one or more itself. Chapter one outlines the history of that photograph) of a single, fertilized human egg cell cells. Next, consider the incredible variety of understanding (so far), and examines some of the (ovum) soon before the first processes and materials that occur in the natural tools and techniques that have nurtured it. cell division. world. The glow of a firefly, a plant bending toward Below Anything at all in the the light, cancer, a 100-meter sprint, wood, mucus, A cell is just a mixture of molecules, a cocktail living world, from a material elephant dung, a blue whale’s skeleton, body odor, of chemicals, inside a little bag. Despite the to a process, happens because of activity in cells. the memory of the smell of ratatouille, the call of a unambitious simplicity of that description, INTRODUCTION 7 and the tiny size of a typical cell, truly intricate How big are cells? wonders lie within. This is the subject of chapter Although most individual cells are far too small to see two, the inside view of cells, in which the main without serious magnification, there are some that features are identified and the main types of cell are big enough. Bird eggs, for example, are single are considered. cells. The largest bird egg of a living species is laid by the ostrich, and ostrich eggs are, in fact, the largest The cell is a bewilderingly busy molecular of all cells. (The shell, incidentally, is not part of the metropolis: some molecules are making copies cell but is manufactured by it.) There are millions of of themselves; some are manufacturing other species that remain as single cells all their lives— molecules; some are quickly reading information the ostrich is not among them, of course. Among the coded along the length of others; some are grabbing largest of them is Valonia ventricosa, also known as hold of others and carrying them to wherever they bubble algae, which can grow to 2 inches (5 centimeters) need to be next; some are self-assembling as a kind in diameter. The variety and importance of these of molecular scaffolding or as tracks along which cellular singletons is revealed in chapter four. other molecules can be carried. All of this dizzying activity, and infinitely more, is taking place in The living things with which we are familiar—the every living cell on the planet every moment of ones we can actually see—are made of thousands, every day. Two of the most important outcomes millions, billions, or trillions of cells. Nearly all of this molecular dance—growth and reproduction, multicellular organisms are either plants, fungi, or via the proliferation of cells—form the subject of animals. In most cases the cells that make up these chapter three. organisms all come from repeated cell divisions that HOW STRANGE THE CHANGE FROM MICRO TO MACRO Most cells are too small to be seen with the naked eye, but they are easily observed with light microscopes; they are microscopic. The smallest cells, tiny mycoplasma that live inside other cells, are under one thousandth of a millimeter (1 micron) in diameter, while the largest, such as bird eggs or nerve cells, are inches across. Most types of cell are typically between 5 and 10 microns across. SCALE 2 mm = 1 micron Bacteria cell Red blood cell Human liver cell Plant cell Micrasterias diameter diameter diameter diameter diameter 0.5–5 microns 6–8 microns 10 microns 10 microns 35 microns 8 INTRODUCTION start with one cell—that fertilized egg from which Imagine if all the cells that had ever lived were each of us derived, for example—differentiating into still alive. Nature is a constant battleground in different types that form tissues, which in turn can which cells fight for dominance or sometimes just form sophisticated specialized organs. (In others, a for survival. Competition for space or resources is new individual may begin by budding—by no means a driving force in evolution, a process that simply a lesser feat.) The cells of a multicellular organism would not work without death. Chapter six sets out also produce substances that hold the individual how cells compete and how they die—including together and compounds that enable intercellular the importance of cell self-destruction and the communication. Chapter five looks at how this all problems that failure to self-destruct can cause. works to build a robust, functioning body. Then the final chapter considers the most interesting and vital cells of the human body, all A matter of life and death of which can trace their origins back to the single Strange as it may seem at first, it is of equal cell that heralded the beginning of a new person importance for cells to die as it is for them to live. all those years ago. Human hair cross section diameter 100 microns (x10 cells)