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- Herausgeber: David Fickling Books
- Kategorie: Für Kinder und Jugendliche
- Serie: Explodapedia
- Sprache: Englisch
Highly commended at the Association for Science Education Book of the Year Awards 2023!Cells are alive, and they're what life is made of. Four billion years ago a single cell kickstarted all life on Earth. Today, your body is made up of over 30 trillion cells - every one of which is teeming with activity.Packed with up-to-the-minute science, The Cell confronts the biggest mysteries of the microscopic marvels that sustain the living world. Can cells save our planet next?Explode your knowledge about cells, with the EXPLODAPEDIA!
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Welcome to Explodapedia, the indispensable guide to everything you need to know! This series is packed with in-depth knowledge you can trust; it gives you the tools you need to understand the science behind the wonders of our world. Our story begins withThe Cell, the secret at the heart of all life.
‘I had no idea cells were so interesting (or funny)!’Greg Jenner
‘Easy to read for anyone curious about what science has and is discovering… Prepare to be amazed!’Sir Paul Nurse, Nobel Prize winner
‘The perfect balance between charm, quirkiness and wonder… for kids and adults alike.’Siddhartha Mukherjee, Pulitzer Prize winner
‘[These books] lead their readers willingly to the wonders of the biological world.’Professor Richard Fortey
‘Both accessible and funny… a clever way to introduce… our understanding of all life today.’Professor Venki Ramakrishnan, Nobel Prize winner1
BM: To Fi, who gave me the first cell I ever had.
AA: To Karen, Connor and Spencer, my favourite conglomerations of cells on the planet.
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EXPLODAPEDIA: THE CELL First published in 2023 by David Fickling Books, 31 Beaumont Street, Oxford, OX1 2NP
This ebook edition first published in 2023
All rights reserved Text © BEN MARTYNOGA, 2023 Illustrations © MOOSE ALLAIN, 2023
The right of Ben Martynoga and Moose Allain to be identified as the author and illustrator of this work has been asserted in accordance with Section 77 of the Copyright, Designs and Patents Act 1988.
This ebook is copyright material and must not be copied, reproduced, transferred, distributed, leased, licensed or publicly performed or used in any way except as specifically permitted in writing by the publishers, as allowed under the terms and conditions under which it was purchased or as strictly permitted by applicable copyright law. Any unauthorised distribution or use of this text may be a direct infringement of the author’s and publisher’s rights, and those responsible may be liable in law accordingly.
ISBN 978–1–78845–248–9
Italic type is used in Explodapedia to highlight words that are defined in the glossary when they first appear, to show quoted material and the names of published works. Bold type is used for emphasis.4
Contents
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The Cell
Our story starts a very, very long time ago, in a hot, dark and mysterious place deep under the sea. The hero is a single cell. Now, this cell couldn’t really have had a name and wasn’t male or female, but let’s call it Luca.
Planet Earth was young and grumpy. Meteorites pummelled its surface and volcanoes were everywhere, venting lava and belching poisonous gases. The air contained no oxygen, and since there was no proper atmosphere to absorb it, ultraviolet radiation from the sun frazzled the planet. It was not a pleasant place to be.7
Luca wasn’t much more than a tiny bubble of living matter – a thin membrane skin on the outside and a mixture of chemicals on the inside. And Luca couldn’t do any of the fancy things that many of the cells that make up your body can do, like sense light, sprout hairs or carry nerve impulses. Nevertheless, this tiny cell was hellbent on dominating the universe.
But do you know what? Luca’s world-conquering plan was working. That’s because, four billion years ago, Luca managed to self-reproduce. Self-reproduction basically means making a copy of yourself, and here’s how it happened.
First the little cell grew a bit, and then it divided into two. Simple.
Now Luca had a twin.
Each twin divided again.
Then there were four cells.
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Those cells doubled again to make eight. And again (16). And again (32), and again, and again.
After this had happened 10 times, over 1,000 Lucas had been born.
After just 60 of these divisions, things were getting a bit out of hand: as many as 1,152,921,504,606,847,000* Lucas had entered the world.
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Luca was special because it was the first cell that truly mastered the ability to reproduce by dividing one cell into two. And, thinking about it, for one cell to build another new and more or less identical cell completely from scratch is pretty amazing. But that’s self-reproduction for you. And if it sounds like quite a straightforward thing to do, it most definitely isn’t.
This kind of self-reproduction was the little cell’s superpower.
Luca was lucky enough to carry a sort of personal instruction manual around on its insides, written in a chemical language called DNA (more on this later). The DNA contained detailed plans for building the cell, keeping it alive, dividing it in two and, crucially, making sure that each new cell carried exactly the same plans for making more Lucas. Without DNA, cells would never have been able to reproduce themselves.
It was lucky, too, that Luca had found the perfect spot to hang out: a hydrothermal vent – that’s a crack in the seabed where hot mineral-rich water and gas pour out of the Earth’s crust and mingle with the seawater. Luca sucked up a never-
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ending stream of hot chemicals from the vent and used them to make all the energy a little cell could possibly need to keep on growing and dividing.
With a reliable source of energy and the ability to self-reproduce, a world of opportunities opened up for Luca.
Next stop, global domination …
Your Least Famous but Most Important Ancestor
Well, what if you found out that Luca is part of your family? Your direct ancestor, in fact. Which basically means: no Luca, no you.
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And look out of the window. See all those living things? They might look different, but they actually all have a huge amount in common.
They’re all either cells or made from cells. In fact, all living things on this planet are based on cells. No cells, no life.
Most cells are so tiny that they’re completely invisible without a powerful microscope. But we know they’re there.
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What you think of as ‘you’ is made from several trillion human cells. A cat – because it is smaller than you – is made from rather fewer cat cells, all working together to make a cat. And that great big apple tree is made from rather more apple tree cells. That festering apple, meanwhile, is a riot of cellular activity:
And, believe it or not, every single one of those cells is Luca’s direct descendant. You see, Luca wasn’t the very first cell, or even the very first living thing on the planet. But it was the first cell that divided and whose offspring survived and thrived.
What that means is that every single creature alive today is related to Luca*, so they are all related to each other. And to you. No Luca, no life.
*Luca’s name actually stands for Last Universal Common Ancestor.
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A Planet of Cells
All those cells that Luca started producing four billion years ago have just kept on dividing and multiplying ever since. For year after year, millennium after millennium, they’ve gone on producing more and more cells.
Today, cells live on and in every nook and cranny of our planet’s surface:
Scientists have even discovered cells floating in the air several kilometres up in the atmosphere, as well as more than
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a kilometre below ground inside hot, dark crushing rocks. And, as far as we know, they’re all living very contented lives.
In short, cells are everywhere, and they’re all related. Every single cell that’s alive today is connected to the same gigantic family tree. And Luca is the tiny seed that this entire family has grown from.
The little family of cells that Luca started to raise four billion years ago has coped with any number of volcanic eruptions, earthquakes, tsunamis and meteorite strikes. Not to mention the constant attacks of deadly viruses, famines and all manner of other battles for survival. Along the way, such a vast number of Luca’s family members have died that scientists couldn’t even begin to count them. And billions more cells die every second. But somehow, against all the odds, Luca’s family clung on and flourished. Luca’s family is your family. It’s our family. We call this family ‘life’, and we are all in it together.
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CHAPTER 1
What is a Cell?
Survival Machines
Dump a rock in your garden, and it will sit there for years, doing very little indeed. Build a snowman, and before too long it will melt into a muddy puddle (unless you live near the South Pole!).
That’s just the way things go for most of the stuff in our world. Things tend to either stay pretty much the same, or they get broken, decay or fall to pieces. Which is why, despite the best of intentions, your bedroom always gets messier with time.
Living things are different. They are full of activity, always changing and constantly working hard to maintain themselves. And living things grow. They multiply. In fact, life seems hellbent on surviving and creating more life.
Plant an apple pip in your garden and, all being well, the little
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seed will sprout in the spring. Eventually, that brave green shoot turns into a young tree. The sapling grows. More branches appear, more leaves, a thicker trunk and ever deeper roots.
And it’s not only the tree that flourishes. Over time, lichens and mosses spread across its bark. Worms, beetles, woodlice and other little critters take up residence beneath the soil, and slender strands of fungus wrap tightly round the tree’s roots. Bacteria and viruses drift in on the breeze and try their luck at infecting the tree. A blackbird decides that the highest branch makes a convenient singing perch. The cat decides this is a rich hunting ground.
Eventually, the new tree bears fruit. And in the core of each shiny red apple are five or six little pips, each of which carries the potential to grow into an entire new tree. The whole process can start again.
Life is brilliant at making more life.
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True, but we mustn’t ever take it for granted. The life forms here on Earth are truly, utterly unique.
Think about it: the universe is unbelievably massive, but this is the only
part of it where we know for certain that life exists. That means there could be more life blooming under the nail of your little finger than there is in the rest of the cosmos.
All objects are made from the same stuff – chemical atoms and molecules – and they all obey the same physical laws, like gravity. So why are living things so completely different from the boring rock, the melting snowman and your untidy bedroom?
An important clue to unravelling that mystery is the fact that life is made from cells.
This is actually the single most important thing to know about cells – and the key to understanding what they are. The cell is the basic unit of life. It’s the smallest thing that has all the features necessary for it to be considered alive. Everything that is alive is either a cell or a collection of cells.
A cell is like a miniature machine, built entirely from
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chemicals and fuelled by chemicals. Each of these cell machines aims to build itself up, maintain itself and keep itself running for as long as it possibly can. To do that it has to start up a huge number of different chemical reactions and then do all it can to keep them going, come what may.
Think of a juggler in a circus – if she drops her flaming clubs, the crowd boos and her act is basically over. If a cell fails to keep its chemical reactions going, it’s not just the show that ends, the cell itself dies.
Because of this need to keep going, each and every cell is a restless, fizzing little bubble of life, whose only ambition is to survive and reproduce. All cells that are alive today inherited this ambition from Luca, their most ancient ancestor.
When you consider the fact that many – perhaps even most – cells spend their entire existence as single cells, the idea that they are all independent living things might seem kind of obvious.
That’s how most bacteria live. There are billions of different kinds of them, and they turn up absolutely everywhere (at this very moment there are trillions of them living inside your guts, up your nose, under your armpits and pretty much everywhere
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else on and in your body). And bacteria cells are most definitely alive.
Think of all the cells that make up the bodies of plants and animals. They’re all living individuals too. If you cut some of those cells off from the main body that grew them, they don’t just curl up and die. Not immediately, at least.
When you bite into an apple, you’re actually chomping up millions of still living apple cells!
Cells of all fresh fruit and veg are 100% alive, until they droop and rot.
