Life’s Energy

Stefan Bröer

Description

What energises humans to move and think? Whether we wake up groggy and say that we have no energy to do anything or whether we wake up refreshed and feel ready to tackle the day, scientists and non-scientists alike acknowledge that energy is essential for anything to happen. However, not everyone knows and digs deeper into what energy actually is. In the human body, energy can be followed by looking at one molecule. In “Life’s Energy” the reader is guided through our bodies molecular world to understand of how a single molecule, Adenosine Triphosphate (ATP), can drive life. The book goes back in history to see how ATP was discovered. Then it follows ATP around the body and explains what it does, how it is maintained and explores its role in diseases such as diabetes and cancer. Along the way it introduces the scientists involved in ATP research, how their research activity was affected by the rise of the “Third Reich” and why many of them were awarded Nobel Prizes for their insights.

Sujets

• Sciences et techniques
• Energy
• Science

Informations

• Publié par: Xlibris AU
• Date de parution: 20 novembre 2022
• Nombre de lectures: 0
• EAN13: 9781669832591
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

LIFE’S ENERGY
 
 
 
 
STEFAN BRÖER
 
 
Copyright © 2022 by Stefan Bröer.
 

Library of Congress Control Number:
2022920175
ISBN:
Hardcover
978-1-6698-3261-4

Softcover
978-1-6698-3260-7

eBook
978-1-6698-3259-1
 
 
All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the copyright owner.
 
Any people depicted in stock imagery provided by Getty Images are models, and such images are being used for illustrative purposes only.
Certain stock imagery © Getty Images.
 
 
 
 
Rev. date: 11/07/2022
 
 
 
Xlibris
AU TFN: 1 800 844 927 (Toll Free inside Australia)
AU Local: [phone] ([phone] from outside Australia)
www.Xlibris.com.au
 
844150
CONTENTS
1     The Energy of Life
2     A Missed Nobel Prize
3     Around the Arc de Triomphe
4     The Bar-Headed Goose
5     ATP Meets Frankenstein
6     Hibernating Bears
7     Mythbusters and Blockbusters
8     Hermes Delivers the Message
9     Marjorie Paws the Way
10   The Hydrophobic Vacuum Cleaner
11   The Demon Under the Microscope
12   Epilogue
References
1
The Energy of Life
While there is life there is hope. I beg to assert . . . that as long as a man’s heart beats, as long as a man’s flesh quivers, I do not allow that a being gifted with thought and will, can allow himself to despair.
-Jules Verne, Journey to the Center of the Earth
When we use the word ‘energy’, we use it in two different contexts. One is our psychological state; the other is energy as work and exercise. We often say, ‘I feel energetic today’ or we feel ‘deflated and lack motivation’. This has relatively little to do with how our body generates energy to carry out work, or to energise our brain. Our body is always ready to generate more energy even if we feel deflated. Most of this book deals with not only the energy to carry out work and exercise but also the energy required to think, generate emotions, and let our organs work. For all of this, our body uses but one molecule. Despite its importance, it is not known in the wider population, but this book will put it centre stage.
This molecule is called ATP or by its proper name a denosine t ri p hosphate (or adenosine with three phosphates, simplified in Figure 1), which is to any biochemist the energy of life. Do not worry about the chemistry; this book will explain all concepts at a level suitable for any science-interested reader. I will not show chemical formulas throughout the book, but for ATP, I must make an exception because there is no other way to introduce it properly.
Adenosine is made up of a molecule called adenine linked to a sugar. We don’t need its precise structure, but the adenine-sugar part serves as a key, so ATP can only enter places where the key fits. The business end of the molecule is the three phosphate groups, which provide the energy. When furnished with phosphates, it is called a nucleotide. In Figure 1, the phosphates are shown as a P in a circle. In case you asked, phosphate is a phosphorous atom bonded to four oxygen atoms. Phosphate is very stable and easily soluble in water.

Figure 1. Simplified depiction of ATP. Phosphate is shown as a circle with a P . Adenosine is made up of sugar plus adenine. Splitting of a phosphate with water releases energy.
As an example, Coca-Cola contains about 0.2 g of phosphate per litre. The oxygen atoms can build a link between phosphate molecules, and this is how the three P s are connected in ATP. Water can be used to break this bond, and when this happens, energy is released. It is quite easy to break this bond; if the water is made acidic, it will happen spontaneously. This is important because it shows that the energy in this bond is readily released. Or in other words, the products are more stable than the ATP. When this happens, the shortened molecule is called ADP, which stands for adenosine diphosphate.
Most people know ATP as the Association of Tennis Players, which is a segue to my first example to illustrate the role of ATP. A tennis player uses about 23 kg of ATP per hour in a tennis match. This is quite astounding because the tennis player is not losing 23 kg body weight, but she is using all the energy provided by the release of 4.4 kg phosphate groups. In fact, she is only going to lose 60 g of body weight per hour, in the form of carbohydrates and fat. After the match, the balance will say that she lost more weight, but this is only water as sweat. This also explains why it is so disappointing to lose weight just with exercise. The difference between using 23 kg ATP and losing 60 g of stored nutrients suggests that ATP is constantly split into ADP and phosphate and quickly fused together again to reform ATP during the tennis game. Something is churning in her body, maintaining high energy levels for a match that can last three hours. How is this possible? We will explore the reactions that recycle ADP back to ATP in the next chapters.
Actually, our body is not that expensive to run. We only use as much as a 100 W light bulb when resting, but I think we are getting more value for money out of our body than from a 100 W light bulb. A professional cyclist, however, can produce another 300–400 W when cycling uphill or more than 1,000 W during brief bursts of activity.
An effective way to understand the role of ATP is by comparing it to money. I will use the economy as an analogy several times in this book because our body is a good bookkeeper of energy expenditure and intake. You can view ATP as cash. To stay close to the analogy, you can buy electricity or petrol with cash. This will provide you with energy that you can use for a lot of things, such as heating your house (keeping your body temperature), driving around (exercising your body), or running a computer (running your brain). One molecule of ATP is a small amount of cash, like a one-dollar coin (or one euro or whatever you prefer). In the economy, currencies go up and down in value, and so does ATP. Our body is desperate to keep it at one dollar, but during strenuous exercises, its value may go down to ninety or eighty cents in muscle. This initiates a lot of emergency responses to bring it back to one dollar. If we have a stash of ATP and ADP, we want ten molecules of ATP for each molecule of ADP. In that case, our ATP is worth one dollar. If this goes down to let us say eight molecules of ATP and three molecules of ADP, our body energy is running low already. Muscle is reasonably tolerant to devaluation; we just get fatigued and stop running, but not our brains or our hearts. A heart attack is so dangerous because our ATP is devalued very suddenly, and then the heart stops beating. If that happens in the brain, it is called a stroke, and our neurons stop working and die. We will come back to this later in much more detail, but it nicely illustrates the importance of ATP. As in real life, if we spend money, we need to refill our purse by having a job that provides us with a salary. In the case of ATP, that is called nutrition and is used to convert ADP back to ATP. In short, we need to eat to keep ATP up at one dollar. To be realistic, ATP is much smaller than a dollar. We may spend a couple of hundred dollars in a day, but 23 kg of ATP represents 2.7 x 10 25 molecules. To give you an idea of the scale, one molecule of ATP compared to the total of 23 kg is like a shot of whiskey compared to the total volume of all oceans on earth. ATP is a very small coin indeed, and we are going through a lot of it because exercise requires a lot of energy.
What kind of energy is released when ATP splits into ADP and phosphate? It is vibrational energy. 1 Whatever the ATP is attached to will wobble and shake. Wobble and shake at the level of a molecule is the same as heating. When water boils, it is rolling because the water molecules bounce and wobble so much that they become a gas instead of a liquid. Splitting ATP is like a local heater bringing the molecule to 3900 °C. 1 This is the reason why ATP is such a small but powerful unit of energy. At a larger scale, everything would just be scorched, because the water would evaporate, and everything clumps together into an unrecognisable mess. Remarkably, humans turn over more energy per second than the equivalent weight of sun material. 2 When the heat of splitting ATP is applied locally, however, the wobbling will provide force to do something. It is also important that the wobbling is not transferred to water molecules in the surrounding because this would only heat up the water. To some extent, this is unavoidable and the reason we warm up when we exercise, but a good chunk of the energy is used to do work. To form ATP, the opposite must happen. We have to apply energy very locally to fuse ADP and phosphate together to make ATP.
As we will see throughout the book, the vibrational energy associated with the splitting of phosphate from ATP can be used for many things, such as contracting muscles, pumping ions, facilitating chemical reactions, and switching proteins on or off.
The relation between work, heat, and energy was established during the Industrial Revolution. 3 Particularly important was the observation that different forms of energy can be