Comparative Anatomy is Largely the Story of the Struggle to Increase Surface in Proportion to Volume

On Being the Right Size,
by J. B. S. Haldane.

J. B. S. Haldane’s essay “On Being the Right Size” is a classic. In the first chapter of Intermediate Physics for Medicine and Biology, Russ Hobbie and I quote it.

You can drop a mouse down a thousand-yard mine shaft; and arriving at the bottom, it gets a slight shock and walks away. A rat is killed, a man is broken, a horse splashes.

Another line from the essay is nearly as famous.

Comparative anatomy is largely the story of the struggle to increase surface in proportion to volume.

We describe the interplay between surface and volume in Chapter 2 of IPMB

Consider the relation of daily food consumption to body mass. This will introduce us to simple scaling arguments. As a first model, we might suppose that each kilogram of tissue has the same metabolic requirement, so that food consumption should be proportional to body mass [or volume]. However, there is a problem with this argument. Most of the food that we consume is converted to heat. The various mechanisms to lose heat—radiation, convection, and perspiration—are all roughly proportional to the surface area of the body rather than its mass.

If ridding our bodies of excess heat is an important issue, then we need to increase surface area without increasing volume. A similar issue arises when getting oxygen to our cells. Our circulatory and respiratory systems are elaborate strategies to increase the area over which oxygen diffuses. This is a key concept where physics and physiology overlap.

You can read Haldane's essay in its entirety here. Below I quote part of it. Enjoy!

Animals of all kinds find difficulties in size for the following reason. A typical small animal, say a microscopic worm or rotifer, has a smooth skin through which all the oxygen it requires can soak in, a straight gut with sufficient surface to absorb its food, and a single kidney. Increase its dimensions tenfold in every direction, and its weight is increased a thousand times, so that if it is to use its muscles as efficiently as its miniature counterpart, it will need a thousand times as much food and oxygen per day and will excrete a thousand times as much of waste products.

Now if its shape is unaltered its surface will be increased only a hundredfold, and ten times as much oxygen must enter per minute through each square millimetre of skin, ten times as much food through each square millimetre of intestine. When a limit is reached to their absorptive powers their surface has to be increased by some special device. For example, a part of the skin may be drawn out into tufts to make gills or pushed in to make lungs, thus increasing the oxygen-absorbing surface in proportion to the animal’s bulk. A man, for example, has a hundred square yards of lung. Similarly, the gut, instead of being smooth and straight, becomes coiled and develops a velvety surface, and other organs increase in complication. The higher animals are not larger than the lower because they are more complicated. They are more complicated because they are larger. Just the same is true of plants. The simplest plants, such as the green algae growing in stagnant water or on the bark of trees, are mere round cells. The higher plants increase their surface by putting out leaves and roots. Comparative anatomy is largely the story of the struggle to increase surface in proportion to volume. Some of the methods of increasing the surface are useful up to a point, but not capable of a very wide adaptation. For example, while vertebrates carry the oxygen from the gills or lungs all over the body in the blood, insects take air directly to every part of their body by tiny blind tubes called tracheae which open to the surface at many different points. Now, although by their breathing movements they can renew the air in the outer part of the tracheal system, the oxygen has to penetrate the finer branches by means of diffusion. Gases can diffuse easily through very small distances, not many times larger than the average length traveled by a gas molecule between collisions with other molecules. But when such vast journeys—from the point of view of a molecule—as a quarter of an inch have to be made, the process becomes slow. So the portions of an insect’s body more than a quarter of an inch from the air would always be short of oxygen. In consequence hardly any insects are much more than half an inch thick. Land crabs are built on the same general plan as insects, but are much clumsier. Yet like ourselves they carry oxygen around in their blood, and are therefore able to grow far larger than any insects. If the insects had hit on a plan for driving air through their tissues instead of letting it soak in, they might well have become as large as lobsters, though other considerations would have prevented them from becoming as large as man.

One Hundred Books About Physics for Medicine and Biology

When I was in high school, I became intrigued by St. John’s College and their Great Books program. I had their brochure, which included a list of the books to read each year; the most famous works of western civilization.

In the spirit of St. John’s, below I list one hundred Great Books about physics applied to medicine and biology. Read all these and you will have obtained a liberal education in biological and medical physics. One book you won’t find on this list is Intermediate Physics for Medicine and Biology. I’m going to assume you’ve already read IPMB and my goal is to suggest books to supplement it.

Where to begin? I’ll assume you have taken a year of physics and a year of calculus. Once you have these prerequisites, start reading.

1. Powers of Ten. First an overview that’s easy and fun. It provides an intuitive feel for the relative sizes of things. 
2. The Machinery of Life. Although I’m assuming you’ve studied some physics and math, I’m not assuming you have much background in biology. This book provides a gentle introduction to biochemistry. Plus, it has those wonderful drawings by David Goodsell. 
3. The Art of Insight in Science and Engineering. Remember: We seek insight, not just facts.
4. Physical Models of Living Systems. IPMB is about modeling in medicine and biology. Philip Nelson’s little book gets us started building models. 
5. The Feynman Lectures on Physics. I know, I know...you’ve already studied introductory physics, but The Feynman Lectures are special. You don’t want to miss them, and they contain some biology too.
6. Air and Water. Now we get to our main topic: physics applied to biology. Mark Denny’s book covers many topics found in the first half of IPMB.
7. Physics with Illustrative Examples from Medicine and Biology. This classic three-volume set covers much of the same ground as IPMB.
8. The Double Helix. To further strengthen your background in biology, read James Watson’s first-person account of how he and Francis Crick discovered the structure of DNA. It’s a required text for any student of science, and is an easy read.
9. The Eighth Day of Creation: The Makers of the Revolution in Biology. After warming up with The Double Helix, it’s time to dig deeper into the history and ideas of modern biology. Physicists play a large role in this book, and it’s wonderfully written.
10. Biomechanics of Human Motion. Chapter 1 in IPMB covers statics applied to the bones and muscles of the body. It’s our first book that focuses in detail on a specific topic.
11. Structures, or Why Things Don’t Fall Down. A delightful book about mechanics, including some biomechanical examples. It’s one of the most enjoyable books on this list. Don’t miss the sequel, The New Science of Strong Materials.
12. Biomechanics: Mechanical Properties of Living Tissue. We need a book about biomechanics that treats tissue as a continuous medium. YC Fung’s textbook fills that niche.
13. A Treatise on the Mathematical Theory of Elasticity. This book is long and technical, and may contain more material than you really need to know. Nevertheless, it’s a great place to learn elasticity. I’m sure there are more modern books that you may prefer. Skip if you’re in a hurry.
14. The Physics of Scuba Diving. An easy read about how hydrostatics impacts divers.
15. Life in Moving Fluids. Fluid dynamics is one of those topics that’s critical to life, but is often skipped in introductory physics classes. This book by Steven Vogel provides an excellent introduction to the field of biological fluid dynamics.
16. Vital Circuits. Another book by Vogel, which focuses on the fluid dynamics of the circulatory system. 
17. Boundary Layer Theory. This large tome may be too advanced for the list, but I learned a lot from it. Skip if you need to move along quickly.
18. Textbook of Medical Physiology. We need to get serious about learning physiology. This classic text is by Arthur Guyton, but any good physiology textbook will do. Not much physics here. The book contains more biology than we need, but physiology is too important to skip.
19. e, The Story of a Number. A gentle introduction into calculus and differential equations, and a great history of the exponential function, the topic of IPMB’s second chapter.
20. Quick Calculus. Yes, you already studied calculus. But we are about to get more mathematical, and this book will help you brush up on math you may have forgotten. If you don’t need it, move on. 
21. Used Math. Finish your math review with this outline of mathematics essential for college physics.
22. The Essential Exponential. It’s time to focus specifically on the exponential function and its properties, so important in biology and medicine.
23. A Change of Heart. Chapter 2 of IPMB mentions the Framingham heart study. Read the story behind the project.
24. On Being the Right Size. This is really an essay, but indulge me while I include it here among the books. J. B. S. Haldane is too fascinating of a writer to miss.
25. Scaling: Why is Animal Size so Important? Knut Schmidt-Nielsen’s study of scaling, a key topic in Chapter 2 of IPMB.
26. Lady Luck. Chapter 3 of IPMB requires us to know some probability, and Warren Weaver’s book is an engaging introduction.
27. Statistical Physics. The first few sections of Chapter 3 in IPMB develop the ideas of statistical physics in a way reminiscent of Frederick Reif’s volume in the Berkeley Physics Course.
28. An Introduction to Thermal Physics. For those who want a more traditional approach to thermodynamics, I recommend Daniel Schroeder’s textbook.
29. Lehninger Principles of Biochemistry. Biological thermodynamics overlaps with biochemistry. Any good biochemistry book will do. They all contain more detail than you need, but a biological physicist must know some biochemistry.
30. The Second Law. This delightful book by Peter Atkins will fill a hole in IPMB: a penetrating discussion about the second law of thermodynamics.
31. Div Grad Curl and All That. Chapter 4 of IPMB uses vector calculus, and there is no better introduction to the topic.
32. Random Walks in Biology. Howard Berg’s wonderful little book about diffusion.
33. The Mathematics of Diffusion. John Crank’s intimidating giant tome about diffusion. Mathephobes shouldn’t bother with it; Mathephiles shouldn’t miss it.
34. Conduction of Heat in Solids. Like the book by Crank, this ponderous textbook by Horatio Carslaw and John Jaeger presents all you ever want to know about solving the heat equation (also known as the diffusion equation).
35. How Animals Work. Another delightful book by Schmidt-Nielsen that considers comparative physiology, and topics in Chapter 5 of IPMB such as countercurrent heat exchange.
36. The Nuts and Bolts of Life. A colorful book about the first dialysis machine.
37. The Biomedical Engineering Handbook. Don’t read this encyclopedia-like multi-volume handbook in one sitting. Yet it provides dozens of examples of how physics is applied to medicine. Ask your library to buy this set and the next one.
38. Encyclopedia of Medical Devices and Instrumentation. The title should be Case Studies: How Physics is Applied to Medicine.
39. Plant Physics. IPMB doesn’t say much about plants, but physics impacts botany as well as zoology.
40. Nerve, Muscle, and Synapse. Bernard Katz’s excellent, if somewhat dated, introduction to all the electrophysiology you need for Chapter 6 of IPMB.
41. The Conduction of the Nervous Impulse. Read about the Hodgkin-Huxley model from the pen of Alan Hodgkin himself.
42. From Neuron to Brain. A modern introduction to neuroscience.
43. Electricity and Magnetism. This book by Ed Purcell is part of the Berkeley Physics Course. The first of three physics books about electricity and magnetism.
44. Introduction to Electrodyamics. David Griffiths’s text competes with Purcell’s for my favorite electricity and magnetism book.
45. Classical Electrodynamics. John David Jackson’s famous graduate-level physics text may be more electricity and magnetism than you want, but how could I leave it off the list?
46. Galvani’s Spark. A history of neurophysiology.
47. Shattered Nerves. A fascinating look at using electrical stimulation to compensate for neural injury. A history of neural prostheses.
48. Bioelectricity: A Quantitative Approach. The first, and probably easiest, of three bioelectricity textbooks.
49. Bioelectromagnetism. Jaakko Malmivuo and Robert Plonsey’s big book about bioelectricity.
50. Bioelectricity and Biomagnetism. Another big tome. Ramesh Gulrajani’s alternative to Malmivuo and Plonsey.
51. The Art of Electronics. In order to understand voltage clamping and other electrophysiological methods, you need to know some electronics. This book is my favorite introduction to the topic. 
52. Mathematical Handbook of Formulas and Tables. Chapter 6 contains lots of mathematics, and the next three books are references you may want. This Schaum’s Outline contains most of the math you’ll ever need. It’s cheap, light, and easy to use. Keep it handy.
53. Handbook of Mathematical Functions with Formulas, Graphs and Mathematical Tables. No one would sit down and read this handbook straight through, but “Abramowitz and Stegun” is invaluable as a reference.
54. Table of Integrals, Series, and Products. “Gradshteyn and Ryzhik” is the best integral table ever. Let the library buy it, but have them keep it in the reference section so you can find it quickly. 
55. Numerical Recipes. If you want to solve the equations of the Hodgkin-Huxley model, you need to program a computer. This book is great for finding the needed numerical methods.
56. Numerical Methods that Work. Forman Acton’s book is more chatty than Numerical Recipes, but full of insight.
57. Machines in our Hearts. Chapter 7 of IPMB examines the heart. Read this history of pacemakers and defibrillators to put it all in perspective.
58. Cardiac Electrophysiology: From Cell to Bedside. This multi-author, multi-edition work contains everything you always wanted to know about the electrical properties of the heart, but were afraid to ask.
59. Cardiac Bioelectric Therapy. Another multi-author collection, with several excellent chapters about the bidomain model.
60. When Time Breaks Down. Art Winfree’s unique analysis of the electrical properties of the heart.
61. Electric Fields of the Brain. Paul Nunez’s book about the electroencephalogram from the perspective of a physicist.
62. Iron, Nature’s Universal Element. Why people need iron and animals make magnets.
63. The Spark of Life. An accessible introduction to electrophysiology and ion channel diseases.
64. Ion Channels of Excitable Membranes. The definitive textbook about ion channels, by Bertil Hille.
65. Voodoo Science. Some of the topics in Section 9.10 of IPMB about possible effects of weak electric and magnetic fields make me yearn for this hard-hitting book by Bob Park.
66. Dynamics: The Geometry of Behavior. Chapter 10 of IPMB covers nonlinear dynamics. This beautiful book introduces dynamics using pictures.
67. From Clocks to Chaos. Leon Glass and Michael Mackey introduce the idea of a dynamical disease.
68. Nonlinear Dynamics and Chaos. Steven Strogatz’s classic; my favorite book about nonlinear dynamics.
69. Mathematical Physiology. An award-winning textbook about applying math to biology.
70. Mathematical Biology. Another big fine textbook for the mathematically inclined.
71. The Geometry of Biological Time. A quirky book by Art Winfree, more wide-ranging than When Time Breaks Down.
72. Data Reduction and Error Analysis for the Physical Sciences. Many of the ideas about least squares fitting discussed in Chapter 11 of IPMB are related to analyzing noisy data.
73. The Fourier Transform and its Applications. The Fourier transform is the most important concept in Chapter 11. Ronald Bracewell’s book is a great place to learn about it.
74. Introduction to Membrane Noise. Louis DeFelice’s book explains how to deal with noise.
75. Naked to the Bone. A historical survey of medical imaging.
76. Medical Imaging Physics. A book by William Hendee and E Russell Ritenour, at a level similar to IPMB but dedicated entirely to imaging. Also see its partner, Hendee's Radiation Therapy Physics.
77. Foundations of Medical Imaging. A big, technical book about imaging.
78. Theoretical Acoustics. Not much biology here, but a definitive survey of acoustics to back up Chapter 13 of IPMB.
79. Physics of the Body. This book discusses many topics, including hearing.
80. Musicophilia. An extraordinary book by Oliver Sacks about the neuroscience of hearing.
81. Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles. My choice for a modern physics textbook, with much information about the interaction of light with matter.
82. The First Steps in Seeing. Robert Rodieck’s incredible book about the physics of vision.
83. The Optics of Life. This masterpiece by Sonke Johnsen walks you through optics, examining all the biological applications. A great supplement to Chapter 14 of IPMB.
84. From Photon to Neuron. A study of light, imaging, and vision.
85. Introduction to Physics in Modern Medicine. Suzanne Amador Kane’s nice introduction to physics applied to medicine, covering many topics in the last half of IPMB.
86. Introduction to Radiological Physics and Radiation Dosimetry. Frank Herbert Attix wrote the definitive textbook about how x-rays interact with tissue, a topic covered in Chapter 15 of IPMB.
87. Radiobiology for the Radiologist. The go-to reference for how cells and tissues respond to radiation.
88. Molecular Biology of the Cell. The classic textbook of cell biology.
89. Radiation Oncology: A Physicists Eye View. Explains how to treat cancer using radiation.
90. The Physics of Radiation Therapy. Faiz Khan’s in-depth study of radiation therapy.
91. The Atomic Nucleus. An classic about nuclear physics, providing background for Chapter 17 of IPMB. You could replace it with one of many modern nuclear physics textbooks.
92. The Immortal Life of Henrietta Lacks. A fascinating study of how a women treated for cancer using radioactivity ended up providing science with an immortal cell line.
93. Strange Glow. How radiation impacts society.
94. The Radium Girls. This book is about women poisoned by radium-containing paint (lip, dip, paint). It reminds us why we study medical physics.
95. Magnetic Resonance Imaging: Physical Properties and Sequence Design. All you need to know about MRI.
96. Principles of Nuclear Magnetic Resonance Microscopy. Paul Callaghan’s view of magnetic resonance imaging.
97. Echo Planar Imaging. Advanced MRI techniques.
98. Biological Physics. IPMB is not strong in covering physics applied to cellular and molecular biology. Here are three great books to fill that gap.
99. Cell Biology by the Numbers. I love the quantitative approach to biology.
100. Physical Biology of the Cell. How physicists view biology. 

Don’t see your favorite listed? Here’s my call to action: Add your recommendations to the comments below.

I didn’t end up going to St. John’s College and studying the Great Books. Instead, I attended a more traditional school, the University of Kansas. I loved KU, and I have no regrets. But sometimes I wonder...

Listmania! IPMB

Amazon used to have a feature called Listmania! You could make a list of up to 40 books that was visible at Amazon's website. Ten years ago I created a Listmania! list related to Intermediate Physics for Medicine and Biology, reproduced below. Because the list is old, it does not include recent books (such as The Optics of Life) or books that I have discovered recently (such as The First Steps in Seeing). To learn about newer books, search this blog for posts labeled “book review.” Amazon has discontinued Listmania!, but you can still find the lists if you look hard. I miss it.

If you are interested in what I read for pleasure, look here.

Enjoy!

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Intermediate Physics for Medicine and Biology
Bradley J. Roth
The list author says: “Books that are cited by the 4th edition of Intermediate Physics for Medicine and Biology. These are some of the best biological and medical physics books I know of, and are books that have been useful to me during my career.”

Intermediate Physics for Medicine and Biology, 4th edition (Biological and Medical Physics, Biomedical Engineering) All the books listed below are cited in the 4th Edition of Intermediate Physics for Medicine and Biology, written by Russ Hobbie and me.

Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables [Applied Mathematics Series 55] A math handbook that has everything you'll ever need to know.

The 2nd Law: Energy, Chaos, and Form (Scientific American Library Paperback) I love this coffee table book about the second law of thermodynamics.  A painless way to introduce yourself to the subject.

Introduction to Radiological Physics and Radiation Dosimetry Classic in the Medical Physics field.

The Essential Exponential! (For the Future of Our Planet) This book explains why we devoted an entire chapter of Intermediate Physics for Medicine and Biology to the exponential function.

Physics With Illustrative Examples From Medicine and Biology: Mechanics (Biological and Medical Physics, Biomedical Engineering) A classic textbook.

Physics With Illustrative Examples From Medicine and Biology: Electricity and Magnetism (Biological and Medical Physics, Biomedical Engineering) The second edition of the book has much the same content as the first, but the quality of the printing and illustrations is vastly improved.

Physics With Illustrative Examples From Medicine and Biology: Statistical Physics (Biological and Medical Physics, Biomedical Engineering) Benedek and Villars were pioneers in biological and medical physics textbooks.

Random Walks in Biology The best book about the role of diffusion in biology that I know of.

Foundations of Medical Imaging Fine book to study imaging algorithms.

Introduction to Membrane Noise Great book on a little-known topic.

Air and Water One of my favorites. Written by a physiologist with an interest in physics (as opposed to Hobbie and I, who are physicists interested in physiology).

Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles My favorite modern physics textbook.

The Feynman Lectures on Physics (3 Volume Set) (Set v) What physics list could be complete without Feynman?

From Clocks to Chaos Excellent book to learn the biological and medical applications of chaos.

The Machinery of Life Wonderful picture book.  Great way to visualize the relative sizes of biological objects.

Bioelectricity and Biomagnetism Good, thick tome on bioelectricity.

Textbook of Medical Physiology The classic physiology textbook.

Radiobiology for the Radiologist Great place to learn about the biological effects of radiation.

Medical Imaging Physics Standard textbook in medical physics. Hendee is a pioneer in the field.

Ion Channels of Excitable Membranes, Third edition The bible for information about ion channels.

Machines in Our Hearts: The Cardiac Pacemaker, the Implantable Defibrillator, and American Health Care Learn about the history of pacemakers and defibrillators.

The Physics of Radiation Therapy The place to go to learn about radiation therapy.

Bioelectromagnetism: Principles and Applications of Bioelectric and Biomagnetic Fields Fine textbook on bioelectricity.

Powers of Ten (Revised) (Scientific American Library Paperback) Classic work describing how the world looks at different length scales. Required reading by anyone interested in science.

Electric Fields of the Brain: The Neurophysics of EEG, 2nd edition Great way to learn about the physics of the electroencephalogram.

Bioelectricity: A Quantitative Approach Standard textbook for a class in bioelectricity.

Numerical Recipes 3rd edition: The Art of Scientific Computing My go-to book on numerical methods.

Electricity and Magnetism (Berkeley Physics Course, Vol. 2) Best introduction to electricity and magnetism I know. Part of the great Berkeley Physics Course.

Statistical Physics: Berkeley Physics Course, Vol. 5 Great intuitive introduction to statistical mechanics.  Part of the Berkeley Physics Course.

Div, Grad, Curl, and All That: An Informal Text on Vector Calculus (Fourth edition) Need a little review of vector calculus? This is the place to find it.

Scaling: Why is Animal Size so Important? Great book on biological scaling.

How Animals Work Great physiology book. Quirky, but fun.

Nonlinear Dynamics And Chaos: With Applications To Physics, Biology, Chemistry, And Engineering (Studies in Nonlinearity) Best book for a first course in nonlinear dynamics.

Life in Moving Fluids: The Physical Biology of Flow (Princeton Paperbacks) Best book I know of on biological fluid dynamics. Not too mathematical, but full of insight. I recommend all of Vogel's books.

Vital Circuits: On Pumps, Pipes, and the Workings of Circulatory Systems Great for understanding the fluid dynamics of the circulatory system.

Lady Luck: The Theory of Probability (Dover Books on Mathematics) I often find probability theory boring, but not this book. An oldie but goodie.

The Geometry of Biological Time (Interdisciplinary Applied Mathematics) Classic by Art Winfree, who was a leading mathematical biologists.  Be sure to get the 2nd edition.

When Time Breaks Down: The Three-Dimensional Dynamics of Electrochemical Waves and Cardiac Arrhythmias Winfree's classic on the nonlinear dynamics of the heart.

Cardiac Electrophysiology: From Cell to Bedside, 4e Comprehensive reference on cardiac electrophysiology.

The Machinery of Life

The Machinery of Life,
by David Goodsell.

In the very first section of the 5th edition of Intermediate Physics for Medicine and Biology (Sec. 1.1), Russ Hobbie and I discuss “Distances and Sizes.”

In biology and medicine, we study objects that span a wide range of sizes: from giant redwood trees to individual molecules. Therefore, we begin with a brief discussion of length scales.

At the end of this section, we conclude

To examine the relative sizes of objects in more detail, see Morrison et al. (1994) or Goodsell (2009).

I have talked about the book Powers of Ten by Morrison et al. previously in this blog. I have also mentioned David Goodsell’s book The Machinery of Life several times, but until today I have never devoted an entire blog entry to it.

In the 4th edition of IPMB, Russ and I cited the first edition of The Machinery of Life (1998), and that is the edition that sits on my bookshelf. When preparing the 5th edition, we updated our references, so we now cite the second edition of Goodsell's book (2009). Is there much difference between the two? Yes! Like when Dorothy left Kansas to enter Oz, the first edition is all black and white but the second edition is in glorious color. And what a difference color makes in a book that is first and foremost visual. The second edition of The Machinery of Life is stunningly beautiful. It is not just a colorized version of the first edition; it is a whole new book. Goodsell writes in the preface

I created the illustrations in this book to help bridge this gulf and allow us to see the molecular structure of cells, if not directly, then in an artistic rendition. I have included two types of illustrations with this goal in mind: watercolor paintings which magnify a small portion of a living cell by one million times, showing the arrangement of molecules inside, and computer-generated pictures, which show the atomic details of individual molecules. In this second edition of The Machinery of Life, these illustrations are presented in full color, and they incorporate many of the exciting scientific advances of the 15 years since the first edition.

As with the first edition, I have used several themes to tie the pictures together. One is that of scale. Most of us do not have a good concept of the relative sizes of water molecules, proteins, ribosomes, bacteria, and people. To assist with this understanding, I have drawn the illustrations at a few consistent magnifications. The views showing the interiors of living cells, as in the Frontispiece and scattered through the last half of the book, are all drawn at one million times magnification. Because of this consistent scale, you can flip between pages in these chapters and compare the sizes of DNA, lipid membranes, nuclear pores, and all of the other molecular machinery of living cells. The computer-generated figures of individual molecules are also drawn at a few consistent scales to allow easy comparison.

I have also drawn the illustrations using a consistent style, again to allow easy comparison. A space-filling representation that shows each atom as a sphere is used for all the illustrations of molecules. The shapes of the molecules in the cellular pictures are simplified versions of these space-filling pictures, capturing the overall form of the molecule without showing the location of every atom. The colors, of course, are completely arbitrary since most of these molecules are colorless. I have chosen them to highlight the functional features of the molecules and cellular environments.

I have often wondered how much molecular biology a biological or medical physicist needs to know. I suppose it depends on their research specialty, but in general I believe a physicist who has read and understood The Machinery of Life has most of what you need to begin working at the interface of physics and biology: An understanding of the relative scale of biological objects, an overview of the different types of biological molecules and their structures and functions, and a visual sense of how these molecules fit together to form a cell. To the physicist wanting an introduction to biology on the molecular scale, I recommend starting with The Machinery of Life. That’s why it was included in my ideal bookshelf.

Goodsell fans might enjoy visiting his website: http://mgl.scripps.edu/people/goodsell. There you can download a beautiful poster of different proteins, all drawn to scale. There are many other illustrations and publications. Enjoy!

Distances and Sizes

One of the additions that Russ Hobbie and I made to the 4th edition of Intermediate Physics for Medicine and Biology is an initial section in Chapter 1 about Distances and Sizes.

In biology and medicine, we study objects that span a wide range of sizes: from giant redwood trees to individual molecules. Therefore, we begin with a brief discussion of length scales.

The Machinery of Life,
by David Goodsell.

We then present two illustrations. Figure 1.1 shows objects from a few microns to a few hundred microns in size, including a paramecium, an alveolus, a cardiac cell, red blood cells, and E. coli. Figure 1.2 contains objects from a few to a few hundred nanometers, including HIV, hemoglobin, a cell membrane, DNA, and glucose. Many interesting and important biological structures were left out of these figures.

I admit that our figures are not nearly as well drawn as, say, David Goodsell’s artwork in The Machinery of Life. But, I enjoy creating such drawings, even if I am artistically challenged. So, below are two new illustrations, patterned after Figs. 1.1 and 1.2. Think of them as supplementary figures for readers of this blog.

FIGURE 1.1½. Objects ranging in size from 1 mm down to 1 μm.
(a) Human hair, (b) human egg, or ovum, (c) sperm,
(d) large myelinated nerve axon, (e) skeletal muscle fiber,
(f) capillary, (g) yeast, and (h) mitochondria.

FIGURE 1.2½. Objects ranging in size from 1 μm down to 1 nm.
(a) Ribosomes, (b) nucleosomes, (c) tobacco mosaic virus,
(d) antibodies, and (e) ATP.

Powers of Ten.

When you combine these figures with those in IPMB, you get a nice overview of the important biological objects at these spatial scales. Two things you do not get are a sense of their dynamic behavior (e.g., Brownian motion) at the microscopic scale, and an appreciation for the atomic nature of all objects (you could not detect single atoms in Fig. 1.2½, but they lurk just below the surface; ATP consists of just 47 atoms).

If you like this sort of thing, you will love browsing through The Machinery of Life or Powers of Ten.