Why Elephants Have Bigger Bones and Other Mysteries of Biophysics

Why Elephants Have Bigger Bones and Other Mysteries of Biophysics

Before the 1970s, about 25,000 premature babies died each year from a condition called respiratory distress syndrome. Patrick Bouvier Kennedy, the infant child of President John F. Kennedy and Jacqueline Kennedy, was one of them. But in the decades that followed, that number dropped to just 400 deaths a year.

“So how did this massive decline happen?” Raghuveer Parthasarathy asked last week during a virtual Harvard Science Book Conference presented by the university’s Science Division, Cabot Science Library and Harvard Bookstore. “The answer,” he continued, “has to do with lungs and fluids.”

Or really, the answer came from the fusion of lung and fluid science with the relatively young field of biophysics, the child of biology and physics and the subject of Parthasarathy’s new book, “Si Simple a Beginning: How Four Physical Principles Shape Our Living World”. .” In it, Parthasarathy explores how universal physical rules shape all life on Earth, answering questions such as why elephants need such big bones, how birds fly and bacteria squirm, and why distress syndrome respiratory decreased so rapidly.

Think of the lungs as sort of balloons covered in watery mucus, said Parthasarathy, a physics professor at the University of Oregon. They have the volume of a few tennis balls, but the surface area of ​​an entire tennis court due to their numerous airways and tiny expandable air sacs. These sacs, called alveoli, are where oxygen and carbon dioxide are exchanged as we inhale and exhale.

All this fabric is soaked with water. And, because of one of the physical rules governing our universe, water molecules hate being on surfaces – which is the problem. Since the water molecules all try to get as far away from the surface of, say, a pond as possible, this creates enough tension for insects, like water striders, to glide over it. But when these molecules detach from the surface of a premature baby’s lungs, they can collapse their tiny air sacs.

And yet soap, said Parthasarathy, loves surfaces. To demonstrate this, he floated a paperclip above a glass of water – a feat made possible by the surface tension of water. Parthasarathy then poured dish soap; the surface tension has disappeared; and the trombone sank. So, he said, all premature babies needed was a little soap — or rather, the soap-like molecule called surfactant — that all humans make after 26 weeks of fetal development. This solution, says Parthasarathy, was not complicated. Once doctors understood the physics of liquids, they were able to understand the biology of respiration.

“It’s an exquisite dance to find out what details matter and what inspirations explain the problem,” said Philip Nelson, a biophysicist at the University of Pennsylvania, who joined the virtual conversation to discuss Parthasarathy’s new book.

Both lamented the lack of awareness in the field of biophysics. (Parthasarathy said he recently gave a talk titled “Biophysics Exists.”) The duo also discussed the four physical principles Parthasarathy chose to include in his book. The first, self-assembly, refers to the innate ability of things – like materials, molecules or cells – to build complex patterns (surfactants are one example). Proteins fold into origami shapes. Soap bubbles and fly eyes alone form beautiful, intricate structures. “Biology is the master of self-assembly,” Parthasarathy said.

The other three principles are: the regulatory circuits – or things, like DNA, that gather information and make decisions; predictable randomness – Parthasarathy’s favorite and the reason why we can predict someone’s height by analyzing hundreds of genes (but we can’t say exactly which genes are responsible); and scaling. Scaling is why elephants need much bigger bones than sparrows. Gravity, a physical law, exerts pressure on an elephant’s mass. Large bones help the animal to withstand this pressure.

These four principles could explain why life, from microscopic bacteria to bulky elephants, takes on such diverse forms. But humans can also manipulate these rules to build tools. For example, scientists can now perform gene sequencing with an untangled string of DNA.

“It sounds like total sci-fi,” Nelson said, “but now you can buy it.” And, he continued, “Many of us are alive today thanks to a vaccine of a class that did not exist a few years ago. And many of these ideas came from nature.

Parthasarathy, who illustrated his book with his own watercolors of “exquisite” biology, also answered questions from the virtual audience about, for example, why he had chosen only four principles (felt more like “too much mis- melodrama,” he said), whether evolution could be another unifying principle (it’s more of a way to navigate the rules, he said), and whether free will exists if physical laws govern all life. This question kept him awake at night, Parthasarathy said. “I pretty much agree with everything in our consciousness that has to do with physical ownership. In other words, having no free will.

Another audience member asked if biophysics could explain so much about biology, if life would still be a mystery a decade from now. “Yes,” Parthasarathy said. We still don’t understand how organs grow to different sizes, how embryos form, or why our two arms end up being the same length.

“We have a lot of questions like that,” he said. “We have plenty to take care of.”

#Elephants #Bigger #Bones #Mysteries #Biophysics

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