At the dawn of life, heat may drive cell division

Elegant ballet Proteins enable modern cells to replicate themselves. During cell division, structural proteins and enzymes coordinate the replication of DNA, the division of cytoplasmic contents, and the tightening of the membranes of dividing cells. It is essential to handle these processes correctly, because mistakes can cause the daughter cells to become abnormal or unable to survive.

Billions of years ago, the first self-organizing membrane-like chemicals spontaneously produced from inanimate materials must have faced the same challenge. But it is almost certain that these primitive cells must replicate without relying on large proteins. How they did it is a key question for astrobiologists and biochemists who study the origin of life.

“If you delete all the enzymes in the cell, nothing will happen. They are just inert sacks,” said Anna Wang |, Astrobiologist at the University of New South Wales in Sydney. “They are really stable, that’s the point.”

However, in A recent paper exist Biophysical JournalPhysicist Romain Attal of the French City of Science and Industry and Laurent Schwartz, a cancer biologist at the Paris Public Hospital, developed a series of mathematical equations that simulate an important part of the process that heat alone is enough to drive replication: a primitive cell Split into two.

Attal believes that the chemical and physical processes that are active early in life may be very simple, so thermodynamics alone can play an important role in the beginning of life. He said that the various basic equations he has been studying can clarify some of the rules governing the initial emergence of life.

“The temperature gradient is very important to life,” Attar said. “If you understand a subject, you need to be able to write down its principles.”

Flip fission

For primitive cells to divide themselves without complex protein mechanisms, the process requires physical or chemical drives. “It’s really about stripping cells to their basic functions and thinking,’What are the basic physical and chemical principles, and how can we imitate it without protein?'” Wang said.

When you consider that scientists are still unable to agree on the definition of life in general, and the definition of primitive cells in particular, figuring out these processes becomes more challenging.

Scientists agree that the original cell must have some kind of genetic information that can be passed on to its daughter cells, a kind of metabolism that performs chemical reactions, and a kind of lipid that isolates the metabolism and genetic information from the randomness of the rest of the earth. Plasma membrane. Original soup. Although the external chemical world is inherently random, the partition provided by the lipid membrane can create a low-entropy region.

In order for the original cell to grow before it divides, it must not only increase the volume inside the cell, but also increase the surface area of ​​the surrounding membrane. To create two smaller daughter cells with the same total volume as the parent cell, their membrane requires additional lipids because their surface area is larger relative to their volume. The chemical reactions needed to fuel the synthesis of these lipids will release energy in the form of heat.

When Attal discussed these ideas with Schwartz, he began to wonder whether this energy was enough to drive early cell division. A search of the research literature revealed a study that found that the temperature of the mitochondria (the energy center of the cell that began as symbiotic bacteria billions of years ago) is slightly higher than that of the surrounding cells. Attal wants to know whether this energy difference can be produced in primitive cells and whether it is enough to drive fission.

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