The first thing to define is what is life. I, as a cell biologist, think that the cell is the minimum unit for life, whether that cell is a bacterium or a eukaryotic cell, such as any of our neurons. The cells can grow, reproduce and respond and stay in front of the changes, that's what we call being alive. To achieve this they have to be able to produce energy. A cell can carry out all these functions if its components are confined within a space, because otherwise the molecules would disperse, they could not be found and they would not be able to carry out all those essential processes for life, such as the duplication of genetic material during cell division.
If we go to the origin of life, we can delve more deeply into the answer to your question. There is no single theory to explain this origin, but all of them mention at some point the existence of membranes in the first cells. And that means we can not imagine the existence of life without those membranes.
The cell membrane that is also called plasma membrane is a structure that surrounds the entire cell, encloses its components and allows the maintenance of a different composition between the inside and the outside of the cell. It is formed by a thin layer of lipids where proteins are inserted. These proteins can create pores or channels that allow the selective and controlled entry and exit of substances that the cell needs to continue functioning. For these channels, for example, glucose enters, one of the main foods for cells.
Only visible with electron microscope
The cell membrane is so small that we can not even see it with an optical microscope, only with an electronic one. And that caused that for a long time, until the invention of the electron microscope, the scientific community described the membrane as an invisible layer that contained everything that forms the cells without ever having observed it.
If the existence of a membrane that surrounds the cell is essential for life, then when the membrane is broken does the cell die? Well that is precisely one of the definitions we use in biology for cell death. When the plasma membrane breaks, the components go outside and the cell can no longer maintain its functions. In addition, that is precisely what some toxins produced by bacteria do. For example, hemotoxin, produced by a staphylococcus, is capable of breaking the membrane of some of the blood cells.
Research has shown that the formation of a compartment separated from the environment by a membrane is one of the most conserved attributes in living beings. And that leads us to think that it is because it is also one of the attributes that had the first living beings that existed. So the answer to the question would be that, as we know it, life itself would need a cell membrane or some kind of structure that allows the containment of molecules.
Patricia Boya She is a cell biologist and a scientific researcher at the Center for Biological Research of the CSIC.
Question done via email by Gerardo Lozano Chapa
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