The words Boundary and Life are surprisingly synonymous with each other. One separates two things distinctly, and the other separates a physical entity with biochemical reactions from physical entities without such capabilities.
The Earth is inside the boundary of the goldilocks zone, making it hospitable for life to evolve from the chemical soup formed during its formation. The atmosphere surrounding it gave rise to enormous types of environments, making up the biosphere. Finally, the most important of the boundaries is the plasma membrane, the very reason life has evolved to such complex forms and not be a mass of gooey formless mass floating around.
We can think of the Plasma membrane as a sci-fi toll plaza or a multi-modal transportation hub constantly on the move.
Like on a larger scale, how different people use different ways of transportation to reach their destination, complete a task or ensure a smooth flow of logistics and communication. The cells are mini-living cities in their regard, requiring an extremely efficient way to transport different molecules in different ways or communicate with other cells, capture materials, or expel waste. The Plasma membrane evolved efficiently to fulfill these needs.
The Plasma membrane has often been termed a structure of contradiction mainly because of the theory regarding its origin and the properties it possesses. The cell membrane's origin is unique as it is a structure made up of fatty acids, which are present in the lipid bilayer, more about it in the below paragraphs. These fatty acids aren't stable in the presence of ions, charged elements like sodium or chloride ions.
How are they so strong and stable? The reason can be traced back to the first biomolecules that originated from the chemical soup. Amino acids and later the RNA, bonded with the fatty acids stabilizing them to form the first proto membranes supporting the various theories linked to it like replication of life, the inclusion of Mitochondria as an organelle into the cell, and most importantly, the RNA world theory.
The cell membrane is mentioned from the inception of the cell theory (the 1700s) as a membrane impermeable to water allowing specific molecules to pass through them. Their exact structure remained a mystery till the proposal of various models like the 1920 Garter and Grendel model, which suggested it was a lipid bilayer, a membrane made up of two layers of lipid having hydrophobic and hydrophilic ends. Later was the 1935 Davson and Danielli model, which included proteins as a part of the plasma membrane and termed it a sandwich of lipids layers with proteins. Further research gave rise to the most widely accepted "Fluid mosaic model " by Singer and Nicholson, emphasizing its fluid nature and the proteins present in it.
The Plasma membrane often overshadows the functions of other cell organelles by performing a number of tasks.
These include repairing cells, regulating the movement of ions and other essential molecules, transporting water using channel proteins like aquaporin, exhibiting adhesion - sticking to other cells, endocytosis - ingestion of required materials, exocytosis - moving large molecules or waste material out of the cells and use of Cell signaling, a unique form of communication on the molecular level which needs an entirely different blog of its own.
The plasma membrane has been an object of interest for researchers as it holds answers regarding the origin and evolution of life into such complex forms that exist today. It has been the forerunner in inspiring new technologies in medicine and nanotechnology, like membrane-based drug delivery systems and bio-interfaces that may revolutionize medical devices or even pave a path for the creation of androids.
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