The modern concept of a cell membrane is drawn from a long history of the science of cell membranes.
This lesson explores how our idea of a membrane surrounding a cell has changed over history, as well as our current understanding of how it functions.
The Earliest Cell Membrane Ideas
The tiniest unit of our biological selves, a cell, filled with cell fluid and surrounded by a thin membrane. This membrane keeps our cells intact, acts as a protective barrier, and is fluid enough to allow quite a bit of cell flexibility.But there was a time when scientists weren’t sure whether there even was a cell membrane.
Did cells just congeal together, held by some other force? If a cell membrane existed, how did cells transport things in an out of the cell itself? There isn’t one single person who discovered the cell membrane; rather, a number of people were able to describe the membrane in a long, rich history of cell membrane science.The story of the cell membrane as we understand it today begins in the seventeenth century, with the invention of the microscope by Robert Hooke. The very existence of cells was illuminated by the observation of the microscopic world. But it would take another two hundred years, in the early 1800s, until the boundary of the cell was thoroughly investigated.
By 1837, scientists Theodor Schwann and Matthias Schleiden had compared plant and animal cell boundaries. They described how the components of animal cells were limited in their movement by some kind of invisible barrier. What was this barrier? Was it a cell membrane of some sort?Cell membranes weren’t popular.
Many scientists thought that cells were just held together by surface tension, with the pulling of cell liquid together by adhesive forces. And a membrane was invisible, even under the microscope. The idea of an external boundary didn’t catch on again in earnest until the turn of the 20th century.
Who Discovered The Cell Membrane?
Building on a long history of back-and-forth between invisible cell membranes and nonexistent cell membranes, the Dutch scientists E.
Gorter and F. Grendel made a genius breakthrough in 1925. They determined that the ratio of lipids, or fatty molecules that are insoluble in water, to the surface area of a cell was 2:1 in favor of lipids. It appeared that there were twice the amount of lipids needed to coat the surface of the cell.
Or, Gorter and Grendel postulated, the cell membrane was made up of a bilayer of lipids, two layers sandwiched together with the water-avoidant hydrophobic tails of the lipids touching one another. On either end of the lipid bilayer, water-loving hydrophilic heads of the lipids touched the internal cellular fluid and the external cellular fluid.Gorter and Grendel’s bilayer idea was revolutionary; they are credited with the first description of the cell membrane as a bilayer of lipids, and therefore, the discoverers of the cell membrane as we know it today.The back and forth about the nature of this phospholipid bilayer, a double layer of lipids sandwiched together and surrounding the cell, went on for several years. No one could quite figure out how this membrane functioned, even though it became increasingly clear that a membrane did exist.Studies through the 1940s on through the 1960s focused on how ions, or charged particles, charged compounds like sodium and potassium, moved across a cell’s membrane. Evidence was building that the phospholipid bilayer had to have something other than lipids within it in order to allow big molecules in and out of the cell.
The Fluid Mosaic Cell Membrane Model
Several studies in the 1960s pointed to the presence of proteins in the phospholipid bilayer, and by 1972, the scientists Singer and Nicolson developed a model that allowed the cell membrane to incorporate both of these biomolecules. This model, known as the fluid mosaic model, has been accepted since the 1970s for its strength in explaining how large and small molecules pass through the cell membrane. Take a look at the image below.
|The Grendel will not approach Hroogar’s throne. The