I fetched out a cruet of oil and dropped a little of it on the water. In 1774, Franklin observed the effects of oil on a surface of water and found that the oil does not mix with the water but rather spreads over the water’s surface to create a thin film:

Our scientific understanding of membranes began with the American statesman Benjamin Franklin. Yes, it does restrict many molecules from entering (or leaving) the cell, but it is also designed so that some molecules can very quickly move through the membrane, and thus enter or leave the cell with ease. We now understand that the plasma membrane is a very dynamic part of the cell and that is much more than just a barrier. From the 17 th century until around the 1960s, the outer membrane of cells was thought to be a simple passive barrier. Although it was too thin for them to see with simple light microscropes, scientists called this outer wrapping a membrane (in Latin, membrana), which means a thin layer of skin or tissue. Understanding Scientific Journals and Articlesįrom the time cells were first discovered in the mid-1600s, scientists knew that there must be some sort of outer wrapping around the cell to hold the contents of the cell together.Using Graphs and Visual Data in Science.Scientists and the Scientific Community.Scientific Notation and Order of Magnitude.The Case of the Ivory-billed Woodpecker.Santiago Ramón y Cajal and Camillo Golgi.Factors that Control Earth's Temperature.Plates, Plate Boundaries, and Driving Forces.Solutions, Solubility, and Colligative Properties.

Y-Chromsome and Mitochondrial DNA Haplotypes.Absorption, Distribution, and Storage of Chemicals.

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