BIO 1000 Lecture Notes - Lecture 12: Lipid Bilayer, Electron Microscope, James Danielli

• School: St. John's University
• Department: Biology
• Course: BIO 1000
• Professor: Jai Dwivedi

Document Summary

The main macromolecules in membranes are lipids and proteins, but carbohydrates are also important. Phospholipids and most other membrane constituents are amphipathic molecules. Amphipathic molecules have both hydrophobic regions and hydrophilic regions. The arrangement of phospholipids and proteins in biological membranes is described by the fluid mosaic model. Membrane models have evolved to fit new data. Models of membranes were developed long before membranes were first seen with electron microscopes in the 1950s. In 1915, membranes isolated from red blood cells were chemically analyzed and found to be composed of lipids and proteins. In 1925, e. gorter and f. grendel reasoned that cell membranes must be a phospholipid bilayer two molecules thick. The molecules in the bilayer are arranged such that the hydrophobic fatty acid tails are sheltered from water while the hydrophilic phosphate groups interact with water. Actual membranes adhere more strongly to water than do artificial membranes composed only of phospholipids.