110105 - BE.342/442 Tuesday, November 1, 2005 Topic: Lipids...

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BE.342/442 Tuesday, November 1, 2005 Topic: Lipids as Building Materials We’ve discussed amino acids as building blocks of protein-based materials and nucleic acids as building blocks of DNA-based materials. Today we’ll discuss lipids as building blocks of membranes. Next, we’ll discuss sugars as building blocks of cellulose, starch, and other materials. Cell Membranes Membranes are ubiquitous in living systems and absolutely crucial to establish an isolated environment and entity. Individual lipid molecules are ~2 nm in size and cannot form covalently linked polymers, but they are able to form very stable and ordered assemblies. In solution, lipids self-assemble into micelles, vesicles, nano- and micro-tubules, liposomes, organized tubular clusters, and reverse micelles. These self-assembled structures can then be functionalized, metalized, and modified for a number of applications. Membranes are present both around the cell and around organelles such as the nucleus, endosomes, mitochondria, the Golgi apparatus, the endoplasmic reticulum, and others. Biological membranes contain bilayers of lipids, with the polar heads facing the solution on the inner and outer side of the membrane, and the hydrophobic tails aggregated on the inside. Six cells contain a mole (Avogadro’s number) of lipids! Proteins can be fully or partially embedded in the membrane. The outside surface of cell membranes is typically rich in glycoproteins, which present sugar groups on the surface of the cell to identify its phenotype (for example, blood types). The inside surface is typically rich in lipoproteins, or proteins are linked to hydrophobic tails, which anchor them to the cell membrane. Other important membrane proteins include the
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This note was uploaded on 11/11/2011 for the course BIO 20.410j taught by Professor Rogerd.kamm during the Spring '03 term at MIT.

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110105 - BE.342/442 Tuesday, November 1, 2005 Topic: Lipids...

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