Lecture 7 - Lipids, Membranes, and the First Cells The...

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the First Cells The plasma membrane is a layer of molecules, mostly lipids, that surrounds a cell, separating the life inside the cell from the external environment and regulating passage of molecules and ions into and out of the cell. • The development of a plasma membrane around a self-replicator created the first cell. • Lipids, the building blocks of membranes, likely existed in the prebiotic soup. Lipids have a major hydrocarbon component and are mostly nonpolar and hydrophobic ( Figure 6.3 ). • A fatty acid is a hydrocarbon chain bonded to a carboxyl (COOH) group. Fatty acids and isoprene hydrocarbons are key building blocks for lipid synthesis in organisms ( Figure 6.3b ). Lipids are defined by solubility rather than by chemical structure, so their structures vary widely ( Figure 6.4 ). Steroids (e.g., cholesterol) have a four-ring structure made from isoprene subunits. Phospholipids consist of a 3-carbon glycerol linked to a phosphate group, PO 4 2– , and two isoprene chains or two fatty acids. • A
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This note was uploaded on 12/06/2009 for the course BIO 225 taught by Professor Pavgi during the Spring '08 term at University of Michigan.

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Lecture 7 - Lipids, Membranes, and the First Cells The...

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