Lec4.2011 - BIO320CELLBIOLOGY READING Alberts Chapter 10 Lecture 4 The Structure and Function of the Membranes I Introduction A B

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BIO 320 – CELL BIOLOGY READING: Alberts Chapter 10. Lecture 4: The Structure and Function of the Membranes 1/27/11 Outline for the Reading I. Introduction A. The plasma membrane is the outer boundary of the cell. B. Plasma membranes of all cell types exhibit characteristic trilaminar appearance in electron  micrographs. II. An Overview of Membrane Functions A. Protective Physical  Barrier B. Selective Chemical  Barrier C. Encapsulates Specialized Compartments D. Support Two Dimensional Diffusion  III. The Chemical Composition of Membranes A. Membrane composition: 1. The lipid and protein components of membranes are bound together by non-covalent  forces. 2. In addition to lipids and proteins, membranes also contain carbohydrates.  1. Protein/lipid ratios vary considerably among different membrane types.  A. Membrane lipids: 1. Membrane lipids are amphipathic . 2. There are three main types of membrane lipids: a. Phospholipids (most are Phosphoglycerides) are diacylglycerides with small functional head  groups linked to the glycerol backbone by phosphate ester bonds.  b. Sphingolipids are ceramides formed by the attachment of sphingosine to fatty acids. c. Glycolipids have a carbohydrate attached to the lipid.   d Cholesterol is a smaller and less amphipathic lipid that is only found in animals. A. The Nature and Importance of the Lipid Bilayer: 1. Membrane lipid composition is characteristic of specific membranes.  2. Lipids give membranes the ability to fuse, form networks, and separate charge. 3. Lipid bilayers assemble spontaneously in aqueous solutions.  A. Membrane Carbohydrates: 1. Membranes contain carbohydrates covalently linked to lipids and proteins on the extracellular  surface of the bilayer. 1. Glycoproteins are short, branched carbohydrates covalently attached to membrane proteins.
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4.  Glycolipids have larger carbohydrate chains covalently attached to membrane lipid.   A. Membrane Proteins: 1. Membrane proteins attach to the bilayer asymmetrically, giving the membrane a distinct 
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This note was uploaded on 02/27/2011 for the course BIO 320 taught by Professor Staff during the Spring '08 term at University of Texas at Austin.

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Lec4.2011 - BIO320CELLBIOLOGY READING Alberts Chapter 10 Lecture 4 The Structure and Function of the Membranes I Introduction A B

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