Test 2 - Chapter 4 Cell Membrane Structure and Function I....

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Chapter 4 Cell Membrane Structure and Function I. The Cell Membrane a. The cell membrane is usually the outermost barrier of the cell. i. An exception to this is found in cells which have a cell wall. 1. Plants—cellulose 2. Fungi—chitin 3. Bacteria—chitin plus proteins b. The cell wall is mainly for structural support and protection. i. It usually doesn’t act as a barrier to molecules. II. The Plasma Membrane a. The plasma membrane contains the cell but still allows the cell to interact with the environment. b. Fig. 4-1 c. The plasma membrane functions: i. Isolate the cell environment ii. Regulate exchange between inside and outside iii. Communicate with other cells iv. Identify the cell type d. Plasma membrane is the membrane at the boundary of every cell that acts as a selective barrier, thereby regulating the cell’s chemical environment. i. Membranes are made primarily of lipids. ii. Phospholipids are molecules which can form membranes naturally iii. Pg. 58 e. Cell membranes are phospholipid bilayers i. Evidence: the phospholipid content of red blood cells is just enough to cover the cell with two layers. ii. The red blood cell has no internal membranes. III. Biological Membranes a. Biological membranes contain proteins i. Evidence: membranes isolated from red blood cells contain proteins in addition to lipids b. Singer and Nicolson: Fluid Mosaic Model i. Fig. 4.1 IV. Fluidity a. Fluidity in membranes means there is lateral two-dimensional movement of the lipids and some proteins in the plane of the membrane. b. However, transverse (flip-flop) across the membrane is rare. c. Movement of phospholipids i. Lateral movement 10 7 times per second ii. Flip flop ~ once per month V. Mosaic a. Mosaic aspects of membranes means that there are proteins interspersed within the lipid bilayer VI. Functions of Membrane Proteins: a. Transport proteins i. Channel proteins—pores ii. Carrier proteins—selective revolving doors b. Receptors c. Cell to cell recognition
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i. Some of the recognition keys of the surface of cells are glycoproteins
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This note was uploaded on 05/04/2010 for the course BIOL 1001 taught by Professor Minor during the Fall '08 term at LSU.

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Test 2 - Chapter 4 Cell Membrane Structure and Function I....

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