LEQ: How does the structure of the plasma membrane allow it to function as a regulatory structure and/or protective barrier for a cell? Cell Membranes Pages 79 to 81

Fig. 7-2 Hydrophilic head WATER Hydrophobic tail WATER Phosopholipids Hydrophillic (polar) heads point out toward water Hydrophobic (nonpolar) tails point inward away from water

Fig. 7-3 Phospholipid bilayer Hydrophobic regions of protein Hydrophilic regions of protein

Fluid Mosaic Model The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it ◦ Mosaic – surface made of small fragments ◦ Fluid – molecules can drift in the membrane

Fig. 7-7 Fibers of extracellular matrix (ECM) Glyco- protein Microfilaments of cytoskeleton Cholesterol Peripheral proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Carbohydrate

Lipid bilayer – regulates what enters and exits the cell; said to be selectively permeable Carbohydrates – attach to lipids and/or protein; cell identification tags Cholesterol – maintains membrane fluidity / stability Cell Membranes

Six major functions of membrane proteins: ◦ Transport ◦ Enzymatic activity ◦ Signal transduction ◦ Cell-cell recognition ◦ Intercellular joining ◦ Attachment to the cytoskeleton and extracellular matrix (ECM) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 7-9 (a) Transport ATP (b) Enzymatic activity Enzymes (c) Signal transduction Signal transduction Signaling molecule Receptor (d) Cell-cell recognition Glyco- protein (e) Intercellular joining (f) Attachment to the cytoskeleton and extracellular matrix (ECM)