Plasma Membrane: Structure and Function Bellwork Last unit you learned about the macromolecule phospholipid. Phospholipids are amphipathic. Write down what that means. Objectives Describe the function of the plasma membrane Distinguish between peripheral, integral, and transmembrane proteins Explain the structure of the plasma membrane based on the Fluid Mosaic Model Explain the role carbohydrates play in cell to cell recognition Key Terminology Amphipathic Peripheral protein Integral protein Transmembrane protein Fluid Mosaic Model Glycoprotein Glycolipid Function Acts as a barrier separating the internal environment of the cell from the external environment Selectively permeable controlling what moves in and out of the cell All cells have outer membrane, the plasma membrane Unique Structure Lipid bilayer composed of phospholipids polar (hydrophillic) heads facing the internal and external aqueous environment nonpolar (hydrophobic) tails facing inward towards each other Phospholipids amphipathic have a polar and nonpolar region of the molecule External Internal Think-Pair-Share If you compare the cell to a city, what object in the city would be analogous to the cell membrane? Explain your reasoning. 3 Proteins in the Phospholipid Bilayer Integral Proteins Peripheral Proteins embedded in the membrane into the hydrophobic core attached to the surface of the membrane, often to integral proteins Transmembrane Proteins go completely across the membrane with ends sticking out of interior and exterior Proteins associated with the Plasma Membrane Fluid Mosaic Model 1972, J. Singer and G. Nicholson proposed the fluid mosaic model Phospholipid bilayer is envisioned as fluid with a mosaic of embedded proteins floating in the bilayer Membrane fluidity Membrane lipids and proteins move laterally within the membrane Lipids move quicker than proteins Think-Pair-Share Speculate why lipids do not move across the membrane? 3 Function of Plasma membrane Proteins Transport- move ions and polar molecules across the hydrophobic barrier Enzymatic activity-catalyze chemical reactions Receptors- bind chemical signals like hormones Membrane Proteins Think-Pair-Share In the grocery store, different items have a bar code. What is the purpose of that bar code? 3 Cell to Cell Recognition Like bar codes, the cell membrane has a way to identify different cell types by surface molecules The key molecule is most often carbohydrates Usually branched Attached to either proteins (glycoproteins) or lipids (glycolipids) Cell to Cell Recognition Snapshot Write a snapshot in 25 words or less of what you learned today PROPERTY OF PIMA COUNTY JTED, 2010 18