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This chapter presents the following content: Cellular membranes are fluid mosaics of lipids and proteins, membranes structure results in selective permeability, passive transport in diffusion of a substance across a membrane with no energy investment, active transport uses energy to move solutes against their gradients, bulk transport across the plasma membrane occurs by exocytosis and endocytosis. | Membrane Structure and Function Chapter 7 Overview: Life at the Edge The plasma membrane is the boundary that separates the living cell from its surroundings The plasma membrane exhibits selective permeability, allowing some substances to cross it more easily than others © 2011 Pearson Education, Inc. Concept 7.1: Cellular membranes are fluid mosaics of lipids and proteins Phospholipids are the most abundant lipid in the plasma membrane Phospholipids are amphipathic molecules, containing hydrophobic and hydrophilic regions The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it © 2011 Pearson Education, Inc. For the Cell Biology Video Structure of the Cell Membrane, go to Animation and Video Files. Figure 7.2 Hydrophilic head Hydrophobic tail WATER WATER Figure 7.2 Phospholipid bilayer (cross section). Figure 7.3 Phospholipid bilayer Hydrophobic regions of protein Hydrophilic regions of protein Figure . | Membrane Structure and Function Chapter 7 Overview: Life at the Edge The plasma membrane is the boundary that separates the living cell from its surroundings The plasma membrane exhibits selective permeability, allowing some substances to cross it more easily than others © 2011 Pearson Education, Inc. Concept 7.1: Cellular membranes are fluid mosaics of lipids and proteins Phospholipids are the most abundant lipid in the plasma membrane Phospholipids are amphipathic molecules, containing hydrophobic and hydrophilic regions The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it © 2011 Pearson Education, Inc. For the Cell Biology Video Structure of the Cell Membrane, go to Animation and Video Files. Figure 7.2 Hydrophilic head Hydrophobic tail WATER WATER Figure 7.2 Phospholipid bilayer (cross section). Figure 7.3 Phospholipid bilayer Hydrophobic regions of protein Hydrophilic regions of protein Figure 7.3 The original fluid mosaic model for membranes. The Fluidity of Membranes Phospholipids in the plasma membrane can move within the bilayer Most of the lipids, and some proteins, drift laterally Rarely does a molecule flip-flop transversely across the membrane © 2011 Pearson Education, Inc. Figure 7.5 Glyco- protein Carbohydrate Glycolipid Microfilaments of cytoskeleton EXTRACELLULAR SIDE OF MEMBRANE CYTOPLASMIC SIDE OF MEMBRANE Integral protein Peripheral proteins Cholesterol Fibers of extra- cellular matrix (ECM) Figure 7.5 Updated model of an animal cell’s plasma membrane (cutaway view). Figure 7.6 Lateral movement occurs 107 times per second. Flip-flopping across the membrane is rare ( once per month). Figure 7.6 The movement of phospholipids. Figure 7.7 Membrane proteins Mouse cell Human cell Hybrid cell Mixed proteins after 1 hour RESULTS Figure 7.7 Inquiry: Do membrane proteins move? As temperatures cool, membranes switch from a fluid state to a solid state The
