Slide 1Membrane Function, Structure and DynamicsMembrane Function, Structure and DynamicsMembrane Function, Structure and DynamicsMembrane Function, Structure and DynamicsMembrane Function, Structure and DynamicsMembrane Function, Structure and DynamicsMembrane Function, Structure and DynamicsMembrane Function, Structure and DynamicsMembrane Function, Structure and DynamicsMembrane Function, Structure and DynamicsPage 1Membrane Function, Structure and DynamicsLehninger ReadingsChapter 11 pages 371-389At the end of this section you should be able to apply what you learned about lipids in previous lectures in this course and what you learned about proteins and carbohydrates in BMB461 to discussions about the structure and function of membranes. You should be able to explain how interactions between components in the membrane influence the structure and function of the membrane. Finally, you should be able to predict how the properties and functions of the membranes will change as their compositions changes. Student Learning Objectives You should be able to: 1) Tell the "Big Picture" story of how membranes are constructed and how they function.2) Recognize membrane lipids as amphipathic compounds that form lipid bilayers in aqueous media.3) Relate the physical and chemical properties of membrane lipids to their roles in the membrane.4) Describe the functions of membranes in cells and explain how the composition of the membrane and the physical and chemical properties of membrane components relate to those functions.5) Describe the fluid mosaic model of membranes. 6) Identify the location, orientation and structures of typical lipids and proteins in the asymmetric lipid bilayer.7) Define integral, peripheral, and lipid-anchored membrane proteins and recognize each type in terms of its physical and chemical characteristics.8) Interpret hydropathy plots and relate these to the physical and chemical characteristics of membrane proteins.9) Define membrane fluidity and explain how fluidity is governed by fatty acid composition and cholesterol content, relate this to the physical and chemical properties of these molecules, and predict how changes in membrane composition will influence fluidity.10) Define lateral and transverse diffusion and explain the diffusion of lipids and proteins in membranes based on their physical and chemical properties.11) Discuss microdomains in membranes including composition and possible biological roles. 12) Describe membrane fusion and some biological processes that rely on this feature of membranes.Page 2Membrane Function, Structure and Dynamics•Functions of biological membranes.–Regulate what crosses the membrane – they are semipermeable. Transport proteins allow this.–Demarcate cell boundaries and compartments.–Organize complex reactions allowing communication and energy generation. Receptors proteins are important for perceiving signals. The 2D surface increases molecular interactions and increase efficiency.–Break and reseal allowing things like exocytosis and endocytosis.•Common features despite diversity of biological membranes.–Membranes are sheet-like structures 5-8 nm (50-80 Å) thick.–Membrane lipids are amphipathic, i.e., they posses both hydrophobic and hydrophilic components, arranged as lipid bilayers.–Membranes are not covalently assembled but are linked by many noncovalent interactions making the membrane fluid.–Membranes consist of polar lipids and proteins to which carbohydrates are often attached.–Membranes are asymmetric.–Membranes are usually polarized electrically.Figure 1-7Figure 11-41) Tell the "Big Picture" story of how membranes are constructed and how they function.2) Recognize membrane lipids as amphipathic compounds that form lipid bilayers in aqueous media.Figure 11-3Page 3Membrane Function, Structure and Dynamics•Lipid Composition–Different Organisms & Cell Types–Different Organelles3) Relate the physical and chemical properties of membrane lipids to their roles in the membrane. 4) Describe the functions of membranes in cells and explain how the composition of the membrane and the physical and chemical properties of membrane components relate to those functions.Figure 11-2Figure 11-6Page 4Membrane Function, Structure and Dynamics•Lipid Composition–Inner and Outer Leaflets–Asymmetry•Fluid Mosaic Model•Components•Movement•Lipids can mover laterally with almost no energy input•Transversally is high in energy and not common unless with enzyme•Asymmetry5) Identify the location, orientation and structures of typical lipids and proteins in the asymmetric lipid bilayer.6) Describe the fluid mosaic model of membranes. Figure 11-3Figure 11-5•Can split outer layer into two leaflets•Outer and innerPage 5Membrane Function, Structure and Dynamics–Membrane Proteins•Peripheral–Sit on surface of membrane. Interact with head groups or something.–Use mild changes i.e. pH of salt change to remove•Integral–Defined»Have to use harsh treatments to remove protein–Asymmetry–Lipid-Protein InteractionsFigure 11-7Figure 11-11Figure 11-137) Define integral, peripheral, and lipid-anchored membrane proteins and recognize each type in terms of its physical and chemical characteristics.Page 6Membrane Function, Structure and Dynamics–Transmembrane -helical Proteins»hydropathy plots–-barrel Proteins»20 or more transmembrane segments form beta-sheets that line a cylinder.»Alternating amino acid are hydrophobic/hydrophilic: face bilayer/ line the cylinder.Figure 11-14Figure 11-10 & 12Figure 11-8 & 128) Interpret hydropathy plots and relate these to the physical and chemical characteristics of membrane proteins.Page 7Membrane Function, Structure and Dynamics•Fluid Mosaic Model•Amphitropic Proteins•Sometimes associated with membrane, sometimes it is not•Lipid-Linked Proteins–Defined–Functions–Types»Fatty acid linkages»Isoprenoid linkages»GPI linked (glycosylated derivatives of phosphatidylinositol)–AsymmetryFigure 11-7Figure 11-15Page 8Membrane Function, Structure and Dynamics•Fluid Mosaic Model–Membrane Dynamics•Gel vs. Fluid State–Temperature–Lipid Composition•Regulation of Membrane FluidityFigure 11-169) Define membrane fluidity and explain how fluidity is governed by fatty acid composition and cholesterol content, relate this to the physical and chemical properties of these molecules, and predict how changes in membrane composition will