03 Membranes - B iochemis ry E duca ion Department of...

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Unformatted text preview: B iochemis ry E duca ion Department of iochemistry & Molecular iology University of New Mexico BIOC 423 Int oducto y Biochemist y Membranes and Membrane Transport OBJECTIVES Be able to discuss the structure of biological membranes Identify the factors that alter the mobility of biological membranes Describe the differences between passive transport and active transport Identify the differences between facilitated diffusion, symporters and antiporters Be able to describe specific examples for each of the above transport systems. OUTLINE Unique structural properties of amphipathic lipids Membrane lipids Phospholipids Sphingolipids Cholesterol Micells, Monolayers, Liposomes Lipid bilayer Membrane model Asymetrical lipid distribution Membrane proteins Integral peripheral proteins Mobility Transport system nomenclature Diffusion controlled Simple diffusion (transport follows a concentration gradient) Facilitated diffusion Active transport (energy is both direct and indirect) Energy source ATP Gradient (usually created by ATP dependent transport) Photochemical Transport models Uniport Symport Antiport LECTURE CONTENT Membrane functions Throughout the remainder of this course membranes will become both a repeated problem and solution to problems. Membranes will provide barriers around cells that keep the insides of the cell in and the outside sources of fuel out. Once inside of the cell there are multiple organelles all surrounded with membranes, isolating the various compartments of the cell. In many cases movement of substrate molecules across these membranes is a method of controlling cellular metabolism and importantly preventing reactions that interfere with each other. For example breaking down and making a glucose molecule or fatty acid in the same compartment of the cell at the same time serves only to waste cellular resources. On the other hand, separating different processes in a single cell adds significant complexity in regulation and intra- and inter-cell communication as well as the transport of essential metabolites between cells and compartments within a cell. Unique structural properties of amphipathic lipids We have already discussed the structure of the lipid component of membranes. When oil and water are mixed in the same container the two fluids do not interact with each other. They separate and the oil layer floats on the top of the water layer. There is no interaction between these two types of molecules other than to avoid each other. Many of the lipids that we have discussed have two part to them. One part will interact with the oil or hydrophobic (water hating layer) while the other end of our lipid molecule will interact with the aqueous layer. This part of the molecule is called the hydrophilic portion or water loving part. The characteristic of structural lipids that make up membranes is that they contain both hydrophilic and hydrophobic ends of the molecule. The term amphipathic means interacting with both water and oil. All amphiphthic molecules can be modeled by the figure, below, that identifies the two different parts of a single molecule....
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This note was uploaded on 04/05/2008 for the course BIOCHEM 423 taught by Professor Osgood during the Spring '08 term at New Mexico.

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03 Membranes - B iochemis ry E duca ion Department of...

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