MCB 450 1st Edition Lecture 9 Outline of Last Lecture I Fatty acids structure nomenclature properties II Lipids components structure properties III Functions of lipids a energy storage b components of cell membranes IV Membrane lipids a phospholipids phosphoglycerides sphingolipids b cholesterol V Lipid bilayers a why they form b bilayer fluidity lipid mobility and asymmetry Outline of Current Lecture I Membrane Proteins a peripheral b integral c lipid anchored II Membrane Transport Current Lecture Association of proteins with membranes Three types of membrane proteins integral peripheral lipid linked If you have to use a detergent to remove the protein from the membrane then it is likely that the protein spans the membrane is an integral protein A particular class of amino acids may be enriched on one side of an alpha helix The way the helix is put together can create almost a split down the middle in terms of creating a polar side and a non polar side Transmembrane segments can be predicted hydropathy plots Computational biology comes in Slide 9 12 Scoring matrix to reflect how polar or non polar a helix is Examples of hydropathy plots Graph colored coated to match alpha helices TM transmembrane domain Beta barrel membrane proteins Because of the beta sheet arrangement it is not as easy to find these doing the hydropathy analysis These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Solubilization of integral membrane proteins principle Detergent also spontaneously form micelles Bottom left picture is a solubilized protein There is a mystery about solubilizing proteins you have to try lots of different detergents It s harder to get 3 D structures of membrane proteins Goal though is to retain the native conformation when solubilizing a protein Lipid anchored proteins Lipid anchored proteins can be grouped into two categories based on whether they link to the cytoplasmic side or to the extracytoplasmic side Palmitate linkage is reversible Myristate is a more stable linkage so can t really be removed Crystallization is an essential function to cells At least two of these linkages are very important o Without them it is embryonically lethal If extracytoplasmic interaction ex doesn t happen then the organism will die as well Lipid bilayers are highly impermeable to ions and most polar molecules There are lots of solutes that use simple diffusion Water diffuses very easily Membranes as permeability barriers The removal of the hydration shell will not happen by simple diffusion o This is where the transport proteins come in How can you tell a transport process is carrier mediated facilitated The more transporters you have the faster facilitated diffusion will occur Which is transported Indole passively Glucose facilitated diffusion Active Transport About 1 3 of the ATP that is consumed by an animal at rest is consumed by the ATPase pumps to maintain the correct gradients Na K ATPase is a P type ATPase Can think of it sort of as a timer Some channels only open in response to stimuli gated channels Some of these ion channels can be controlled by the cell in terms of being open or closed Ligand activated chemically gated