MCB 450 1st Edition Lecture 9Outline of Last Lecture I. Fatty acids: structure, nomenclature, propertiesII. Lipids: components, structure, propertiesIII. Functions of lipids:a. energy storageb. components of cell membranesIV. Membrane lipidsa. phospholipids: phosphoglycerides & sphingolipidsb. cholesterolV. Lipid bilayersa. why they formb. bilayer fluidity lipid mobility and asymmetryOutline of Current Lecture I. Membrane Proteinsa. peripheralb. integralc. lipid-anchoredII. Membrane TransportCurrent LectureAssociation 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 theprotein spans the membrane -- is an integral proteinA 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 apolar side and a non-polar sideTransmembrane 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 domainBeta-barrel membrane proteins-Because of the beta sheet arrangement it is not as easy to find these doing the hydropathy analysisThese 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 detergentsIt's harder to get 3-D structures of membrane proteins-Goal though is to retain the native conformation when solubilizing a proteinLipid-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 importantoWithout them it is embryonically lethal-If extracytoplasmic interaction (ex) doesn't happen then the organism will die as wellLipid bilayers are highly impermeable to ions and most polar molecules-There are lots of solutes that use simple diffusion-Water diffuses very easilyMembranes as permeability barriers-The removal of the hydration shell will not happen by simple diffusionoThis 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 occurWhich is transported...-Indole -- passively-Glucose -- facilitated diffusionActive Transport-About 1/3 of the ATP that is consumed by an animal at rest is consumed by the ATPase pumps tomaintain the correct gradientsNa-K ATPase is a P-type ATPase-Can think of it sort of as a timerSome 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