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Chapter 11. Biological Membranes: Part 1. Membranes. Part 1 and 2 Learning Goals: To Know. The function of biological membranes The structure and composition membranes and their molecules Dynamics of membranes Structure and function of membrane proteins
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Chapter 11 Biological Membranes: Part 1
Membranes Part 1 and 2 Learning Goals: To Know • The function of biological membranes • The structure and composition membranes and their molecules • Dynamics of membranes • Structure and function of membrane proteins • Transport across biological membranes
Why are TEMs of membranes always light in the middle and dark on the sides? 50 – 80 Å Thick EOC Problem 5 has to do with the length of a fatty acid: how does this play into the thickness of this membrane?
Cells Are Loaded with Membranes What’s the answer to the previous thought question?
Lipids aggregate into structures in water • Structures formed depend on: • type of lipid • concentration • Micelles • Liposomes • Bilayers
Lipids in Water EOC Problem 3 … Number of SDS moleucles/micelle. You will need to calculate the MW of dodecyl-sulfate.
Functions of Proteins in Membranes • Receptors: detecting signals from outside • Light (opsin) • Hormones (insulin receptor) • Neurotransmitters (acetylcholine receptor) • Pheromones (taste and smell receptors) • Channels, gates, pumps • Nutrients (maltoporin) • Ions (K-channel) • Neurotransmitters (serotonin reuptake protein) • Enzymes • Lipid biosynthesis (some acyltransferases) • ATP synthesis (F0F1 ATPase/ATP synthase)
Glycophorin – Transmembrane Protein Tetra-Saccharides, N-linked Tetra-Saccharides, O-linked
Bacteriochlorophyll – Reaction Center Chlorophylls in Red
Great Illustration of Phospholipid as a Fluid Sec A (chaperone) in blue ribbon. Cytoplasmic side with ATP (bright light) Sec YE in Cream Space-filling cut away to show channel Transported protein in red thread
Another Great Illustration of Phospholipid as a Fluid G Protein – major signaling protein, next Chapter.
Phospholipid Associated with Isolated Membrane Proteins Sheep Aquaporin Fo Portion of V type Na-ATPase
Remember Hydropathic Index? Non Polar R groups have Positive Hydropathic Indices Y and W are negative
Hydropathy Index Calculated from a Moving -Window of 7 to 20 Amino Acids
Transmembrane Proteins – Positions of Y and W. Polar R – groups are Blue Y is Orange W is Red
Another Great Illustration showing the Membrane as a Fluid Surface of a B-cell showing the B-cell Receptor (purple, mono-valentIgM) binding to an HIV particle.
Membranes can transition from Gels to Fluids a. Gel State b. Liquid Ordered Liquid Disordered
Membrane Lipid Movement over 56 msec EOC Problem 6 involves temperature effects on lateral diffusion in membranes.
Some Membrane Proteins Have Cytoskeleton Restricted Movement
Rafts and GPI-linked Proteins Rafts and Sea
Hierarchy of raft-based heterogeneity in cell membranes D Lingwood, K Simons Science 2010;327:46-50 Published by AAAS
Integral Membrane Proteins Involved in Cell-Cell Communication
Membrane Fusion Events,An Overview To do this, proteins have to get two membranes very close together so they touch.
Things to Know and Do Before Class The major and minor membrane phospholipids. Transmembrane protein structures and how they are held into the membrane. Peripheral membrane proteins and how they are attached to the membrane. Membrane temperature driven transitions. What AFM tells us about membrane structure. Membrane fusions + formation of endosomes. EOC Problems: 3, 5, 6 (Hint need to calc SDS mole wt 288 Daltons)