UW-Madison BIOLOGY 151 - Membrane Fluidity (3 pages)

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Membrane Fluidity

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Membrane Fluidity


Lecture notes

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Lecture Note
University of Wisconsin, Madison
Biology 151 - Introductory Biology

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Bio 151 1nd Edition Lecture 4 Outline of Last Lecture Nucleic acids The cell theory Biological Membranes Structure o Major components 95 Phospholipids proteins Models of organization o Minor components 5 Glycoproteins and glycolipids cell identify markers Sterols fluidity buffers Outline of Current Lecture Membrane Fluidity Membrane Transport o Transport proteins o Energy Requirements Passive and Active Transport o Coupling mechanisms Current Lecture 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 Membrane Fluidity depends on lipid structure o Phospholipids aren t bonded can move all over No restriction on movement As fluid as salad dressing Membranes have to be this fluid in order to work o Living organisms need to change lipids to maintain fluidity as temperature changes Strategies organisms use to increase fluidity when temperature decreases o Increase degree of unsaturation in lipids Increase number of unsaturated double bonds in fatty acids Increase number of fatty acids with unsaturated bonds as temperature drops less packed with phospholipids less dense but maintained fluidity kinked o Increase cholesterol content of membrane cholesterol is a fluid buffer Cholesterol is bulky hydrophobic mostly unipolar acts like the kinky unsaturated lipid makes it more fluid at low temperatures Motion of lipids will speed up at high temperature lipids move way too fast but cholesterol will calm the lipds down to prevent too much disorganization With cholesterol higher fluidity at low temps lower fluidity at high temps Fluidity of membrane allows uncharged time organisms to go into the cell Permeability of Phospholipid Bilayer o Small uncharged molecule will move freely O2 CO2 NO H2O usually o Small hydrophobic fat soluble molecules ei Vitamins Transport proteins handle traffic across membrane cells make lots of these makes two types 1 from in to out 2 from out to in o

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