BIOL 3510 1st Edition Lecture 9 Outline of Last Lecture I DNA Technology II DNA Cloning III Polymerase Chain Reactions IV Dideoxy DNA Sequencing Outline of Current Lecture I Types of Lipids II Determinants of Membrane Fluidity III Maintenance of Membrane Fluidity Current Lecture Cell membranes are selective barriers that are made of lipids and proteins Lipids are a class of molecules that are insoluble in water Examples include fatty acids triacylglycerols steroids and phospholipids Lipids are often amphipathic have both hydrophobic and hydrophilic regions Fatty acids have two chemically distinct regions the carboxylic acid and hydrocarbon chain Oils and fats triacylglycerols store energy and are formed by dehydration synthesis The basic steroid skeleton is 4 linked carbon rings Phospholipids are the most common type of cell membrane lipid Phosphatidylcholine is the most common phospholipid Phospholipids form bilayers and assemble into self sealing containers Phospholipids move within one face of a bilayer but do not flip flop spontaneously Determinants of membrane fluidity 1 Temperature 2 Phospholipid characteristics hydrocarbon tail length shorter tails are less interactive more fluid number of double bonds in the tail saturated tails are less fluid unsaturated tails are more fluid Maintenance of membrane fluidity 1 Yeast and bacteria alter tail length and saturation in response to temperature changes 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 2 Animals cholesterol stiffens the membrane Lipds are created on the cytosolic surface of the ER scramblase and flippases are enzymes that transfer phospholipids from one membrane face to another The cytosolic face of a membrane is constant during transport Lipid bi layers are asymmetric Membrane proteins interact with membranes in different ways
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