BIOL 3510 1st Edition Lecture 9 Outline of Last Lecture I. DNA TechnologyII. DNA CloningIII. Polymerase Chain ReactionsIV. Dideoxy DNA SequencingOutline of Current Lecture I. Types of LipidsII. Determinants of Membrane FluidityIII. Maintenance of Membrane FluidityCurrent LectureCell 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, andphospholipids. 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. Temperature2. 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 changesThese 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 membraneLipds 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
View Full Document
Unlocking...