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chapter 4

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Gillian Goward

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Type of Structure Function Significance/ lipid examples structure Fats = fatty  Fats a.ka. Triacylglycerol  Store energy acid + o composed of 3 fatty acids and a three - carbon molecule called  Are hydrophobic glycerol, glycerol linked by ester  How do fats form? linkage o Dehydration reaction between a hydroxyl group of glycerol and carboxyl group of a fatty acid o Glycerol and fatty acid are linked by ester linkage Steroids =  4 ringed structure + side groups  Estrogen and other molecules regulates e.g. four ringed o Side groups distinguishes it from other steroids sexual development and activity in humans cholesterol,  Cholesterol is used in mammals as a starting estrogen, point for synthesis of hormones progestrone  Are amphiphatic as has both a polar and a and non polar region testosterone  Cholesterol = important component in plasma membrane Phospholipi  Composed of a glycerol that is linked to a phosphate group and to either 2  Are amphipathic as has both a polar and a  e.g. Archaea: ds = chains of fatty acids or isoprene. non polar region which is why they are phospholipids glycerol + present in plasma membrane with isoprene phosphate  Form bilayers in water  Bacteria and group + 2  NON POLAR = hyrdophobic tails Eukarya: fatty acids  POLAR = hydrophillic heards phospholipids or isoprene  Because of their amphipathic property, with fatty phospholipids do not dissolve in water, acids rather form of the 2 structures:  Bilayer is o MICELLES: lipids with short tails form dynamic and micelles not static o  LIPID BILAYERS: lipids with longer tails form bilayers  These are formed with hydrophillic heads face water, forcing hydrophobic tails together, towards inside.  These structures are highly organized and stable compared to just individual phospholipids in solution.  The reason individual amphipathic molecules are unstable in water because hydrocarbons disrupt hydrogen bonding between water molecules These structures form spontaneously and  require no input of energy LIPIDS Structure Function Significance  Fats are hyrdophobic becyase Phospholipids, glycolipids and Membranes structures and they have a significant some steroids (cholesterol) functions hydrocarbon component o Because electrons are Other steroids Hormones and regulators equally shared in C-H bond which is why they Triglycerides Food storage are hydrophobic  Lipids are defined by their Waxes Bee hives and plant leaf surfaces for the protection against water loss solubility rather than their structures. There are three important structures of lipids Act as pigments that capture or respond to sunlight found in cell:  Act as vitamins in cellular processes.  Most important function: role in plasma membrane o Fats o Steroids o phospholipids MEMBRANES Key points Structure (current and past models) Function Significance  Only lipids  Composed of lipid bilayer on  Acts as a barrier/ boundary Membranes are important that are the outside that are separating a living cell's because they allow for amphipathic selectively permeable to internal environment from its compartmentalization, are certain substances external nonliving environment which allows for efficient membrane -  DAVSON - DANIELLI  Acts as a selective barrier communication and forming "SANDWICH MODEL" (past allowing only certain molecules activity. lipids & unaccepted) to pass through; thus Compartments: o Cell membranes are controlling the flow of  May contain different constructed like a substances going in and out of enzymes sandwich the membrane 
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