BS 161 1st Edition Lecture 8 Outline of Last Lecture I The uses and structure of carbohydrates Outline of Current Lecture II Finish up carbohydrates III Introduction to lipids membranes Current Lecture Two common disaccharides Glucose glucose maltose Glucose fructose sucrose Common polysaccharides Starch alpha 1 4 linkages straight chain Cellulose beta 1 4 linkages straight chain Higher order cellulose structures form in plant tissue make it stronger Chitin insect exoskeleton Peptidoglycan in bacterial cell wall Unrelated hydrophobic molecules have different structures Fats storage molecules Fatty acids Cholesterol and steroids Major functions of lipids Make up a large part of cell membrane Store large amounts of energy Steroids are used as hormones Fats triglycerides made from glycerol and three fatty acids which can vary in C length and presence of double bonds Composition of fatty acid chains determines the melting temperature Tm Saturated fats without C C have higher Tm Unsaturated fats with C C have lower Tm Phospholipids glycerol bonds to two fatty acids plus a modified phosphate group the head is hydrophilic the tail is hydrophobic Phospholipids are amphipathic molecules have both hydrophilic and hydrophobic parts they can self assemble create a higher order structure without extra information
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