Lecture 2 Outline - Chapter 5 The Molecules of Life All...

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Chapter 5: The Molecules of Life All living things are made up of four classes of large biological molecules: carbohydrates, lipids, proteins, and nucleic acids Within cells, small organic molecules are joined together to form larger molecules Macromolecules are large molecules composed of thousands of covalently connected atoms Molecular structure and function are inseparable Concept 5.1: Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small building-block molecules are called monomers Three of the four classes of life’s organic molecules are polymers: Carbohydrates Proteins Nucleic acids The Synthesis and Breakdown of Polymers A condensation reaction or more specifically a dehydration reaction occurs when two monomers bond together through the loss of a water molecule Enzymes are macromolecules that speed up the dehydration process Polymers are disassembled to monomers by hydrolysis , a reaction that is essentially the reverse of the dehydration reaction Figure 5.2 The synthesis and breakdown of polymers Concept 5.2: Carbohydrates serve as fuel and building material Carbohydrates include sugars and the polymers of sugars The simplest carbohydrates are monosaccharides, or single sugars Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks Sugars Monosaccharides have molecular formulas that are usually multiples of CH 2 O Glucose (C 6 H 12 O 6 ) is the most common monosaccharide
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Monosaccharides are classified by The location of the carbonyl group (as aldose or ketose) The number of carbons in the carbon skeleton Figure 5.3 The structure and classification of some monosaccharides Figure 5.4 Linear and ring forms of glucose A disaccharide is formed when a dehydration reaction joins two monosaccharides This covalent bond is called a glycosidic linkage Figure 5.5 Examples of disaccharide synthesis Polysaccharides Polysaccharides , the polymers of sugars, have storage and structural roles The structure and function of a polysaccharide are determined by its sugar monomers and the positions of glycosidic linkages Storage Polysaccharides Starch , a storage polysaccharide of plants, consists entirely of glucose monomers Plants store surplus starch as granules within chloroplasts and other plastids Figure 5.6 Storage polysaccharides of plants and animals Glycogen is a storage polysaccharide in animals Humans and other vertebrates store glycogen mainly in liver and muscle cells Structural Polysaccharides The polysaccharide cellulose is a major component of the tough wall of plant cells Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ The difference is based on two ring forms for glucose: alpha ( α ) and beta ( β ) Figure 5.7 Starch and cellulose structures Polymers with α glucose are helical
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