Lec3notescomplete - Bio1A Dr McCray Lec 3 Complete Notes 1...

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Bio1A Dr. McCray Lec 3 Complete Notes 1 Molecules of Life ± Within cells, small organic molecules are joined together to form larger molecules ± Macromolecules are large molecules composed of thousands of covalently connected atoms Macromolecules are polymers, built from monomers ± A polymer is a long molecule consisting of many similar building blocks called monomers ± Three of the four classes of life’s organic molecules are polymers: ± Carbohydrates ± Proteins ± Nucleic acids The Synthesis and Breakdown of Polymers ± Monomers form larger molecules by condensation reactions called dehydration reactions ± Polymers are disassembled to monomers by hydrolysis , a reaction that is essentially the reverse of the dehydration reaction Fig. 5-2 The Diversity of Polymers ± Each cell has thousands of different kinds of macromolecules ± Macromolecules vary among cells of an organism, vary more within a species, and vary even more between species ± An immense variety of polymers can be built from a small set of monomers 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 is the most common monosaccharide ± Monosaccharides are classified by location of the carbonyl group and by number of carbons in the carbon skeleton Fig. 5-3 Monosaccharides ± Monosaccharides serve as a major fuel for cells and as raw material for building molecules ± Though often drawn as a linear skeleton, in aqueous solutions they form rings ± A disaccharide is formed when a dehydration reaction joins two monosaccharides ± This covalent bond is called a glycosidic linkage Fig. 5-4, Fig. 5-5
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Bio1A Dr. McCray Lec 3 Complete Notes 2 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 ± Glycogen is a storage polysaccharide in animals ± Humans and other vertebrates store glycogen mainly in liver and muscle cells Fig. 5-6a, Fig. 5-6b Structural Polysaccharides ± 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 ) Fig. 5-7 Alpha vs. Beta Polymers ± Polymers with alpha glucose are helical ± Polymers with beta glucose are straight ± In straight structures, H atoms on one strand can bond with OH groups on other strands
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This note was uploaded on 09/16/2010 for the course BIO 1A taught by Professor Mccray during the Fall '09 term at Merritt College.

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Lec3notescomplete - Bio1A Dr McCray Lec 3 Complete Notes 1...

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