MacromoleculesCh5 - Campbell and Reece Chapter 5 Page 1 The...

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Campbell and Reece Chapter 5 Page 1 The Structure and Function of Large Biological Molecules I. Important Classes of Large Biological Molecules polysaccharides (a subset of carbohydrates) lipids proteins nucleic acids Polymers a large molecule consisting of many identical or similar smaller molecules (monomers) linked by bonds – analogous to a string of pearls or beads protein, nucleic acids and polysaccharides are polymers; lipids are not polymers a small number of monomers (i.e., 40 to 50 common monomers) can be ordered into a large number of unique macromolecules Although the polymeric macromolecules differ in their monomeric subunits, the chemical mechanisms used to make and break polymers are the same condensation reactions (dehydration reactions) are used to make the different classes of macromolecules (two monomers become covalently bonded to each other and this results in the loss of a water molecule). Figure 5.2 - one monomer contributes -OH and the other provides the H Macromolecules are degraded by the reverse reaction (hydrolysis - to break with water - "water" "break") - Refer to Lysosomes in Chapter 6 II. Carbohydrates Sugars and their polymers Fuel and building material 1. Monosaccharides (Fig 5.3) Simple - single sugars Molecular formula CH 2 O (e.g. glucose C 6 H 12 O 6 ) Monosaccharides are used as nutrients for the generation of cellular energy carbon skeletons for the synthesis of other small organic molecules incorporation into structural or storage polymers Monosaccharides vary in a number of ways including i) The location of carbonyl group aldehyde - aldose sugar - glucose ketone - ketose sugar - fructose ii) The length of carbon chain 3 to 7 carbon sugars iii) The groups attached to asymmetric carbons The linear structure of sugars is used often to represent them, however in aqueous solutions most sugars form rings (Fig 5.4)
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Campbell and Reece Chapter 5 Page 2 2. Disaccharides Two monosaccharides joined by a glycosidic linkage (formed by a dehydration reaction) Figure 5.5 e.g., maltose = glucose + glucose lactose = glucose + galactose sucrose (table sugar) = glucose + fructose 3. Polysaccharides Carbohydrates that are macromolecules (few hundred to few thousand monosaccharides) Functions i) Storage Plants produce starch for storage in plastids amylose = α -1,4 linked glucose (helical polymer) amylopectin = branched molecule in which amylose chains are connected by α -1,6 glycosidic linkages Animals produce glycogen and store it in mainly liver and muscle cells - glycogen is similar to amylopectin but more extensively branched. ii) Structural
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MacromoleculesCh5 - Campbell and Reece Chapter 5 Page 1 The...

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