CH5 - CH5 Macromolecules The Molecules of Life All living...

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1 CH5 – Macromolecules The Molecules of Life • All living things are made up of four classes of large biological molecules: carbohydrates, lipids, proteins, and nucleic acids Macromolecules are large molecules composed of thousands of covalently connected atoms • Molecular structure and function are inseparable Macromolecules are polymers, built from monomers • A polymer is a long molecule made of repeating, similar, building blocks • building-block molecules are called monomers • Three of the four classes of macromolecules are polymers: Carbohydrates Proteins Nucleic acids • A condensation reaction ( more specifically a dehydration reaction) occurs when two monomers bond together Enzymes are macromolecules that speed up the dehydration process A hydrolysis reaction is essentially the reverse of the dehydration reaction The Synthesis and Breakdown of Polymers
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2 CARBOHYDRATES Carbohydrates include sugars and the polymers of sugars • The simplest carbohydrates are monosaccharides, or single sugars 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 • Monosaccharides are classified (named) by The location of the carbonyl group (as aldose or ketose) The number of carbons in the carbon skeleton Fig. 5-3a Aldoses Glyceraldehyde Ribose Glucose Galactose Hexoses (C 6 H 12 O 6 ) Pentoses (C 5 H 10 O 5 ) Trioses (C 3 H 6 O 3 )
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3 Fig. 5-3b Ketoses Dihydroxyacetone Ribulose Fructose Hexoses (C 6 H 12 O 6 ) Pentoses (C 5 H 10 O 5 ) Trioses (C 3 H 6 O 3 ) Fig. 5-4a (a) Linear and ring forms Though often drawn as linear skeletons, in aqueous solutions many sugars form rings • A disaccharide is formed when a dehydration reaction joins two monosaccharides • This covalent bond is called a glycosidic linkage
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4 Fig. 5-5 (b) Dehydration reaction in the synthesis of sucrose Glucose Fructose Sucrose Maltose Glucose Glucose (a) Dehydration reaction in the synthesis of maltose 1–4 glycosidic linkage 1–2 glycosidic linkage Polysaccharides have storage and structural roles STORAGE Starch , a storage polysaccharide of plants, consists entirely of glucose monomers Glycogen is a storage polysaccharide in animals Humans and other vertebrates store glycogen mainly in liver and muscle cells Polysaccharides have storage and structural roles STRUCTURAL 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 )
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5 Fig. 5-7a (a) α and β glucose ring structures α Glucose β Glucose Fig. 5-7bc (b) Starch: 1–4 linkage of α glucose monomers (c) Cellulose: 1–4 linkage of β glucose monomers • Enzymes that digest starch by hydrolyzing α linkages can’t hydrolyze β linkages in cellulose • Cellulose in human food passes through the
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CH5 - CH5 Macromolecules The Molecules of Life All living...

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