Chapter 5 The Structure and Function of Large Biological Molecules PowerPoint Lecture Presentations for Biology Eighth Edition p and Jane Reece Neil Campbell Lectures by Chris Romero updated by Erin Barley with contributions from Joan Sharp Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Overview The Molecules of Life All living things are made up of four classes of large biological molecules carbohydrates carbohydrates lipids proteins and nucleic acids Within cells 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 Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Fig 5 1 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 ll d monomers Three of the four classes of life s organic g molecules are polymers Carbohydrates Proteins Nucleic acids Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings 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 th dehydration the d h d ti process Polymers are disassembled to monomers by hydrolysis a reaction that is essentially the reverse of the dehydration y reaction Animation Polymers Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Fig 5 2 HO 1 2 3 H HO Unlinked monomer Short polymer Dehydration removes a water molecule forming a new bond HO 2 1 H 3 H2O 4 H Longer polymer a Dehydration reaction in the synthesis of a polymer HO 1 2 3 4 Hydrolysis adds a water molecule breaking a bond molecule HO 1 2 3 b Hydrolysis of a polymer H H H2O HO H Fig 5 2a HO 1 2 3 H Short p polymer y HO Unlinked monomer Dehydration removes a water molecule forming a new bond molecule HO 1 2 H 3 H2O 4 H Longer polymer Dehydration a D h d ti reaction ti in i the th synthesis th i off a polymer l Fig 5 2b HO 1 2 3 4 Hydrolysis adds a water molecule breaking a bond HO 1 2 3 b Hydrolysis of a polymer H H H2O HO H The Diversity of Polymers Each cell has thousands of different kinds of macromolecules 2 3 H HO 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 Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings 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 Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Sugars Monosaccharides have molecular formulas that are usually multiples of CH2O Glucose C6H12O6 is the most common monosaccharide Monosaccharides are classified by The location of the carbonyl group as aldose or ketose The number of carbons in the carbon skeleton Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Fig 5 3 Trioses C3H6O3 Pentoses C5H10O5 Hexoses C6H12O6 Glyceraldehyde Ribose Glucose Galactose Dihydroxyacetone Ribulose Fructose Fig 5 3a Trioses C3H6O3 Pentoses C5H10O5 Hexoses C6H12O6 Glyceraldehyde Ribose Glucose Galactose Fig 5 3b Trioses C3H6O3 Pentoses C5H10O5 Hexoses C6H12O6 Dihydroxyacetone Ribulose Fructose Though often drawn as linear skeletons in aqueous solutions many sugars form rings Monosaccharides serve as a major fuel for cells and as raw material for building molecules Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Fig 5 4 a Linear and ring forms b Abbreviated ring structure Fig 5 4a a Linear and ring forms Fig 5 4b b Abbreviated ring structure A disaccharide is formed when a dehydration reaction joins two monosaccharides This covalent bond is called a glycosidic linkage Animation Disaccharides Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Fig 5 5 1 4 glycosidic linkage Glucose Glucose Maltose a Dehydration reaction in the synthesis of maltose 1 2 glycosidic li k linkage Glucose Fructose b Dehydration reaction in the synthesis of sucrose Sucrose 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 Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Storage Polysaccharides Starch a storage polysaccharide of plants consists entirely of glucose monomers Plants store surplus starch as granules within chloroplasts and other plastids Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Fig 5 6 Chloroplast Mitochondria Glycogen granules Starch 0 5 m 0 5 1 m Glycogen y g Amylose y Amylopectin a Starch a plant polysaccharide b Glycogen an animal polysaccharide Glycogen is a storage polysaccharide in animals Humans and other vertebrates store glycogen mainly in liver and muscle cells Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings 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 and beta Animation Polysaccharides Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Fig 5 7 a and glucose ring structures Glucose b Starch 1 4 linkage of glucose monomers Glucose b Cellulose 1 4 linkage of glucose monomers Fig 5 7a Glucose a and glucose ring structures Glucose Fig 5 7bc b Starch 1 4 linkage of glucose monomers c Cellulose 1 4 linkage of glucose monomers Polymers with glucose are helical Polymers with glucose are straight In straight structures structures H atoms on one strand can bond with OH groups on other strands Parallel cellulose molecules held together this way are grouped into microfibrils which form strong building materials for plants Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Fig 5 8 Cell walls Cellulose
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