Chapter 3 - Chapter 3 Macromolecules What Kinds of...

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Chapter 3 Macromolecules What Kinds of Molecules Characterize Living Things? • Four major types of molecules are characteristic of living things: proteins, carbohydrates, lipids, and nucleic acids. • Most of these biological molecules are polymers. • Polymers are formed by covalent linkages of smaller units called monomers; • Molecules with molecular weights greater than 1,000 daltons (atomic mass units) are usually classified as macromolecules. Functional groups give specific properties to molecules • Each functional group has a specific chemical property and consistent behavior, which it confers to the larger molecule. Isomers have different arrangements of the same atoms • Isomers are molecules that have the same chemical formula, but the atoms are arranged differently. • Structural isomers differ in how their atoms are joined together. • Optical isomers occur when a carbon atom has four different atoms or groups of atoms attached to it and are mirror images Most macromolecules are formed by dehydration synthesis (condensation) and broken down by hydrolysis • Macromolecules are made from smaller monomers by means of dehydration synthesis (loss of water). • Dehydration synthesis results in covalently bonded monomers, releasing a molecule of water for each covalent bond formed. • Energy must be added to make or break a polymer. • The reverse reaction, in which polymers are broken back into monomers, is a called a hydrolysis reaction ( hydro means water; lysis , break). • In a hydrolysis reaction, water reacts with the covalent bonds that link the polymer together. Special proteins, called enzymes, are needed to make polymers from monomers. What Are the Chemical Structures and Functions of Proteins? • Proteins are molecules with diverse structures and functions. • Proteins have important roles in: • Structural support • Protection • Catalysis • Transport • Defense • Regulation • Movement • Poteins are made from 20 amino acids. • Proteins range in size from a few amino acids to thousands of them. • Some proteins are composed of a single chain of amino acids, called a polypeptide. • Other proteins have more than one polypeptide chain. • Folding is crucial to the function of a protein and is influenced largely by the sequence of amino acids. • Each different type of protein has a characteristic amino acid composition and order.
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Amino acids are the building blocks of proteins • Amino acids have carboxyl and amino groups—they function as both acid and base . + ). • The amino group is the nitrogen-containing part (H 3 N). The acid is a carboxyl group (COO ). • At the pH level of most cells, both the amino and the carboxyl group are ionized, the carboxyl group has lost a hydrogen ion, and the amino group has gained one. • Due to the presence of the amino and carboxyl group, amino acids are simultaneously acids
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This note was uploaded on 12/03/2010 for the course BSC 2010 taught by Professor Bowes during the Spring '08 term at University of Florida.

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Chapter 3 - Chapter 3 Macromolecules What Kinds of...

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