1. CHAPTER 3 THE STRUCTURE AND FUNCTION OF MACROMOLECULES

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3. Introduction Macromolecules may be composed of thousands of atoms and weigh over 100,000 daltons. may be composed of thousands of atoms and weigh over 100,000 daltons. The four major classes of macromolecules are: carbohydrates, lipids, proteins, and nucleic acids. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

4. Most macromolecules are polymers Three of the four classes of macromolecules form chainlike molecules called polymers. Polymers consist of many similar or identical building blocks linked by covalent bonds. Polymers consist of many similar or identical building blocks linked by covalent bonds. The repeated units are small molecules called monomers. Some monomers have other functions of their own. Some monomers have other functions of their own. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

5. Condensation reaction or dehydration reaction Monomers are connected by covalent bonds via a condensation reaction or dehydration reaction. Releases water. Releases water. This process requires energy and is aided by enzymes. This process requires energy and is aided by enzymes. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.2a

6. Hydrolysis The covalent bonds connecting monomers in a polymer are disassembled by hydrolysis. In hydrolysis as the covalent bond is broken a hydrogen atom and hydroxyl group from a split water molecule attaches where the covalent bond used to be. In hydrolysis as the covalent bond is broken a hydrogen atom and hydroxyl group from a split water molecule attaches where the covalent bond used to be. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.2b

7. Carbohydrates Include both sugars and polymers. Monosaccharides or simple sugars- one sugar Disaccharides, double sugars, - two monosaccharides joined by a condensation reaction. Polysaccharides are polymers of monosaccharides. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

8. Sugars as a source of fuel and carbon sources Monosaccharides Molecular Formula: CH 2 O. Molecular Formula: CH 2 O. For example, glucose has the formula C 6 H 12 O 6. For example, glucose has the formula C 6 H 12 O 6. Most names for sugars end in -ose. Most names for sugars end in -ose. Monosaccharides have a carbonyl group and multiple hydroxyl groups. If the carbonly group is at the end, the sugar is an aldose, if not, the sugars is a ketose. If the carbonly group is at the end, the sugar is an aldose, if not, the sugars is a ketose. Glucose, an aldose, and fructose, a ketose, are structural isomers. Glucose, an aldose, and fructose, a ketose, are structural isomers. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

9. Classification of monosaccharides Can have 3,5 or 6 carbons. Glucose and other six carbon sugars are hexoses. Glucose and other six carbon sugars are hexoses. Five carbon backbones are pentoses and three carbon sugars are trioses. Five carbon backbones are pentoses and three carbon sugars are trioses. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

10. Fig. 5.3

11. Functions of carbohydrates a major fuel for cellular work. a major fuel for cellular work. raw material for the synthesis of other monomers, including those of amino acids and fatty acids. raw material for the synthesis of other monomers, including those of amino acids and fatty acids. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.4

12. Two monosaccharides can join with a glycosidic linkage to form a dissaccharide via dehydration synthesis. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.5a

13. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.5 While often drawn as a linear skeleton, in aqueous solutions monosaccharides form rings.

14. Polysaccharides have storage and structural roles Polysaccharides are polymers of hundreds to thousands of monosaccharides joined by glycosidic linkages. An energy storage macromolecule that is hydrolyzed as needed. Other polysaccharides- building materials for the cell or whole organism. Glucose is the primary monomer used in polysaccharides. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

15. Starch a storage polysaccharide in plants. a storage polysaccharide in plants. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.6a

16. Plants store starch within plastids, including chloroplasts. Plants can store surplus glucose in starch and withdraw it when needed for energy or carbon. Animals that feed on plants, especially parts rich in starch, can also access this starch to support their own metabolism. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

17. Animals store carbohydrates in glycogen. Humans and other vertebrates store glycogen in the liver and muscles but only have about a one day supply. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Insert Fig. 5.6b - glycogen Fig. 5.6b

18. Structural polysaccharides form strong building materials. Cellulose is a major component of the tough wall of plant cells. Cellulose is also a polymer of glucose monomers, but using beta rings. Cellulose is also a polymer of glucose monomers, but using beta rings. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.7c

19. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.8

20. Another important structural polysaccharide Chitin Chitin in the exoskeletons of arthropods (including insects, spiders, and crustaceans). forms the structural support for the cell walls of many fungi similar to cellulose, except that it contains a nitrogen- containing appendage on each glucose. Pure chitin is leathery, but the addition of calcium carbonate hardens the chitin. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.9

21. Lipids Lipids do not have polymers. Hydrophobic. This is because their structures are dominated by nonpolar covalent bonds. This is because their structures are dominated by nonpolar covalent bonds. Lipids are highly diverse in form and function. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

22. Fats store energy Although fats are not strictly polymers, they are large molecules assembled from smaller molecules by dehydration reactions. A fat is constructed from two kinds of smaller molecules, glycerol and fatty acids. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

23. Fig. 5.10a Glycerol: a three-carbon skeleton with a hydroxyl group attached to each. Fatty acid: a carboxyl group attached to a long carbon skeleton, often 16 to 18 carbons long.

24. The many nonpolar C-H bonds in the long hydrocarbon skeleton make fats hydrophobic. In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.10b

25. The three fatty acids in a fat can be the same or different. Fatty acids may vary in length (number of carbons) and in the number and locations of double bonds. No carbon-carbon double bonds: No carbon-carbon double bonds: saturated fatty acid - a hydrogen at every possible position. saturated fatty acid - a hydrogen at every possible position. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.11a

26. One or more carbon-carbon double bonds: unsaturated fatty acid - formed by the removal of hydrogen atoms from the carbon skeleton. One or more carbon-carbon double bonds: unsaturated fatty acid - formed by the removal of hydrogen atoms from the carbon skeleton. Saturated fatty acids are straight chains, but unsaturated fatty acids have a kink wherever there is a double bond. Saturated fatty acids are straight chains, but unsaturated fatty acids have a kink wherever there is a double bond. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.11b

27. Saturated Fats Most animal fats. Most animal fats. Solid at room temperature. Solid at room temperature. A diet rich in saturated fats may contribute to cardiovascular disease (atherosclerosis) through plaque deposits. A diet rich in saturated fats may contribute to cardiovascular disease (atherosclerosis) through plaque deposits. Unsaturated fats. Plant and fish fats: oils Plant and fish fats: oils liquid are room temperature. liquid are room temperature. The kinks provided by the double bonds prevent the molecules from packing tightly together. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

28. Function of fats Energy storage. Energy storage. A gram of fat stores more than twice as much energy as a gram of a polysaccharide. Plants use starch for energy storage when mobility is not a concern but use oils when dispersal and packing is important, as in seeds. Humans and other mammals store fats as long-term energy reserves in adipose cells. Cushion vital organs. Cushion vital organs. Insulation. Insulation. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

29. Phospholipids are major components of cell membranes Two fatty acids attached to glycerol and a phosphate group. The phosphate group carries a negative charge. The phosphate group carries a negative charge. Additional smaller groups may be attached to the phosphate group. Additional smaller groups may be attached to the phosphate group. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

30. Fig. 5.12 The interaction of phospholipids with water is complex. The fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head. The fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head.

31. Steroids include cholesterol and certain hormones Steroids: lipids with a carbon skeleton of four fused carbon rings. Different steroids are created by varying functional groups attached to the rings. Different steroids are created by varying functional groups attached to the rings. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.14

32. Proteins Functions Structural support, storage, transport of other substances, intercellular signaling, movement, and defense against foreign substances. Structural support, storage, transport of other substances, intercellular signaling, movement, and defense against foreign substances. Can be enzymes in a cell and regulate metabolism by selectively accelerating chemical reactions. Can be enzymes in a cell and regulate metabolism by selectively accelerating chemical reactions. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

33. All protein polymers are constructed from the same set of 20 monomers, called amino acids. Polymers of proteins are called polypeptides. A protein consists of one or more polypeptides folded and coiled into a specific conformation. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

34. Amino Acids Four components attached to a central Carbon: a hydrogen atom a hydrogen atom a carboxyl group a carboxyl group an amino group an amino group a variable R group (or side chain). a variable R group (or side chain). Differences in R groups produce the 20 different amino acids. Differences in R groups produce the 20 different amino acids. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

35. Amino acids joined by dehydration reaction The resulting covalent bond is called a peptide bond. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.16

36. A protein’s function depends on its specific conformation A functional protein consists of one or more polypeptides that have been precisely twisted, folded, and coiled into a unique shape. It is the order of amino acids that determines what the three-dimensional conformation will be. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.17

37. A protein’s specific conformation determines its function. In almost every case, the function depends on its ability to recognize and bind to some other molecule. For example, antibodies bind to particular foreign substances that fit their binding sites. For example, antibodies bind to particular foreign substances that fit their binding sites. Enzymes recognize and bind to specific substrates, facilitating a chemical reaction. Enzymes recognize and bind to specific substrates, facilitating a chemical reaction. Neurotransmitters pass signals from one cell to another by binding to receptor sites on proteins in the membrane of the receiving cell. Neurotransmitters pass signals from one cell to another by binding to receptor sites on proteins in the membrane of the receiving cell. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

38. Primary structure unique sequence of amino acids. unique sequence of amino acids. The precise primary structure of a protein is determined by inherited genetic information. The precise primary structure of a protein is determined by inherited genetic information. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.18

39. Secondary structure results from hydrogen bonds at regular intervals along the polypeptide backbone. results from hydrogen bonds at regular intervals along the polypeptide backbone. Typical shapes that develop from secondary structure are coils (an alpha helix) or folds (beta pleated sheets). Typical shapes that develop from secondary structure are coils (an alpha helix) or folds (beta pleated sheets). Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.20

40. The structural properties of silk are due to beta pleated sheets. The presence of so many hydrogen bonds makes each silk fiber stronger than steel. The presence of so many hydrogen bonds makes each silk fiber stronger than steel. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.21

41. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Tertiary structure determined by a variety of interactions among R groups and between R groups and the polypeptide backbone. determined by a variety of interactions among R groups and between R groups and the polypeptide backbone. Fig. 5.22

42. Quarternary structure aggregation of two or more polypeptide subunits. aggregation of two or more polypeptide subunits. Collagen is a fibrous protein of three polypeptides that are supercoiled like a rope. Collagen is a fibrous protein of three polypeptides that are supercoiled like a rope. This provides the structural strength for their role in connective tissue. Hemoglobin is a globular protein with two copies of two kinds of polypeptides. Hemoglobin is a globular protein with two copies of two kinds of polypeptides. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.23

43. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.24

44. Alterations in pH, salt concentration, temperature, or other factors can unravel or denature a protein. These forces disrupt the hydrogen bonds, ionic bonds, and disulfide bridges that maintain the protein’s shape. These forces disrupt the hydrogen bonds, ionic bonds, and disulfide bridges that maintain the protein’s shape. Some proteins can return to their functional shape after denaturation, but others cannot, especially in the crowded environment of the cell. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

45. Fig. 5.25

46. Nucleic Acids The amino acid sequence of a polypeptide is programmed by a gene. A gene consists of regions of DNA, a polymer of nucleic acids. DNA (and their genes) is passed by the mechanisms of inheritance. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

47. Nucleic acids store and transmit hereditary information There are two types of nucleic acids: ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). DNA provides direction for its own replication. DNA also directs RNA synthesis and, through RNA, controls protein synthesis. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

48. Organisms inherit DNA from their parents. Each DNA molecule is very long and usually consists of hundreds to thousands of genes. Each DNA molecule is very long and usually consists of hundreds to thousands of genes. When a cell reproduces itself by dividing, its DNA is copied and passed to the next generation of cells. When a cell reproduces itself by dividing, its DNA is copied and passed to the next generation of cells. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

49. DNA doesn’t work alone Proteins are responsible for implementing the instructions contained in DNA. Proteins are responsible for implementing the instructions contained in DNA. Each gene along a DNA molecule directs the synthesis of a specific type of messenger RNA molecule (mRNA). The mRNA interacts with the protein- synthesizing machinery to direct the ordering of amino acids in a polypeptide. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

50. The flow of genetic information is from DNA -> RNA -> protein. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.28

51. A nucleic acid strand is a polymer of nucleotides Nucleic acids are polymers of monomers called nucleotides. Each nucleotide consists of three parts: a nitrogen base, a pentose sugar, and a phosphate group. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

52. Fig. 5.29

53. Replication of the DNA double helix An RNA molecule is a single polynucleotide chain. DNA molecules have two polynucleotide strands that spiral around an imaginary axis to form a double helix. The double helix was first proposed as the structure of DNA in 1953 by James Watson and Francis Crick. The double helix was first proposed as the structure of DNA in 1953 by James Watson and Francis Crick. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

54. The sugar-phosphate backbones of the two polynucleotides are on the outside of the helix. Pairs of nitrogenous bases, one from each strand, connect the polynucleotide chains with hydrogen bonds. Most DNA molecules have thousands to millions of base pairs. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.30