1. 24.3 Amino Acids and Their Polymers 1 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Chapter 24 The Chemistry of Life 24.1 A Basis for Life 24.2 Carbohydrates 24.3 Amino Acids and Their Polymers 24.4 Lipids 24.5 Nucleic Acids 24.6 Metabolism

2. 24.3 Amino Acids and Their Polymers 2 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Strength-building exercises can cause your muscles to become larger and stronger. This could not happen without amino acids. CHEMISTRY & YOU Why do your muscles need amino acids?

3. 24.3 Amino Acids and Their Polymers 3 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Amino Acids What is the general structure of an amino acid? Amino Acids

4. 24.3 Amino Acids and Their Polymers 4 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Many biological compounds contain nitrogen in addition to carbon, oxygen, and hydrogen. Amino Acids Some of the most important nitrogen- containing molecules in organisms are amino acids. In fact, the polymers of amino acids make up more than one-half of the dry weight of your body.

5. 24.3 Amino Acids and Their Polymers 5 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. An amino acid is any compound that contains an amino group (—NH 2 ) and a carboxyl group (—COOH) in the same molecule. For chemists and biochemists, however, the term is usually reserved for the 20 common amino acids that are formed and used by living organisms. Amino Acids

6. 24.3 Amino Acids and Their Polymers 6 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Amino acids consist of a carboxyl group, an amino group, a hydrogen, and an R- group side chain that are all covalently bonded to a central carbon atom. Amino Acids

7. 24.3 Amino Acids and Their Polymers 7 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. The chemical nature of the side-chain group accounts for the differences in properties of the 20 amino acids. In some amino acids, the side chains are nonpolar aliphatic or aromatic hydrocarbons. In other amino acids, the side chains are neutral but polar. In still others, the side chains are acidic or basic. Amino Acids

8. 24.3 Amino Acids and Their Polymers 8 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Because the central carbon of an amino acid is asymmetric, these compounds can exist as enantiomers. Enantiomers may be right- or left-handed. Nearly all the amino acids found in nature are of the left-handed, or L, form. Amino Acids

9. 24.3 Amino Acids and Their Polymers 9 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Common Amino Acids NameSymbolNameSymbol AlanineAlaLeucineLeu ArginineArgLysineLys AsparagineAsnMethionineMet Aspartic acidAspPhenylalaninePhe CysteineCysProlinePro GlutamineGlnSerineSer Glutamic acidGluThreonineThr GlycineGlyTryptophanTrp HistadineHisTyrosineTyr IsoleucineIleValineVal Interpret Data The table below gives the names of amino acids with their three-letter abbreviations.

10. 24.3 Amino Acids and Their Polymers 10 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Does the table in this lesson show all existing amino acids?

11. 24.3 Amino Acids and Their Polymers 11 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Does the table in this lesson show all existing amino acids? No, it shows the 20 common amino acids that are formed and used by living organisms. These are the amino acids that are important to chemists and biochemists.

12. 24.3 Amino Acids and Their Polymers 12 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Peptides and Proteins What determines the differences in the chemical and physiological properties of peptides and proteins? Peptides and Proteins

13. 24.3 Amino Acids and Their Polymers 13 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. A peptide is any combination of amino acids in which the amino group of one amino acid is united with the carboxyl group of another amino acid. Peptides and Proteins The amide bond between the carboxyl group of one amino acid and the nitrogen in the amino group of the next amino acid in the peptide chain is called a peptide bond.

14. 24.3 Amino Acids and Their Polymers 14 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Peptide bonds always involve the central amino acid and central carboxyl groups. The side chains are not involved in the bonding. Peptides and Proteins Amino acid Peptide

15. 24.3 Amino Acids and Their Polymers 15 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. A free amino group is at one end of the peptide. The convention is to write the peptide formula so that the free amino group is at the left end. There is also a free carboxyl group, which appears at the right end of the molecule. Amino acid Peptide Peptides and Proteins

16. 24.3 Amino Acids and Their Polymers 16 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. More amino acids may be added to the peptide in the same fashion to form long chains by condensation polymerization. The order in which the amino acids of a peptide are linked is called the amino acid sequence of that molecule. The amino acid sequence of a peptide is conveniently expressed using the three-letter abbreviations for the amino acids. Peptides and Proteins

17. 24.3 Amino Acids and Their Polymers 17 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. For example, Asp—Glu—Gly represents a peptide containing three amino acids. This tri-peptide contains aspartic acid, glutamic acid, and glycine, in that order, with the free amino group assumed to be on the left end (on the Asp) and the free carboxyl group on the right end (on the Gly). Peptides and Proteins –Note that Asp—Glu—Gly is a different peptide from Gly—Glu—Asp because the order of amino acids is reversed, and thus the free amino group and free carboxyl group are on different amino acids.

18. 24.3 Amino Acids and Their Polymers 18 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. In theory, the process of adding amino acids to a peptide chain can continue indefinitely. Peptides and Proteins A peptide with more than ten amino acids is a polypeptide. A peptide with more than 100 amino acids is a protein.

19. 24.3 Amino Acids and Their Polymers 19 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Proteins are an important class of biomolecules. For example, your skin, hair, nails, and muscles are all made of proteins. Proteins are needed for almost all chemical reactions that occur in the body. Peptides and Proteins

20. 24.3 Amino Acids and Their Polymers 20 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. We can make some of the amino acids that our cells use to make proteins. Other amino acids must be obtained by Peptides and Proteins eating foods rich in proteins. Beans and brown rice are good sources of amino acids.

21. 24.3 Amino Acids and Their Polymers 21 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Why do your muscles need amino acids? CHEMISTRY & YOU

22. 24.3 Amino Acids and Their Polymers 22 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Why do your muscles need amino acids? Your muscles need amino acids because muscles are made of proteins, which are made from amino acids. Your body produces some of these amino acids; others must be obtained from protein-rich food. CHEMISTRY & YOU

23. 24.3 Amino Acids and Their Polymers 23 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Differences in the chemical and physiological properties of peptides and proteins result from differences in the amino acid sequence. Peptides and Proteins As many as 20 100 different amino acid sequences are possible for a protein of 100 amino acids containing a combination of the 20 different amino acids.

24. 24.3 Amino Acids and Their Polymers 24 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. The figure below represents a long peptide chain of a protein. Peptides and Proteins Protein molecules are folded into relatively stable three-dimensional shapes.

25. 24.3 Amino Acids and Their Polymers 25 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. This figure shows how sections of a peptide chain may coil into a regular spiral, known as a helix. Peptides and Proteins Protein molecules are folded into relatively stable three-dimensional shapes.

26. 24.3 Amino Acids and Their Polymers 26 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Peptide chains may also be arranged side by side to form a pleated sheet, as shown below. Peptides and Proteins Protein molecules are folded into relatively stable three-dimensional shapes.

27. 24.3 Amino Acids and Their Polymers 27 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Irregular folding of the chains can also occur. Peptides and Proteins Protein molecules are folded into relatively stable three-dimensional shapes.

28. 24.3 Amino Acids and Their Polymers 28 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. The three-dimensional shape of a protein is determined by interactions among the amino acids in its peptide chains. Protein shape is maintained partly by hydrogen bonds between adjacent folded chains. Peptides and Proteins

29. 24.3 Amino Acids and Their Polymers 29 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Covalent bonds also form between sulfur atoms of cysteine side chains that are folded near each other. In that way, separate polypeptide chains may be joined into a single protein. Peptides and Proteins

30. 24.3 Amino Acids and Their Polymers 30 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. The three-dimensional structure of myoglobin, the oxygen storage protein of muscle tissue, is shown here. Peptides and Proteins The peptide chains of most of the myoglobin molecule are twisted into helixes.

31. 24.3 Amino Acids and Their Polymers 31 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Myoglobin also contains a nonprotein structure called heme. Peptides and Proteins Heme contains four linked rings with an iron(II) ion (Fe 2+ ) at the center. Molecular oxygen binds to the heme iron.

32. 24.3 Amino Acids and Their Polymers 32 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. How many amino acids are in a peptide? How many are in a polypeptide? How many are in a protein?

33. 24.3 Amino Acids and Their Polymers 33 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. How many amino acids are in a peptide? How many are in a polypeptide? How many are in a protein? A peptide contains 2 or more amino acids joined together by a peptide bond. A polypeptide contains 10 or more amino acids. A protein contains about 100 or more peptides.

34. 24.3 Amino Acids and Their Polymers 34 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Enzymes How do enzymes affect the rates of reactions in living things? Enzymes

35. 24.3 Amino Acids and Their Polymers 35 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Enzymes How do enzymes affect the rates of reactions in living things? Enzymes are proteins that act as biological catalysts. Enzymes

36. 24.3 Amino Acids and Their Polymers 36 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Enzymes increase the rates of chemical reactions in living things. Enzymes

37. 24.3 Amino Acids and Their Polymers 37 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. In 1926, the American chemist James B. Sumner reported the first isolation and crystallization of an enzyme. The enzyme he isolated was urease. Urease hydrolyzes urea, a constituent of urine, into ammonia and carbon dioxide. urease H 2 N–C–NH 2 (aq) + H 2 O(l) 2NH 3 (g) + CO 2 (g) O UreaWaterAmmoniaCarbon dioxide Enzymes

38. 24.3 Amino Acids and Their Polymers 38 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Since the discovery of urease, thousands of enzymes have been isolated and structurally characterized as proteins. Enzymes

39. 24.3 Amino Acids and Their Polymers 39 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. In addition to being able to promote reactions, enzymes have two other properties of true catalysts. Enzymes

40. 24.3 Amino Acids and Their Polymers 40 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. In addition to being able to promote reactions, enzymes have two other properties of true catalysts. First, they are unchanged by the reaction they catalyze. Enzymes

41. 24.3 Amino Acids and Their Polymers 41 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. In addition to being able to promote reactions, enzymes have two other properties of true catalysts. First, they are unchanged by the reaction they catalyze. Second, they do not change the normal equilibrium position of a chemical system. Enzymes –The same amount of product is eventually formed whether or not an enzyme is present.

42. 24.3 Amino Acids and Their Polymers 42 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Few reactions in cells ever reach equilibrium, however. The products tend to convert rapidly to another substance in a subsequent enzyme- catalyzed reaction. –According to Le Châtelier’s principle, such removal of a product pulls the reaction toward completion. Enzymes

43. 24.3 Amino Acids and Their Polymers 43 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Enzymes catalyze most of the chemical changes that occur in the cell. How Enzymes Work Enzymes Substrates are the molecules on which an enzyme acts.

44. 24.3 Amino Acids and Their Polymers 44 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. In a typical enzymatic reaction, the substrate interacts with side chains of the amino acids on the enzyme. How Enzymes Work Enzymes

45. 24.3 Amino Acids and Their Polymers 45 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. A substrate molecule must make contact with, and bind to, an enzyme molecule before the substrate can be transformed into the product. How Enzymes Work Enzymes

46. 24.3 Amino Acids and Their Polymers 46 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. The place on an enzyme where a substrate binds is called the active site. How Enzymes Work Enzymes An active site is usually a pocket or crevice formed by folds in the peptide chains of the enzyme protein.

47. 24.3 Amino Acids and Their Polymers 47 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. The peptide chain of an enzyme is folded in a unique way to accommodate the substrate at the active site. How Enzymes Work Enzymes

48. 24.3 Amino Acids and Their Polymers 48 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Since the active site of each enzyme has a distinctive shape, only a specific substrate molecule can fit into the enzyme, similar to how only one key shape will fit into a certain lock. How Enzymes Work Enzymes Thus, each enzyme can catalyze only one chemical reaction at a time.

49. 24.3 Amino Acids and Their Polymers 49 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. An enzyme-substrate complex is formed when an enzyme molecule and a substrate molecule are joined. How Enzymes Work Enzymes

50. 24.3 Amino Acids and Their Polymers 50 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Carbonic anhydrase catalyzes the reversible breakdown of carbonic acid to carbon dioxide and water. How Enzymes Work Enzymes H 2 CO 3 (aq) CO 2 (g) + H 2 O(l) carbonic anhydrase Carbonic acidCarbon dioxide Water One molecule of carbonic anhydrase can catalyze the breakdown of 36 million molecules of carbonic acid in one minute!

51. 24.3 Amino Acids and Their Polymers 51 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. The figure below shows a model of the enzyme-substrate complex formed between carbonic anhydrase and its substrate, carbonic acid. How Enzymes Work Enzymes

52. 24.3 Amino Acids and Their Polymers 52 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Some enzymes can directly catalyze the transformation of biological substrates without assistance from other substances. Other enzymes need nonprotein coenzymes, also called cofactors, to assist the transformation. Coenzymes Enzymes

53. 24.3 Amino Acids and Their Polymers 53 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Coenzymes are metal ions or small organic molecules that must be present for an enzyme-catalyzed reaction to occur. Coenzymes Enzymes Many water-soluble vitamins, such as B vitamins, are coenzymes. Metal ions that act as coenzymes include the cations of magnesium, potassium, iron, and zinc.

54. 24.3 Amino Acids and Their Polymers 54 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Liver contains high levels of catalase. Enzymes When a small amount of crushed liver cells is added to a solution of hydrogen peroxide, oxygen gas is rapidly evolved. Coenzymes

55. 24.3 Amino Acids and Their Polymers 55 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. The enzyme catalase includes an iron(III) ion in its structure. Enzymes Catalase catalyzes the breakdown of hydrogen peroxide to water and oxygen. Coenzymes 2H 2 O 2 (aq) 2H 2 O(l) + O 2 (g) catalase

56. 24.3 Amino Acids and Their Polymers 56 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. What kind of biological molecule is an enzyme? How does an enzyme act?

57. 24.3 Amino Acids and Their Polymers 57 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. What kind of biological molecule is an enzyme? How does an enzyme act? An enzyme is a protein. It acts as a catalyst—it speeds reaction time, does not affect a reaction’s equilibrium point, and is not used up by a reaction.

58. 24.3 Amino Acids and Their Polymers 58 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. An amino acid has a carboxyl group, an amino group, a hydrogen atom, and an R group bonded to a central carbon atom. Differences in the amino acid sequence result in differences in the properties of peptides. Enzymes increase reaction rates. Key Concepts

59. 24.3 Amino Acids and Their Polymers 59 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. amino acid: an organic compound having amino (—NH 2 ) and carboxyl (—COOH) groups in the same molecule; proteins are made from the 20 naturally occurring amino acids peptide: an organic compound formed by a combination of amino acids in which the amino group of one acid is united with the carboxyl group of another through an amide bond Glossary Terms

60. 24.3 Amino Acids and Their Polymers 60 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. peptide bond: the bond between the carbonyl group of one amino acid and the nitrogen of the next amino acid in the peptide chain; the structure is protein: any peptide with more than 100 amino acids Glossary Terms

61. 24.3 Amino Acids and Their Polymers 61 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. enzyme: a protein that acts as a biological catalyst substrate: a molecule on which an enzyme acts active site: a groove or pocket in an enzyme molecule into which the substrate (reactant molecule) fits; where the substrate is converted to products Glossary Terms

62. 24.3 Amino Acids and Their Polymers 62 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Proteins are polymers of amino acids and are needed for most chemical reactions in cells. BIG IDEA Chemistry as the Central Science

63. 24.3 Amino Acids and Their Polymers 63 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. END OF 24.3