《有机化学》课程PPT教学课件（Official PPT of Organic Chemistry, 7th Edition, L. G. Wade, Jr.Pearson Education）Chapter 24 Amino Acids, Peptides, and Proteins

Organic Chemistry,7th Edition L.G.Wade,Jr. Chapter 24 Amino Acids,Peptides,and Proteins Copyright 2010 Pearson Education,Inc

Chapter 24 Copyright © 2010 Pearson Education, Inc. Organic Chemistry, 7th Edition L. G. Wade, Jr. Amino Acids, Peptides, and Proteins

Proteins Biopolymers of a-amino acids. -Amino acids are joined by peptide bond. They serve a variety of functions: ■Structure Enzymes Transport Protection ■Hormones Chapter 24 2

Chapter 24 2 Proteins ▪ Biopolymers of -amino acids. ▪ Amino acids are joined by peptide bond. ▪ They serve a variety of functions: ▪ Structure ▪ Enzymes ▪ Transport ▪ Protection ▪ Hormones

Structure of Proteins 仪carbon atom CH-C- OH a-amino group R —side chain an d-amino acid 0 0 HN-CH-C-OH H2N-CH-C-OH H2N-CH-C- OH HN-CH-C-OH HN-CH-C-OH CH3 CH2OH H CH2SH CH(CH3)2 alanine serine glycine cysteine valine several individual amino acids peptide bonds ；-NH-CH-C-NH-CH- NH一CH NH-CH- NH-CH-C -8 CH3 CH2OH H CH>SH CH(CH32 a short section of a protein Copyright 2010 Pearson Prentice Hall,Inc. Chapter 24 3

Chapter 24 3 Structure of Proteins

Amino Acids -NH2 on the carbon next to -COOH. Glycine,NH2-CH2-COOH,is simplest. -With-R side chain,molecule is chiral. -Most natural amino acids are L-amino acids,related to L-(-)-glyceraldehyde. Direction of optical rotation,(+)or(-), must be determined experimentally. Chapter 24

Chapter 24 4 Amino Acids ▪ —NH2 on the carbon next to —COOH. ▪ Glycine, NH2—CH2—COOH, is simplest. ▪ With —R side chain, molecule is chiral. ▪ Most natural amino acids are L-amino acids, related to L-(-)-glyceraldehyde. ▪ Direction of optical rotation, (+) or (-), must be determined experimentally

Stereochemistry of a-Amino Acids COOH CHO COOH H H H COOH CHO COOH H2N H HO H H2N- H CH3 CH2OH R L-alanine L-(-)-glyceraldehyde an L-amino acid (S)-alanine (S)-glyceraldehyde (S)configuration Copyright2010 Pearson Prentice Hall,Inc. Chapter 24 5

Chapter 24 5 Stereochemistry of -Amino Acids

Standard Amino Acids Twenty standard a-amino acids. Differ in side-chain characteristics: ·-H or alkyl ·Contains an-OH ■Contains sulfur Contains a nonbasic nitrogen Has -COOH -Has a basic nitrogen Chapter 24 6

Chapter 24 6 Standard Amino Acids ▪ Twenty standard -amino acids. ▪ Differ in side-chain characteristics: ▪ —H or alkyl ▪ Contains an —OH ▪ Contains sulfur ▪ Contains a nonbasic nitrogen ▪ Has —COOH ▪ Has a basic nitrogen

Essential Amino Acids Arginine (Arg) Tryptophan (Trp) -Threonine(Thr) Methionine (Met) Lysine (Lys) ■Histidine(His) Valine (Val) ·Leucine(Leu) -Phenylalanine(Phe)Isoleucine(lle) Chapter 24 7

Chapter 24 7 Essential Amino Acids ▪ Arginine (Arg) ▪ Threonine (Thr) ▪ Lysine (Lys) ▪ Valine (Val) ▪ Phenylalanine (Phe) ▪ Tryptophan (Trp) ▪ Methionine (Met) ▪ Histidine (His) ▪ Leucine (Leu) ▪ Isoleucine (Ile)

TABLE 24-2 The Standard Amino Acids Functiona Name Symbol Abbreviation Structure Point side chain is nonpolar,H or alkyl glycine G Gly HN-CH一COOH none 6.0 面 alaninc Ala H.N-CH-COOH alkyl group 6.0 H valine Val HN-CH-COOH alkyl group 6.0 leucine Leu H,N一CH一COOH alkyl group 6.0 CH,一CH-CH, CH, isoleucine H,N-CH-COOH alkyl group 6.0 CH,-CH一CH.CH1 phenylalanine Phe H,N-CH-COOH aromatic group 5.5 CH,- proline Pro HN-CH一COOH rigid cyclie structure 6.3 H. CH, CH. side chain contains an-OH serine Ser H,N-CH一COOH hydroxyl group 57 CH-OH threonine Thr H,N-CH-COOH hydroxyl group 5.6 HO-CH一CH Copyright 2010 Pearson Prentice Hall,Inc. Chapter 24 8

Chapter 24 8

TABLE 24-2 The Standard Amino Acids(continued) Functional Group lsoelectric Name Symbol Abbreviation Structure in Side Chain Point tyrosine Tyr H,N一CH-COOH phenolic-OH group 5.7 CH, OH side chain contains sulfur cysteine c Cys H,N-CH-COOH thiol 5.0 CH,-SH methionine W Met H,N-CH-COOH sulfide 5.7 CH一CH一S-CH side chain contains nonbasic nitrogen asparagine N Asn HN-CH一COOH amide 5.4 CH2-C-NH2 0 glutamine GIn H,N-CH-COOH amide 5.7 CH,一CH C一NH tryptophan W Trp H,N-CH-COOH indole 5.9 H H Chapter 24 9

Chapter 24 9

TABLE 24-2 The Standard Amino Acids(continued) Functional Group Isoelectric Name Symbol Abbreviation Structure in Side Chain Point side chain is acidic aspartic acid Asp H,N-CH-COOH carboxylic acid 2.8 CH,-COOH glutamic acid E Glu H,N- CH一COOH carboxylic acid 3.2 CH一CH一COOH side chain is basic lysine Lys H,N-CH-COOH amino group CH,-CH,-CH,-CH,一NH, arginine Arg H,N一CH一COOH guanidino group 10.8 CH2一CH2一CH,-NH C-NH, NH histidine His H,N-CH-COOH imidazole ring 7.6 essential amino acid Copyright 2010 Pearson Prentice Hall,Inc. Chapter 24 10

Chapter 24 10