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