27 AAs - Class - structure polarity carbon skeleton fate and essentiality

27 AAs - Class - structure polarity carbon skeleton fate and essentiality

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Unformatted text preview: Amino Acids and Proteins: Classifications Structure, Polarity, Carbon Skeleton Fate and Essentiality HNFE 3025 Fall 2009 Amino Acids have Asymmetric (chiral) α Carbons • 19 of the 20 common amino acids have an asymmetric (chiral) α carbon atom because there are four different groups attached to this carbon. – Each of the 19 amino acids exist in two stereoisomeric forms, designated as L (levo or left) or D (dextro or right). – Only L-amino acids are used to make proteins in our bodies • D-amino acids are rare in nature 2 20 Amino Acids Used to Make Protein in Our Body: names and short forms 3 Gln • Structure – The side chain (R group) has a distinctive characteristic • Gives structure and function to polypeptides • Determines whether a given amino acid can be synthesized or must be ingested • Determines specific pathways for metabolism • 7 structural groups – Aliphatic, containing a hydroxyl group, containing an aromatic ring, containing sulfur, acidic (and their amides), basic, imino Amino Acid Classification 4 Amino Acid Structures 5 methionine (Met) isoleucine (Ile) valine (Val) leucine (Leu) aspartic acid (Asp) glutamic acid (Glu) phenylalanine (Phe) tyrosine (Tyr) tryptophan (Trp) asparagine (Asn) glutamine (Gln) histidine (His) glycine (Gly) serine (Ser) threonine (Thr) alanine (Ala) cysteine (Cys) proline (Pro) lysine (Lys) NH arginine (Arg) NH • Aliphatic – Gly, Ala, Val, Leu, Ile • Hydroxyl groups – Tyr, Ser, Thr • Sulfur containing – Met, Cys • Acidic (and their amides) – Glu, Asp (Gln, Asn) • Basic – Lys, Arg, His • Aromatic – Phe, Tyr, Trp • Imino acid – Pro Side Chain Groups 6 Aliphatic Amino Acids 7 methionine (Met) isoleucine (Ile) valine (Val) leucine (Leu) aspartic acid (Asp) glutamic acid (Glu) phenylalanine (Phe) tyrosine (Tyr) tryptophan (Trp) asparagine (Asn) glutamine (Gln) histidine (His) glycine (Gly) serine (Ser) threonine (Thr) alanine (Ala) cysteine (Cys) proline (Pro) lysine (Lys) NH arginine (Arg) NH Aliphatic Amino Acids • Contains carbon and hydrogen only • Has no net charge at physiologic pH • Glycine – Not chiral • Valine, Leucine, and Isoleucine – Branched chain amino acids 8 isoleucine (Ile) valine (Val) leucine (Leu) glycine (Gly) alanine (Ala) Amino Acids with a Hydroxyl Group 9 methionine (Met) isoleucine (Ile) valine (Val) leucine (Leu)...
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This note was uploaded on 03/23/2010 for the course HNFE 3025 taught by Professor Mwhulver during the Spring '10 term at Virginia Tech.

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27 AAs - Class - structure polarity carbon skeleton fate and essentiality

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