Amino Acids and Peptides - Lecture Slides | CHEM 3550, Study notes of Biochemistry

Download Amino Acids and Peptides - Lecture Slides | CHEM 3550 and more Study notes Biochemistry in PDF only on Docsity! Chapter Three Amino Acids and Peptides Part II Spring 2011 Dr. JDavis Chapter Outline 3.1 Amino Acids (AA) exist in a 3-D world 3.2 Structure/Properties of Amino Acids • AA sides character • Nonpolar side chains • Polar side chains • Neutral side chains • Carboxyl groups/ basic side chains 3.3 Amino acids as Acids and Bases 3.4 Peptide Bonds 3.5 Peptides with biological activity. • Also: A few Miscellaneous topics Formation of Peptide bonds • Two α-amino acids link together forming Amide bonds or Peptide Bonds via removal of H2O. • Forms a dipeptide, etc. • Recall: a condensation reaction [loss of water]. Fig. 3-10, p. 78 Resonance structure of the Peptide group • Partial double-bond character and planar (rigid) nature of peptide group determines the nature of the 3-D structure of proteins (More in Chap 4). O N Peptides (Some terms/definitions to know) • Peptide: a short polymer of amino acids (< 10?) joined by peptide bonds; • Peptides classified by number of amino acids in chain. • Each additional AA in the chain called an amino acid Residue. • Dipeptide: molecule containing two amino acids joined by a peptide bond. • Tripeptide: molecule containing three amino acids joined by peptide bonds. • Polypeptide: macromolecule containing > ~10+ amino acids joined by peptide bonds. • Protein: biological macromolecule of molecular weight ~ 5000 daltons or greater; consisting of one or more polypeptide chains A Short Pentapeptide: Gly-Glu-Val-Ser-Lys Gly - Glu -Val - Ser – Lys (Arrows indicate locations of amide bonds) Fig. 3-11, p. 79 Carnosine – a muscle tissue dipeptide **Some Biologically Important Peptides Biochemical Connections: p 79 • Branched-chain amino acids • Essential AA (cannot be synthesized in vivo) • Protein Supplements • Val, Ile, Leu, etc. • Glutamic Acid (Monosodium glutamate) • Flavor enhancer in Chinese food • Physiologically active (allergies)?? • Histidine • Precursor for Histamine, a potent vasodilator • Histamine: a target in antihistamine drugs * Other Important Small Peptides Oxytocin and Vasopressin • Pituitary gland hormones. • Cyclic nonapeptides [9 AA] with disulfides between cysteine amino acid residues. 1. Oxytocin: stimulates uterine contractions during labor. 2. Vasopressin: • An antidiuretic hormone [ADH]). • Vasopressin stimulates water reabsorption in the kidneys. • See Next slide. * Where’s the carboxy-terminus? + + Heat H;N get) } Gln } Gln S. S \ a Cys——Asn 0 LeFiaoy t NH, p(t} ly C NE Vasopressin Oxytocin Figure 3-11¢ Concepts in Biochemistry, 3/¢ Figure 3-11b Conceptsin Biochemistry, 3 192006 John Wiley & Sons ©2006 John Wiley & Sons  * Where’s the carboxy-terminus? + + Heat H;N get) } Gln } Gln 5 | 5 | \ Cys —Asn Cys——Asn h(n) Gly ro-{irgy al Vasopressin Oxytocin Figure 3-11¢ Concepts in Biochemistry, 3/¢ Figure 3-11b Conceptsin Biochemistry, 3 192006 John Wiley & Sons ©2006 John Wiley & Sons INSULIN: An important small protein • Pancreatic hormone • ~ 51 amino acids. • Structure: 2 polypep- tide chains connected via 2 disulfide bonds [Cysteine]. • Insulin regulates carbohydrate metabolism. APPENDIX Group I Hydrophobic NH CH, —C—H coo Alanine CH; NH CH—C—H ee CH; coo” Valine a CHa NH fe —CH2 —C—H CH; coo Leucine NH CH,—CH,—CH—C—H CH; COOo7 Isoleucine He aaet Hoo", coo HaC__ He Proline NH CH3—S—CH,—CH,—C__H coo Methionine ee ron coo Phenylalanine Nie G—CH2— © —H noe coo H Tryptophan NH H—C—H CGOUOe Glycine Group II Polar, uncharged NH HO— al H coo” Serine NHS CH,— CH—C—H OH COO; Threonine oe HS—cCH,—C—_H coo- Cysteine ee wo < >on Fn CoO Tyrosine NH NH a CHC Er. iS coo Asparagine NH Ht a a C—CH2—CH2— C—H 3 é Glutamine Figure 3-5 Concepts in Biochemistry, 3/e © 2006 John Wiley & Sons | sco coo A Histidine Group IIT Polar, charged Cl NH Ny C— CH,— CH ra — SOO m Aspartate -o NHS pcre cn — C—H oc coo Glutamate NH 4 HaN—CH>— CH2— CH»— CHs—C—H coo” Lysine NH. NH io —CH2— CHs—CH,— C-—_H NWH2 coo” WH Arginine