BioChem Ch. 3 Amino acids and Peptides

BioChem Ch. 3 Amino acids and Peptides - 4 Peptide bond...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
CHapter 3- Amino Acids and Peptides I. The Amino Acids in Proteins A. General structure of amino acids 1. alpha-carbon a. hydrogen b. carboxyl group c. amino group d. side chain (variable) 2. Side Chain (R-group) determines reactivity 3. Chiral alpha-carbon (except glycine) a. D-and L- amino acids (enantiomers) b. only L-isomers used to make proteins in nature B. Classification of amino acids based on R-groups (side chains) 1. Nonpolar (hydrophobic) 2. Polar and Neutral 3. Charged-Acidic 4. Charged -Basic Know Table 3.1 C. Properties of Amino Acids 1. White, crystalline solids 2. High melting points 3. Water-soluble 4. Dipolar ionic species at pH 7.4 (Zwitterion) a. aqueous solutions conduct electricity b. Behave like salts (ionic compounds) 5. Acid-base properties a. Predicting electrical charges at a given pH
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
b. pKa values (Table 3.2) c. Titration curves D. Reactivity 1. Acid-base reactions 2. Ester formation (Ser, Thr, and Tyr) 3. Disulfide bond formation (Cys)
Background image of page 2
Background image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 4. Peptide bond formation II. Peptides A. Peptide Bond Formation 1. Condensation reaction 2. Residue: single amino acid 3. Polypeptide: 10-100 amino acids 4. Protein: more than 100 amino acids B. Molecular Weights 1. Average MW of amino acid=110 2. MW of proteins = 220-220,000 1 amu = 1 dalton C. Termini 1. Amino (N-terminus) 2. Carboxyl (C-terminus) D. The chemical and physical properties of proteins depend on their amino acids. 1. Determining net charge at a given pH a. Use pKa values to obtain charges on side chains b. Include charges at termini c. add charges 2. Microenvironment can affect properties of nearby side chains 3. Isoelectric point (pl) = pH when molecule has no net charge E. Physiologically Active Peptides 3aa 1. Glutathione -scavenger for oxidizing agents 5aa 2. Enkephalin - brain (pain relievers) 3. Oxytocin - contraction of uterus : milk flow 9aa 4) Vasopressin - blood pressure...
View Full Document

Page1 / 3

BioChem Ch. 3 Amino acids and Peptides - 4 Peptide bond...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online