Biochemistry 3381A Chapter Notes - Chapter 4.1: Amphiphile, Hydrophile, Selenocysteine
11 Oct 2017
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Document Summary
Typical amino acids contain a central tetrahedral carbon atom: covalently bonded to amino and carboxyl group, bonded to h and side chain, r group give aa"s identity. In ph = 7, carboxyl is negative and amino is positive: results in zwitterion, aas are chiral, except glycine, chiral = asymmetric, 2 possible conformations for alpha-carbon, resulting in enantiomers. Amino acids can join via peptide bonds: amino and carboxyl groups react in head-to-tail fashion, being hydrolyzed, releasing water, forming covalent amide linage, equilibrium favors peptide bond hydrolysis, must couple peptide bond formation (indirectly or with energy input) Amino acids 21 and 22 and more: beyond 20, they occur, selenocysteine, pyrrolysine lysine derivative, both incorporate into proteins from adapted rna molecules, create novel structural/chemical features. Several amino acids occur only rarely in proteins: produced by modifications of 1 of the 20 aas already in a protein, hydroxylysine, hydroxyproline, proglutamic acid, gamma-carboxyglutamic acid, gamma-aminobutyric acid (gaba, histamine, serotonin, epinephrine.
