Proteins – part 1

Proteins Our third big biomolecule Review: –the carbohydrate base unit is the _____________ –the lipid base unit is the ________________ (for the hydrolyzable ones anyway!)

Proteins >50% of the dry weight of the body 100,000+ compounds Types of proteins: –Catalytic –Transport –Regulatory –Structural –Contractile –Protective –Storage

Protein unit: the amino acid Amino acids –20 required by mammals –10 essential must be from diet –Four categories: Nonpolar neutral Polar neutral Polar acidic Polar basic –Natural amino acids are ____stereochemistry!

Practice drawing: Glycine Valine Cysteine

Amino acids in solution Zwitterions pI and pH

Peptides: chains of amino acids 1 amino acid + 1 amino acid = 1 dipeptide 1 a.a. + 1 a.a. + 1 a.a. = 1 tripeptide Oligopeptide Polypeptide Proteins

Formation of the peptide bond dipeptide

Peptide sequences Name from N terminal to C terminal using three letter abbreviations –gly-cys-ala Direction matters !! –gly-cys-ala is different from ala-cys-gly Possible constitutional isomers for a given number of different amino acids = n!

Amino acid exercise: Three groups: draw out your share of the β-endorphin, met-enkephalin, and leu- enkephalin amino acid sequence Draw from left to right, N-terminus to C- terminus, your amino acids on notecards using colored stickers Link the notecards together, constructing correct peptide bonds. Overall charge at physiological pH:______

Extra credit exercise (5 pts)