Amino Acids and Peptides

Amino Acid

Amino acids ionne at cellular pH(7.4)

• CoOH group is a radio group that can donate and accept a proton (H+)

Peptide Bond

is a covalent bond between amino acids

Atoms of a peptide bond

• share electrons unevenly

• oxygen is more electronegative than nitrogen

• polarity of the peptide bond allows hydrogen bonding between parts of a polypeptide

Hydrogen bonding

where there is bonding between a slightly positive H atom of one molecule and a slightly negative atom of another molecule or within the same molecule

Hydrogen bonding

occurs between the C=O of one amino acid residue and the N-H of another

Hydrogen bonding

is more easily broken than an ionic or a covalent bond

• often represented as a dotted line

• many hydrogen bonds together are quite strong

Peptides

A peptide is two or more amino acid residues covalently bonded together

Polypeptides

are chains of many amino acid residues joined by peptide bonds

Peptides

The three-dimensional shape of the protein is critical;

• protein conformation

• an abnormal sequence will have the wrong shape and not function normally

Fredrick Sanger

• Determined first protein sequence

• of hormone insulin - 1953

• can predict the shape of the protein