BL/CH 401 Lecture #5 - Protein Primary Structure

1. Peptide Bonds, Peptides and Proteins

Proteins are sometimes called Polypeptides, since they contain many Peptide Bonds

{*Figure 1*}

The peptide bond is an amide bond

{*Figure 2*}

Water is lost in forming an amide bond.

(See Lecture 4 Fig. 18 & 19 for discussion of amide bond character).

Comparison of an amino acid, a dipeptide and a tripeptide:

{*Figure 3*}

Amino Acid = Gly; dipeptide = Gly-Ala; tripeptide = Gly-Ala-Ser

Peptides = Mini-Proteins

{*Figure 4*}

A pentapeptide -- GlyAlaSerPheGln

1st amino acid is always written on the left and called the Amino terminal, since it is always the only amino acid of the peptide with a free alpha-amino group. Last amino acid is always written on the right and called the Carboxyl terminus, since it is always the only amino acid of the peptide with a free alpha-carboxylic acid group.

Full structure of a Protein

{*Figure 5*}

Amino acid sequence of a Protein.

©Wilbur H. Campbell, 1995, 1996; wcampbel@mtu.edu

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