The Biology Project: Biochemistry

Large Molecules Problem Set

Problem 1: Recognition of the peptide bond

Tutorial to help answer the question

Which arrow points to a peptide bond?

equation with 5 arrows pointing to different bonds


Amino acids
The polypeptide chains of proteins are linear polymers of amino acids linked by peptide bonds. Each amino acid has an amino group (-NH2) and a carboxyl group (-COOH) that are used for peptide bond formation. Structural formula for an amino acid. Amino group and Carboxyl group identified
Peptide bonds
As shown in the diagram, the peptide bond forms between the carbon atom (C) of the carboxyl group and the nitrogen atom (N) of the amino group. The elements of water are removed as a by product of this reaction. Water (HOH) forms from the -OH of the carboxyl group of one amino acid and a hydrogen from the -NH2 group of the other amino acid.
Diagram representing the above description
Polypeptide chains
In this diagram, we visually separate the individual amino acids at the peptide bonds. Note that the backbone of the peptide is formed from a repeating pattern of the atoms N-C-C, corresponding respectively to the amino nitrogen-alpha carbon-carbonyl carbon of the individual amino acids. The groups shown as R1, R2, R3, etc represent the side chains of different amino acids.

Diagram illustrating the above description

Problem 1 Answer Problem 2

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