Dipeptide: Definition, Formation & Structure

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  • 0:01 Overview of Amino Acids
  • 1:01 What is a Dipeptide?
  • 2:44 Lesson Summary
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Lesson Transcript
Instructor: Jennifer Gilley
Amino acids are the building blocks of proteins. Two amino acids can be joined together to make a dipeptide. This lesson will focus on what dipeptides are and how they are formed.

Overview of Amino Acids

Proteins are large molecules within our cells that have important roles in various cellular functions. All proteins are made up of individual building blocks called amino acids. Multiple amino acids can be strung together to make a protein, just like multiple bricks can be assembled to build a house. There are 21 different amino acids, and each one is a little different from one another. However, all amino acids have the same molecular backbone. Every amino acid has an amine group and a carboxyl group. An amine is a group of atoms made up of a nitrogen bound to two hydrogens. A carboxyl group is made up of a carbon that is double bonded to an oxygen and is also bound to an oxygen and a hydrogen. The part of the amino acid that distinguishes it from other amino acids is called the R group. Each amino acid has a different R group, which can be something as simple as a hydrogen (as seen in the amino acid glycine) or something that is more complex.

Structure of an Amino Acid
structure of an amino acid

What is a Dipeptide?

Different amino acids can be joined together to make a protein. The order of the amino acids determines which protein will be made. When two amino acids are joined together, a dipeptide is formed. A special chemical bond called a peptide bond holds together two amino acids. Proteins usually consist of multiple amino acids that are held together by peptide bonds. So the bigger the protein, the more amino acids and peptide bonds there are.

Now that you know what a protein is, you might be wondering how the amino acids are joined together. A process called dehydration synthesis is used to join amino acids by forming a peptide bond. During this process, a molecule of water (H2O) is removed (dehydration) in order to synthesize a dipeptide. This water molecule is composed of an oxygen and hydrogen from the carboxyl group of one amino acid and a hydrogen from the amine group of the other amino acid: O-H + H = H2O. In the example below, two glycine amino acids are being joined together using dehydration synthesis. Notice the R group of each glycine is a lone hydrogen. As you can see, a molecule of water is removed, resulting in the formation of a peptide bond.

Formation of a Dipeptide Using Dehydration Synthesis
Two amino acids are joined using dehydration synthesis

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