Amino one another. However, all amino acids have

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.

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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

Keep in mind that there are multiple different dipeptides. A dipeptide can consist of any combination of two amino acids. In other words, a dipeptide doesn’t have to be made from the same amino acids as in the example you just looked at. Here, you can see another example of a dipeptide.

This one is a combination of glycine and a different amino acid that has a -CH3 as its R group, known as alanine.

Another Example of a Dipeptide
Another example of a dipeptide

Lesson Summary

Let’s review. Proteins are molecules that are essential for normal cellular functions. They consist of multiple amino acids, which are held together by peptide bonds.

Every amino acid has an amine group and a carboxyl group. Only the R group of an amino acid distinguishes it from all the other amino acids. A process called dehydration synthesis is used to join two amino acids together. A dipeptide is a short protein consisting of only two amino acids linked together by one peptide bond. Multiple different dipeptides can be made using dehydration synthesis, which removes a molecule of water, resulting in the formation of a peptide bond.

Dipeptides: Key Terms

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  • Amino acids: building blocks that make up proteins
  • Dipeptide: short protein of two amino acids held together by a peptide bond
  • Peptide bonds: special chemical bonds that hold amino acids together
  • Carboxyl group: a group of atoms made up of a carbon that is double bonded to an oxygen and is also bound to an oxygen and a hydrogen
  • Amine group: group of atoms made up of a nitrogen bound to two hydrogens
  • R group: component of an amino acid that distinguishes it from other amino acides
  • Dehydration synthesis: process for bonding amino acids by creating a peptide bond

Learning Outcomes

After students finish this lesson, they should be able to:

  • Describe what amino acids are
  • Define dipeptide
  • Explain how dipeptides are formed
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