Polypeptide Chain: Definition, Structure & Synthesis

Polypeptide Chain: Definition, Structure & Synthesis
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  • 0:00 What Are Proteins?
  • 1:19 Amino Acid Structure
  • 2:25 Making a Polypeptide Chain
  • 3:36 Lesson Summary
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Lesson Transcript
Instructor: Jennifer Gilley
Proteins play important roles within our cells. Each protein is made up of at least one polypeptide chain. This lesson discusses the synthesis of polypeptide chains and emphasizes the relationship between its structure and function.

What Are Proteins?

Your cells use various types of molecules in order to perform their daily functions. One of the most important classes of molecules are called proteins. Proteins are molecules that have several different functions within the cell. Such functions include transporting things in and out of the cell, speeding up chemical reactions, and helping cells recognize and join to one another. Therefore, proteins are really versatile molecules that can be used for multiple purposes. Just like a Swiss army knife has multiple tools that can be used in different ways, proteins have different structures that specify their particular function.

Proteins consist of one or more polypeptide chains. Each polypeptide chain consists of smaller sub-units or amino acids that are linked together. Amino acids serve as the building blocks of polypeptides, and polypeptides serve as the building blocks of proteins. Think of an individual amino acid as a paper clip. When you link several paper clips together, you make a paper clip chain. Joining dozens of amino acids together makes a polypeptide chain. A polypeptide chain can serve as a protein on its own. However, lots of proteins are made up of several polypeptide chains.

Amino Acid Structure

There are 20 naturally-occurring amino acids, and each one is a little different. All amino acids have the same basic structure; however, something called an R group distinguishes one amino acid from another. Here, you can see the chemical structures of all 20 amino acids.

Although the black parts of each amino acid are the same, the R groups (shown in brown) are all different from one another. The differences in these R groups are what help give a polypeptide chain its structure and, ultimately, its function.

The order and arrangement of these amino acids in a polypeptide chain will produce different chemical structures. A protein's structure is essential to its function. So, multiple amino acids can be strung together to make a particular polypeptide chain with a specified function. Similarly, letters of the alphabet can be rearranged to make different words, each with its own meaning. This image is a simple representation of a polypeptide chain made of several different amino acids. Each pattern represents a different amino acid.

Making a Polypeptide Chain

You know now that a polypeptide chain consists of a bunch of different amino acids linked together. But, how are these amino acids linked together? Actually, the process called dehydration synthesis is not that difficult to understand.

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