Proteins are made of amino acids that join together in chains called polypeptides. Peptide bonds hold the blocks together. Polypeptides can perform functions on their own or join with others to form proteins. They are produced by cells reading genetic instructions and translating them into the correct amino acid sequence.
Proteins are made up of building blocks called amino acids. When two or more amino acids join together in a chain, they can be called polypeptides. Each bond between amino acids, where energetic attraction holds the blocks together, is a peptide bond. Polypeptides perform many functions in the body.
Amino acids are small molecules that are essential building blocks in biology. Many biological functions rely on the action of a protein or polypeptide. Generally, very short polypeptides are usually called peptides and very long ones, with more than about 100 amino acids, are called proteins. All proteins fall under the polypeptide group, but some polypeptides do not meet the criteria to be a protein.
The peptide part of the name comes from the type of bond between two blocks of amino acids. Each amino acid has one end called an alpha-carboxylic group and another end called an alpha-amino group. These two groups have different chemical properties.
An alpha-carboxyl tends to bind to an alpha-amino and vice versa. A single amino acid, therefore, tends to attach itself to another amino acid in a specific way, somewhat like a person holding another person’s hand. One uses his right hand and the other uses his left hand to complete the binding. This form of bond is a peptide bond and when the two molecules join together, they produce one molecule.
Joining two amino acids requires energy. The body supplies this energy when it needs to produce new polypeptides for biological use. After the two amino acids are bonded together, the bond is quite stable and does not break easily.
Polypeptides contain many of these amino acids stuck together in a straight line, much like a line of people holding hands with each other. Typically, a polypeptide chain also has chains that attach laterally at certain points. A polypeptide can contain up to 2,000 individual amino acids.
In the body, polypeptides can perform functions as they are. They may also need to join with another to form a new protein with a biological function. Sometimes, a single polypeptide is created as a product of large cells and then the cell uses an enzyme to break it down into functional portions.
Polypeptides are first produced when a cell reads its genetic instructions and translates that information into the amino acid sequence. Each gene codes for a particular product, and the necessary amino acids are collected and glued together in the correct order. The sequence is essential for the polypeptide to function properly, otherwise it cannot interact properly with its targets.
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