Difference between Peptides and Proteins

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A peptide is found in every cell and tissue of the body. It is an essential cellular component and forms a wide range of functions. It is made up of a short chain of amino acids. Usually, the chain includes two or more amino acids. The functions that peptides play will depend on the type and combination of amino acids it consists of. Peptides often act like hormones because they carry and send information from one tissue to another. Peptide hormones can be found in the stomach, brain, intestine, and glands. It helps in the regulation of appetite and blood sugar.


Amino acids are essential building blocks of peptides and proteins. There are 20 kinds of amino acids that play different roles in the body, including nutrient absorption, immune function, tissue growth, muscle repair, and energy production.


Proteins are large molecules that are made up of fifty or more amino acids. The composition and sequence of the amino acid will dictate the protein’s function.


Proteins do a lot of the heavy lifting in cells. Here are a few examples of protein functions:

  • Form cellular structure

  • Transports molecules and atoms

  • Form antibodies

  • Send messages

  • processes between organs, tissues, and cells

  • Form enzymes

  • Form new molecules


Overall, proteins help regulate and form the body’s tissues and organs.


Peptides and proteins have similarities in form and function. Functionally, both play vital roles in a wide array of biological functions. They serve as the body’s building blocks. Structurally, amino acid chains make up peptides and proteins. For both, the amino acid chains are held together by peptide bonds.


For peptides and proteins, size shows the number of amino acids it contains. Here’s how they differ:

  • Peptides – 2-10 amino acids

  • Polypeptides (a subcategory of peptides) – 10-50 amino acids

  • Proteins – 51 and more amino acids


Essentially, one or more polypeptides make up proteins. So, a protein is actually a large peptide.


Apart from that, since proteins provide cells with their shape and structure, peptides are usually less defined. Proteins are more complex and can have multidimensional structures and complex conformations known as secondary, tertiary, and quaternary structures.


Proteins can perform more complicated functions than peptides because they contain more amino acids. Keep in mind that it’s the combination of amino acids dictates the functions of proteins and peptides.


Proteins and peptides are fundamental components of cells that carry out important biological functions. Proteins give cells their shape, for example, and they respond to signals transmitted from the extracellular environment. Certain types of peptides play key roles in regulating the activities of other molecules. Structurally, proteins and peptides are very similar, being made up of chains of amino acids that are held together by peptide bonds (also called amide bonds).


Peptides, however, may be subdivided into oligopeptides, which have few amino acids (e.g., 2 to 20), and polypeptides, which have many amino acids. Proteins are formed from one or more polypeptides joined together. In fact, some researchers use the term peptide to refer specifically to oligopeptides, or otherwise relatively short amino acid chains, with the term polypeptide being used to describe proteins, or chains of 50 or more amino acids.

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