Peptides and proteins are both composed of the same primary component; amino acid. However, proteins have a much larger structure than peptides. Proteins are an aggregation of long chains of peptides in the form of polypeptides, while peptides are a sequence of amino acids.

Peptides and proteins are fundamental components of the human cells that play important biological functions. They are both essential organic compounds found in animal and plant cells, performing various functions. For example, proteins help shape cells, and they also respond to signals which are transmitted from the extracellular environment. Recombinant proteins like Shenandoah Biotech / human tpo recombinant protein helps with gene expression and RNA translation.

To fully understand the difference between proteins and peptides, one must first understand their makeup.

What Is A Peptide?

A peptide is a molecular structure made up of strings of simple amino acids. There are several types of peptides depending on the amount of amino acid chain formed. Some of the most common types include Oligopeptides, Polypeptides, Dipeptides, Tripeptides, and Tetrapeptides.

Dipeptides peptides have two amino acids, tripeptides have three amino acids, and tetrapeptides have four chains of amino acids. Oligopeptides are aggregations of few amino acid chains, and polypeptides are long chains of 20 to 50 amino acids. It’s essential to know that every amino acid in a peptide is attached to linear chains, forming peptide bonds. The primary function of peptides in biology is to ensure that the activities of other molecules are regulated.

What Is A Protein?

Proteins are essential components of the human cell and one of the four main biological macromolecules present in the body. They are molecules in the body that perform structural and functional duties. Proteins are made up of a collection of series of amino acids. Typically, the type of protein formed is dependent on the number of amino acids that form the protein and the information encoded in the genes.

Protein Structures

The primary, secondary, tertiary, or quaternary protein structures are made up of a single polypeptide chain. Primary proteins are made up of linear polypeptides, while the structure of secondary proteins is alpha helices and beta sheets. The tertiary structures of proteins form both filamentous proteins and globular proteins because of the formation of hydrophilic interactions and hydrophobic interactions, hydrogen bonds, disulfide bridges, ionic bonds, etc. When two or more polypeptide chains are combined, they form the quaternary protein structure.

Similarities Between Peptide And Protein

  • Protein and peptides are both organic compounds found in the cell.
  • They are both composed of amino acid
  • The amino acids of both proteins and peptides form peptide bonds
  • They both undergo phosphorylation glycosylation, sulfonation, hydroxylation, palmitoylation, etc.
  • Both organic compounds perform specific functions for the cell.

Difference Between Peptides And Proteins


Peptides are short chains of amino acids that are connected by peptide bonds in a sequence. In contrast, proteins are aggregations of amino acids performing several functions inside the cell.

Number of Amino Acids

Peptides are short chains of amino acids with not more than 50 amino acids, while proteins are polypeptides made up of more than 50 amino acids.

Types of Amino Acids

Proteins are made up of only essential amino acids only. In contrast, peptides are made up of both essential amino acids and several other naturally occurring amino acids.

Structural Organization

Although various structures of peptides have been observed, however, most peptides will only form a straight chain of amino acids. In contrast, proteins form secondary, tertiary, and quaternary structures.


The bonds that occur between the amino acids in peptides are strictly peptide bonds. In contrast, the kind of bonds that occur between the amino acids of protein's polypeptide chains are hydrogen bonds, disulfide bonds, etc.


Proteins and peptides differ in function. Functionally, proteins play the role of essential structural molecules, hormones, enzymes, etc., which help in regulating cellular activities, etc. Peptides, on the other hand, are involved with the regulation of the activities of molecules, including proteins.


Both protein and peptides have their applications in various fields and industries. For example, in the health sector, peptides are actively being used in the production of some medications, especially those that have to do with the skin. There have also been recorded applications of peptides in the agricultural sector. Proteins, on the other hand, are essential macronutrients that the body can not do without. Protein molecules are necessary for the building and maintenance of muscles and tissues in the human body.