What is the monomer of protein?

What is the monomer of protein?


Proteins are essential macromolecules that play a crucial role in various biological processes. They are involved in structural support, enzymatic reactions, transport, signaling, and many other functions within living organisms. But have you ever wondered what the building blocks of proteins are? In this article, we will explore the monomer of protein and its significance in the formation of these complex molecules.

The Monomer of Protein: Amino Acids

The monomer, or the basic unit, of proteins is called an amino acid. Amino acids are organic compounds that contain an amino group (-NH2) and a carboxyl group (-COOH) attached to a central carbon atom. Additionally, they have a side chain, also known as the R-group, which distinguishes one amino acid from another. The R-group can vary in structure, size, and chemical properties, giving each amino acid its unique characteristics.

There are 20 different amino acids commonly found in proteins, each with its own specific R-group. These amino acids can be classified into different groups based on the properties of their R-groups. For example, some amino acids have hydrophobic R-groups, meaning they are repelled by water, while others have hydrophilic R-groups, making them attracted to water.

Peptide Bonds and Polypeptides

When two amino acids come together, they can form a covalent bond known as a peptide bond. This bond is formed through a condensation reaction, where the carboxyl group of one amino acid reacts with the amino group of another, resulting in the release of a water molecule.

The chain of amino acids linked by peptide bonds is called a polypeptide. Polypeptides can vary in length, ranging from just a few amino acids to thousands of amino acids in length. The sequence and arrangement of amino acids in a polypeptide chain determine its unique structure and function.

Protein Structure and Function

Proteins have a hierarchical structure that can be classified into four levels: primary, secondary, tertiary, and quaternary structure. The primary structure refers to the linear sequence of amino acids in a polypeptide chain. This sequence is determined by the genetic code encoded in DNA.

The secondary structure of a protein refers to the local folding patterns that result from hydrogen bonding between nearby amino acids. The two most common secondary structures are the alpha helix and the beta sheet.

The tertiary structure is the overall three-dimensional shape of a single polypeptide chain. It is determined by various interactions between amino acid side chains, such as hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bonds.

In some cases, proteins can consist of multiple polypeptide chains, which are held together by interactions to form the quaternary structure. The quaternary structure is essential for proteins with complex functions, such as hemoglobin, which consists of four polypeptide chains.

The specific structure of a protein is directly related to its function. Proteins can act as enzymes, catalyzing chemical reactions; as antibodies, defending against foreign substances; as transporters, moving molecules across cell membranes; and in many other crucial roles within the body.


In conclusion, the monomer of protein is the amino acid. Amino acids are organic compounds with distinct R-groups that come together through peptide bonds to form polypeptides. The sequence and arrangement of amino acids determine the primary structure, which ultimately leads to the secondary, tertiary, and quaternary structures of proteins. Understanding the monomer of protein is fundamental to comprehending the complexity and diversity of these vital macromolecules.


– Nelson, D.L., Cox, M.M. Lehninger Principles of Biochemistry. 7th edition. W.H. Freeman and Company, 2017.
– Berg, J.M., Tymoczko, J.L., Gatto, G.J. Stryer, L. Biochemistry. 8th edition. W.H. Freeman and Company, 2015.