What Are the Subunits of a Protein Called?

Proteins are one of the most common organic molecules in biological systems and have a diverse range of functions compared with other macromolecules. They can have toxic or enzymatic activity, or they can be used for structural, regulatory, contractile, or protective elements of membranes or parts of transport and storage systems.

• Each cell in a biological system may have thousands of different proteins.
• Each of them serves a different function and has a unique structure.
• They are all linearly arranged polymers of amino acids.

A protein's shape is crucial for the way it operates. For instance, an enzyme can bind to a specific substrate at a site known as the active site. The ability of the enzyme to bind to the substrate may be compromised if this active site is altered because of regional modifications or changes in the protein's overall structure.

Understanding the primary, secondary, tertiary, and quaternary stages of protein structure is necessary to comprehend how the protein assumes its final shape or conformation.

• Primary structure: The distinctive arrangement of amino acids in a polypeptide chain is its primary structure. 
  • The primary structure of proteins is the precise arrangement of amino acids that construct their chains.
  • Every protein's unique sequence is ultimately defined by the gene that codes for it. A change in the nucleotide sequence of the gene's coding region may cause a new amino acid to be added to the expanding polypeptide chain, changing the structure and function of the resulting protein. 
  • In sickle cell anemia, a single amino acid substitution occurs in the hemoglobin beta chain, altering the structure and function of the protein. In this chain, valine specifically replaces the amino acid glutamic acid. 
  • All genetic abnormalities, such as cystic fibrosis, sickle cell anemia, albinism, and others, are caused by mutations or changes in the primary protein structures, which generate changes in the secondary, tertiary, and maybe quarterly structures.
• Secondary structure: The secondary structure of the protein is created by the local folding of the polypeptide in specific areas.
  • The proteins don't merely exist as a simple chain of polypeptides.
  • The interaction between the amine and carboxyl groups of the peptide link causes these polypeptide chains to fold.
  • This structure is seen as a long polypeptide chain. The most prevalent is the beta-pleated sheet and alpha-helix forms. Both structures are made up of an alpha-helix structure and a helix that is kept together by hydrogen bonds.
  • The oxygen atom in the carbonyl group of one amino acid forms hydrogen bonds with another amino acid located further down the chain.
  • However, specific protein chain segments may develop their local fold. These folds are significantly simpler and typically take the form of spirals, elongated shapes, or loops. Secondary elements, which refer to these regional folds, are what give proteins their secondary structure.
  • The alpha helix and beta-pleated sheet structures, which are present in most of the globular and fibrous proteins, have an important structural role.
• Tertiary structure: The tertiary structure of a polypeptide is its characteristic three-dimensional shape.
  • The structure of the polypeptide chain is partially determined by chemical interactions on the chain.
  • The secondary structure of the protein is further folded to form the tertiary structure.
  • This structure is stabilized by hydrogen bonds, electrostatic forces, disulfide connections, and van der Waals forces.
  • Two major molecular shapes, namely, fibrous and globular, are derived through the tertiary structure.
• Quaternary structure: Some proteins in nature are constructed from several polypeptides, commonly referred to as subunits, and the interaction of these subunits results in the formation of the quaternary structure.

Proteins have a wide range of functions, some of which include the following:

• Antibody: To aid in the body's defense, antibodies bind to foreign substances, such as viruses and bacteria.
• Enzyme: Nearly all hundreds of chemical reactions that occur in cells are carried out by enzymes. They also aid in the synthesis of new molecules by reading the genetic data contained in DNA.
• Messenger: Messenger proteins, such as certain hormones, transmit messages between several cells, tissues, and organs to coordinate biological functions.
• Structural component: These proteins provide structure and support for cells. On a larger scale, they also allow the body to move.
• Transport/storage: These proteins bind and carry atoms and small molecules within cells and throughout the body.